[Federal Register: August 30, 2006 (Volume 71, Number 168)]
[Proposed Rules]               
[Page 51549-51565]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]

[[Page 51549]]



Fish and Wildlife Service

50 CFR Part 17

Endangered and Threatened Wildlife and Plants; Petition to List 
the Sonoran Desert Population of the Bald Eagle as a Distinct 
Population Segment, List that Distinct Population Segment as 
Endangered, and Designate Critical Habitat

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 90-day petition finding.


SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
90-day finding on a petition to reclassify the Sonoran Desert 
population of the bald eagle (Haliaeetus leucocephalus) in central 
Arizona and northwestern Mexico as a distinct population segment, list 
that distinct population segment as endangered, and designate critical 
habitat for that distinct population segment under the Endangered 
Species Act of 1973, as amended (Act). On the basis of a review of the 
information contained within the petition, we find that the petition 
does not provide substantial scientific or commercial information 
indicating that the petitioned action may be warranted. Therefore, we 
will not initiate a further status review in response to this petition. 
We ask the public to submit to us any new information that becomes 
available concerning the status of this population of the bald eagle or 
threats to it.

DATES: The finding announced in this document was made on August 29, 

ADDRESSES: The complete file for this finding is available for 
inspection, by appointment, during normal business hours at the Arizona 
Ecological Services Office, 2321 West Royal Palm Road, Suite 103, 
Phoenix, AZ 85021-4951. Please submit any new information, materials, 
comments, or questions concerning this species or this finding to the 
above address.

telephone, 602-242-0210; facsimile, 602-242-2513.



    Section 4(b)(3)(A) of the Endangered Species Act of 1973, as 
amended (16 U.S.C. 1531 et seq.) (Act), requires that we make a finding 
on whether a petition to list, delist, or reclassify a species presents 
substantial scientific or commercial information to indicate that the 
petitioned action may be warranted. We are to base this finding on 
information provided in the petition. To the maximum extent 
practicable, we are to make this finding within 90 days of our receipt 
of the petition, and publish our notice of this finding promptly in the 
Federal Register.
    Our standard for substantial information within the Code of Federal 
Regulations (CFR) with regard to a 90-day petition finding is ``that 
amount of information that would lead a reasonable person to believe 
that the measure proposed in the petition may be warranted'' (50 CFR 
424.14(b)). If we find that substantial information was presented, we 
are required to promptly commence a review of the status of the 
species, if one has not already been initiated under our internal 
candidate assessment process.
    In making this finding, we relied on information provided by the 
petitioners and evaluated that information in accordance with 50 CFR 
424.14(b). Our process of coming to a 90-day finding under section 
4(b)(3)(A) of the Act and Sec.  424.14(b) of our regulations is limited 
to a determination of whether the information in the petition meets the 
``substantial information'' threshold.
    On October 6, 2004, we received a formal petition, dated October 6, 
2004, from the Center for Biological Diversity (Center), the Maricopa 
Audubon Society, and the Arizona Audubon Council requesting that the 
bald eagle population found in the Sonoran Desert (as defined by Brown 
1994) or, alternately, in the upper and lower Sonoran Desert (as 
defined by Merriam) be classified as a distinct population segment 
(DPS) and this DPS be reclassified as an endangered species, in 
accordance with the Act. The petition also requested that critical 
habitat be designated concurrently for the DPS.
    Because the Sonoran Desert described by Brown (1994) encompasses a 
different geographic area than that defined as upper and lower Sonoran 
Desert by Merriam, the Service requested clarification on the intended 
geographic boundaries for the Sonoran population on February 11, 2005. 
The petitioners responded with clarification on March 5, 2005, 
requesting that we consider in the DPS analysis those bald eagles 
nesting along riparian areas in the Sonoran Desert in Arizona and 
northwestern Mexico. At that time, further action on this petition was 
precluded by higher listing priorities. On January 19, 2006, we 
received from the Center a 60-day Notice of Intent (NOI) to sue the 
Service for failure to respond to the petition within the statutory 
timeframe. On March 27, 2006, the Center and the Maricopa Audubon 
Society filed a lawsuit against the U.S. Department of the Interior 
(DOI) and the Service for failure to make a finding on the petition 
within 90 days.

Species Information

    The bald eagle (Haliaeetus leucocephalus) is the only species of 
sea eagle native to North America. Literally translated, H. 
leucocephalus means white-headed sea eagle (USFWS 1995, p. 36000). Bald 
eagles are birds of prey of the Order Falconiformes and Family 
Accipitridae. Bald eagles vary in length from 28 to 38 inches (71 to 97 
centimeters), weigh between 6.5 to 14 pounds (2.9 to 6.4 kilograms), 
and have a 66 to 96 inch (1.8 to 2.6 meter) wingspan (Arizona Game and 
Fish Department (AGFD) 1999, p. 3). Distinguishing features include a 
yellow hooked bill and yellow unfeathered legs and feet. Adults of the 
species have a dark brownish-black body color, black talons, and a 
white head, neck, and tail. Immature bald eagles are mostly dark brown 
and lack a white head and tail until they reach approximately 5 years 
of age (AGFD 2006, pg. 3).
    Gerrard and Bartolotti (1988, p. 2) note that bald eagles are 
believed to have nested on both coasts, along all major rivers and 
large lakes in the interior from Florida to Baja California in the 
south, and north to Labrador and Alaska. The species is known to have 
bred in every State and province in the United States and Canada except 
Hawaii (Hunt et al. 1992, p. A-9).
    Hunt et al. (1992, pp. A-11 and A-12) summarized the earliest 
records from the literature for bald eagles in Arizona. Coues noted 
bald eagles in the vicinity of Fort Whipple in 1866 (now Prescott), and 
Henshaw reported bald eagles south of Fort Apache in 1875. Bent 
reported breeding eagles at Fort Whipple in 1866 and on the Salt River 
Bird Reservation (since inundated by Roosevelt Lake) in 1911. Breeding 
eagle information was also recorded in 1890, near Stoneman Lake by S.A. 
Mearns. Additionally, there are reports of bald eagles along rivers in 
the White Mountains from 1937, and reports of nesting bald eagles along 
the Salt and Verde Rivers as early as 1930.
    The bald eagle population of the Southwest Recovery Region, as 
identified in the final recovery plan for the species, reaches 
throughout Oklahoma and Texas west of the 100th meridian, all of New 
Mexico and Arizona, and the area of California bordering the Lower 
Colorado River (USFWS 1982, p. 1). The vast majority

[[Page 51550]]

of these breeding bald eagles are found within the State of Arizona. 
The occurrence of breeding bald eagles in the State of New Mexico is 
very limited (USFS 2004, p. 153). In 2001, the New Mexico Department of 
Game and Fish (NMDGF) reported the occurrence of four bald eagle nest 
sites, all on private lands, in New Mexico.
    Nationwide, bald eagles are known to nest primarily along seacoasts 
and lakeshores, as well as along banks of rivers and streams 
(Stalmaster 1987, p. 120). In the Southwest, bald eagle breeding areas 
(BA) (eagle nesting sites and the area where eagles forage) are located 
in close proximity to a variety of aquatic sites, including reservoirs, 
regulated river systems, and free-flowing rivers and creeks. The term 
``BA'' is used to define eagle nesting sites and the area where they 
forage. In the Southwest, nests are placed mostly on cliff edges, rock 
pinnacles, and in cottonwood trees. However, artificial structures, 
junipers, pinyon pines, sycamores, willows, ponderosa pines, and snags 
of these trees also have supported eagle nests (AGFD 2006, p. 4).
    In Arizona, the majority of nests are located in the Upper and 
Lower Sonoran Life Zones (zones of plant and animal life associated 
with a given elevation), including the riparian habitats and transition 
areas of both zones (Hunt et al. 1992, p. A-17). Representative 
vegetation of these life zones includes Arizona sycamore (Platanus 
wrightii), blue paloverde (Parkinsonia florida), cholla (Opuntia spp.), 
Fremont cottonwood (Populus fremontii), Gooding willow (Salix 
gooddingii), mesquite (Prosopis spp.), saguaro (Carnegiea gigantea), 
and tamarisk or salt cedar (Tamarix pentandra; an exotic species) 
(Brown 1994, p. 200).
    Historical evidence to document bald eagles nesting in New Mexico 
is lacking, although unverified reports suggest one or two pairs may 
have nested in southwestern New Mexico prior to 1928. In the mid-1980s, 
a pair established a territory in Colfax County in an area where bald 
eagles concentrated in winter, and in 1987, an active nest was 
discovered nearby which produced two fledglings that year. In 1988, an 
active nest was discovered in Sierra County, also in an area of 
wintering eagle concentration; the nest fledged one young that year. 
Through 1999, those two nests together fledged a minimum of 31 young, 
with Colfax County being one of the more productive nests in North 
America. Additional nesting activity was recorded elsewhere after the 
mid-1980s, always in areas of wintering concentrations, including in 
San Juan, Rio Arriba, Quay, and Sierra counties. However, in each 
instance, eagles built nests only to abandon the effort prior to egg 
laying; such ``practice'' nests are not uncommon among inexperienced 
adults. In 1998, two additional nests were discovered in Colfax County, 
and each fledged young in both 1998 and 1999 (five young total) 
(Williams 2000, abstract).
    Bald eagles are long-lived bird species. Southwestern bald eagles 
are known to exceed 12 years of age (USFWS 1999, p. 36454; Hunt et al. 
1992, p. A-v). Bald eagles primarily eat fish, but they will also eat 
amphibians, reptiles, birds, small mammals, carrion (dead animals), and 
carcasses of large mammals (cows, elk, deer, etc.). Their food habits 
can change daily or seasonally, but when a choice is available, bald 
eagles invariably select fish over other prey. Bald eagles will 
scavenge, steal, or actively hunt to acquire food. Carrion constitutes 
a higher proportion of the diet for juveniles and subadults than it 
does for adult eagles. Bald eagles are primarily sit-and-wait hunters, 
perching in trees in order to detect available prey (Stalmaster 1987, 
p. 104).
    Eagles in the Southwest frequently construct nests on cliffs. By 
1992, of the 111 nest sites known, 46 were in trees, 36 on cliffs, 17 
on pinnacles, 11 in snags, and 1 on an artificial platform (Hunt et al. 
1992, p. A-17). However, for breeding areas where both cliff and tree 
nests were available, one study found that cliff nests were selected 73 
percent of the time, while tree nests were selected 27 percent of the 
time (Hunt et al. 1992, p. A-17). Additionally, eagles nesting on 
cliffs were found to be slightly more successful in raising young to 
fledgling, though the difference was not statistically significant. 
Nests may be used year after year. Hunt et al. (1992, p. A-20) 
determined the mean diameter of nests was 5 feet (156 centimeters).
    Food strongly influences bald eagle productivity (Newton 1979, pp. 
95-96, 101-106; Hansen 1987, p. 1389). A female's health in the months 
preceding egg laying can affect egg production, and the prey 
availability during the breeding cycle affects the survivorship of 
nestlings and post-fledging juveniles. Thus, any factor affecting the 
adults' ability to acquire food can influence productivity and adult 
survivorship (Newton 1979, pp. 95-96, 101-106). The most common fish 
eaten in the Southwest are Sonora and desert suckers; channel and 
flathead catfish; common carp largemouth, smallmouth, yellow, and white 
bass; and black crappie. Less common are roundtail chub, green sunfish, 
bluegill, tilapia, and rainbow trout (USFWS 1982, p. 11; AGFD 1999, p. 
6). Prey availability has decreased on the upper Salt River in Arizona. 
The introduction of predatory flathead catfish in the late 1970s nearly 
extirpated native fish populations. Flathead catfish, while available 
as bald eagle prey when smaller, grow to large sizes (up to 50 pounds, 
or 22.6 kilograms) making them too large for a prey item. Flathead 
catfish populations have increased while other fish species have 
decreased (AGFD 2006, p. 19). Productivity for the four bald eagle BAs 
on the upper Salt River decreased from 1.12 young per year per occupied 
BA in the 1980s to 0.29 young per occupied BA in the 1990s.
    Bald eagles in the Southwest establish their breeding territories 
in December or January and lay eggs in January or February, which is 
early compared to bald eagles in more northerly areas (Stalmaster 1987, 
p. 63). Hunt et al. (1992, p. C-16) indicate that this may be a 
behavioral adaptation so that chicks can avoid the extreme desert heat 
of midsummer and adults can take advantage of food resources for the 
rearing of eaglets. Young fledgling eagles can remain in their nest 
area though June, learning how to fly and land, while still being 
primarily fed by adult eagles (Hunt et al. 1992, pp. C-6 and C-7).
    About 45 days after leaving the nest, young southwestern bald 
eagles migrate to Canada, northern California, Idaho, Montana, North 
and South Dakota, Oregon, Washington, and Wyoming (Hunt et al. 1992, 
pp. A-104 through A-114), returning to Arizona in the fall of the same 
year. They are known to repeat this behavior for a minimum of 2 years 
(Hunt et al. 1992a-112; p. A-122-A-123). Resident adult bald eagles 
often stay in their BAs year-round, although local, short-term 
migrations are common (AGFD 1999, p. 6).
    The first major decline in bald eagle populations began in the mid- 
to late-1800s, when widespread shooting for feathers and trophies led 
to extirpation of eagles in some areas. Carrion treated with 
strychnine, thallium sulfate, and other poisons were used as bait to 
kill livestock predators and ultimately killed many eagles as well. 
These and other factors contributed to a reduction in bald eagle 
numbers through the 1940s (USFWS 1999, p. 36455). In the late 1940s, 
the use of dichloro-diphenyl-trichloroethane (DDT) and other 
organochlorine compounds became widespread. While DDT was initially 
sprayed along coastal and other wetland

[[Page 51551]]

areas for mosquito control, it later was used as a general crop 
insecticide. DDT accumulated in individual bald eagles that had 
ingested contaminated prey, and reproductive success plummeted (USFWS 
1999, p. 36455). In the late 1960s and early 1970s, it was determined 
that dichlorophenyl-dichloroethylene (DDE), a breakdown product of DDT, 
accumulated in fatty tissues of adult female eagles and impaired the 
calcium release needed for normal egg shell formation.
    On March 11, 1967 (32 FR 4001), the Secretary of the Interior 
listed bald eagles south of the 40th parallel (latitudinal line running 
roughly from northern California to New Jersey) as endangered under the 
Endangered Species Preservation Act of 1966 (16 U.S.C. 668aa-668cc). On 
December 31, 1972, DDT was banned from use in the United States by the 
Environmental Protection Agency.
    Nationwide bald eagle surveys conducted in 1973 and 1974 revealed 
the declining trend of bald eagle population numbers throughout the 
lower 48 States. We responded by listing the bald eagle throughout the 
lower 48 States as endangered except in Michigan, Minnesota, Wisconsin, 
Washington, and Oregon, where the bald eagle was designated as 
threatened (43 FR 6233, February 14, 1978). Nesting populations of bald 
eagles have more recently been increasing throughout the United States. 
Data from surveys conducted between 1963 and 1998 show that known 
active nest sites in the lower 48 States have grown from 417 to over 
5,748 occupied BAs (USFWS 1995, p. 36001; USFWS 1999, p. 36457). Today, 
the Service estimates the population in the lower 48 states to be at 
approximately 7,066 breeding pairs (USFWS 2006, p. 8239).
    The 1982 recovery plan for the Southwestern Recovery Region states 
that when the total reproduction for the eagle population within the 
Southwestern Recovery Region as a whole has effectively doubled to 10-
12 young per year over a 5-year period, and the population range has 
expanded to include one or more river drainages in addition to the Salt 
and Verde River Systems, the southwestern bald eagle should be 
reclassified to threatened. The 1982 recovery plan indicated that 
Arizona was the only State in the recovery region containing nesting 
bald eagles, with 42 unverified historical nesting territories in the 
Salt and Verde River systems, and one occupied territory along the 
Colorado River. As discussed in the February 16, 2006, Federal Register 
notice reopening the comment period on the proposed rule to delist the 
bald eagle through its range (71 FR 8238), the downlisting goal 
established in the recovery plan for the southwestern bald eagle has 
been exceeded. Further, on July 12, 1995, we reclassified the bald 
eagle from endangered to threatened in the lower 48 States (60 FR 
    The number of known BAs has increased from a low of 3 in 1971, to a 
high of 50 in 2006, while the number of occupied BAs increased from a 
low of 3 in 1971, to a high of 43 in 2006. The number of young hatched 
increased from a low of 0 in 1972, to a high of 55 in 2006 (AGFD 2006, 
pp. 48-49; AGFD unpubl. data 2006). Productivity has also changed. 
Between 1975 and 1984, average productivity was 0.95 young per occupied 
BA. Between 1987 and 2005, average productivity was 0.78 young per 
occupied BA. These data take into account productivity for BAs 
throughout the Southwest, and they are not restricted to the Sonoran 
Desert population of bald eagles evaluated under the petition.
    While the number of BAs has increased, there was no expectation 
that these BAs would demonstrate a corresponding increase in 
reproductive performance. In part, this is because early monitoring 
detected BAs with the highest quality habitat that were easily 
discovered. Following an intensive survey effort, we now know of more 
BAs, but habitat conditions within them ranges from poor to excellent. 
As a result, we are now tracking productivity in BAs with a variety of 
habitat conditions, rather than tracking productivity in only those BAs 
that were easily detected and were in prime habitat. The result of 
having more thorough, representative data from more BAs in a variety of 
habitat types is that we show fewer ``boom and bust'' years. 
Productivity data between 1987 and 2005 indicates a more stabilized 
performance. For example, in 1971, with only three known BAs, 
productivity was 1.33. In 1972, with the same number of known BAs, 
productivity was 0.0. In 1973, productivity was at 1.5. By comparison, 
with more BAs known, productivity fluctations now typically vary by 
only 0.20 to 0.30 (AGFD 2006, pp. 48-49; AGFD unpubl. data 2006).
    AGFD (2006c, p. 5) additionally notes that the change in 
productivity could be due to a difference in monitoring protocols. More 
importantly, they note that an average productivity rate of 0.78 young/
occupied breeding area is consistent with the range of many other areas 
in the species range with larger bald eagle populations, including 
Minnesota, British Columbia, Interior Alaska, and Washington.
    For the Sonoran Desert population of bald eagles (i.e., excluding 
those BAs not considered within the area of analysis under this 
action), the number of occupied BAs increased from a low of 3 in 1971 
to a high of 36 in 2004. Productivity for only those BAs within the 
Sonoran Desert population is that same as that for the southwestern 
population up until 1994, when BAs outside of the Sonoran Desert 
population were discovered. From 1994 forward, productivity within the 
Sonoran Desert population has ranged between 0.62 and 1.06, reaching a 
high in 2004. Productivity remained high at 1.01 young per occupied BA 
for 2005 (AGFD 2004a, p. 15; AGFD 2004, p. 6; AGFD 2005, p. 7; AGFD 
2006, Table 7, pp. 48-50). The average annual productivity for this 
time period is at 0.78, which corresponds to that for the overall 
southwestern population.

Previous Federal Actions

    On March 11, 1967 (32 FR 4001), bald eagles south of 40 degrees 
north latitude were federally listed as an endangered species. Bald 
eagles north of this line were not listed at that time because those 
populations had not experienced the same threats and population 
declines as of 1967. On February 14, 1978, we listed the bald eagle as 
endangered in 43 States, and threatened in 5 others (43 FR 6233). Bald 
eagles were not listed in Alaska, and are not found in Hawaii. On July 
12, 1995, we reclassified the bald eagle from endangered to threatened 
in the lower 48 States (60 FR 36000). The bald eagle remained 
classified as threatened in Michigan, Minnesota, Wisconsin, Oregon, and 
Washington, as originally listed.
    On July 6, 1999, we proposed to remove the bald eagle from the List 
of Endangered and Threatened Wildlife in the lower 48 States, including 
the Southwest Recovery Region (64 FR 36454). The original comment 
period was open for 90 days, until October 5, 1999. We reopened the 
comment period on that proposal on February 16, 2006 (71 FR 8238), for 
an additional 90 days, until May 17, 2006, and we extended the comment 
period on May 16, 2006 (71 FR 28369), for another 30 days, until June 
19, 2006.

Distinct Vertebrate Population Segment

    We consider a species for listing under the Act if available 
information indicates such an action might be warranted. ``Species'' is 
defined by the Act as including any species or subspecies of fish and 
wildlife or plants,

[[Page 51552]]

and any distinct vertebrate population segment of fish or wildlife that 
interbreeds when mature (16 U.S.C. 1532(16)). We, along with the 
National Marine Fisheries Service (now the National Oceanic and 
Atmospheric Administration--Fisheries), developed the Policy Regarding 
the Recognition of Distinct Vertebrate Population Segments (DPS policy) 
(61 FR 4722, February 7, 1996), to help us in determining what 
constitutes a DPS. The policy identifies three elements that are to be 
considered in a decision regarding the status of a possible distinct 
population segment (DPS). These elements include (1) the discreteness 
of the population in relation to the remainder of the species to which 
it belongs; (2) the significance of the population segment to the 
species to which it belongs; and (3) the population segment's 
conservation status in relation to the Act's standards for listing. Our 
policy further recognizes it may be appropriate to assign different 
classifications (i.e., threatened or endangered) to different DPSs of 
the same vertebrate taxon (61 FR 4721; February 7, 1996).
    In the Service's final rule reclassifying the bald eagle from 
endangered to threatened (July 12, 1995, 60 FR 36000), we determined 
that eagles in the Southwestern Recovery Region were part of the same 
bald eagle population as that of the remaining lower 48 States, and we 
determined it was appropriate to include it in the reclassification. 
However, the petition requests action with respect to an area (i.e., 
Sonoran Desert) that differs from the area that was analyzed in the 
reclassification rule (i.e., Southwestern Recovery Region),and provides 
new information not considered in 1995.


    The DPS policy states that a population segment of a vertebrate 
species may be considered discrete if it satisfies either one of the 
following two conditions: It must be markedly separated from other 
populations of the same taxon as a consequence of physical, 
physiological, ecological, or behavioral factors, or it must be 
delimited by international boundaries within which significant 
differences in control of exploitation, management or habitat 
conservation status or regulatory mechanisms exist that are significant 
in light of section 4(a)(1)(D) of the Act. Our evaluation of 
discreteness under the DPS policy, based on information provided in the 
petition and available in our files, is presented below.

Discreteness Criteria 1. The Population Segment is Markedly Separated 
From Other Populations of the Same Taxon as a Consequence of Physical, 
Physiological, Ecological, or Behavioral Factors. Quantitative Measures 
of Genetic or Morphological Discontinuity May Provide Evidence of This 

Ecological Factors
    The petition notes the geographic region occupied by Sonoran Desert 
bald eagles is much drier and hotter than that of any other bald eagle 
population, and represents a significant departure from the habitat 
selected by bald eagles in the rest of North America. The petition 
concludes that, in order to adapt to high summer temperatures and to 
time breeding cycles to the accessibility and spawn of native fish 
(primarily suckers), Sonoran Desert bald eagles breed earlier, nest 
earlier, and fledge their young sooner than bald eagles elsewhere (AGFD 
1999a, 2000; Gerrard and Bortolotti 1988; Hunt et al. 1992; Stalmaster 
1987; USFWS 2003b). In addition, the petition notes that, unlike bald 
eagles elsewhere in North America, Sonoran Desert bald eagles use cliff 
nest sites and that 53 of 111 known nests, or 48 percent, are on cliffs 
or pinnacles. They further note the only other place this occurs is in 
the Aleutian Islands (Hunt et al. 1992).
Response to the Petition
    The information provided in the petition on behavioral adaptations 
to the Sonoran Desert is, in part, accurate. While it is true that 
Sonoran Desert bald eagles initiate nesting earlier than eagles in some 
parts of the country, Stalmaster (1987, p. 63) notes bald eagles in 
Florida initiate breeding activities in October, even earlier than 
Arizona bald eagles. Florida bald eagles also lay eggs earlier 
(Stalmaster 1987, p. 63; Gerrard and Bortolotti 1988 p. 76). 
Accordingly, Florida bald eagles hatch and fledge earlier than those in 
Arizona. Stalmaster (1987, p.63) concludes timing of various breeding 
events is tied to latitude of the nesting area, with eagles at more 
northern latitudes breeding at later dates.
    With respect to cliff nesting, the information presented on the use 
of cliff nests is accurate. However, this is not necessarily a unique 
trait of Sonoran Desert bald eagles. Gerrard and Bortolotti (1988, p. 
41) note bald eagles in other areas may nest on cliffs if suitable 
trees are not available. Stalmaster (1987) noted exceptions to tree 
nests as well, but indicated that, while eagles in other areas may 
rarely use cliffs or other surfaces, this is an exception, whereas in 
Arizona, cliff nesting is common. In addition, bald eagles are known to 
nest on cliffs on the Channel Islands off California (Montrose 
Settlements Restoration Program 2005).
Behavioral Factors
    The petition provides information alleging that the Sonoran Desert 
bald eagles are reproductively isolated. Specifically, the petition 
contends that 352 out of 353 individuals (99.997 percent) objectively 
identified while participating in breeding activity in this population 
came from within the Sonoran Desert bald eagle population. 
Additionally, the petition notes that, since 1977, biologists in 
Arizona have banded 256 nestlings with only one individual identified 
as having emigrated. According to the petition, this indicates that 
99.6 percent of individuals born into the Sonoran Desert remain in the 
desert (AGFD 1999a, 2000). The petition states that, to date, evidence 
from the banding and identification of breeding adults supports the 
hypothesis that the Sonoran Desert bald eagle breeding population is 
not supported or maintained by immigration from other states or 
regions. They quote AGFD (1999a, 2000):

    ``[B]ecause adults return to the vicinity of their natal area to 
breed, the large distance between small breeding populations in the 
Southwest decreases the chance for movement between neighboring 
populations. Probably most convincing are the results from banding 
256 nestlings over 20 years and identifying 372 breeding adults over 
8 years. Only one individual from out-of-state entered the breeding 
population and only one left. Additionally, the proportion of 
breeding adults with color bands had steadily increased, while the 
presence of unmarked Bald Eagles has decreased. Thus, continued 
attention to the survivorship of all Arizona Bald Eagles is vital to 
the maintenance of our breeding population. We can not depend on 
immigration to Arizona from nearby states to make up for poor 
management in Arizona * * *''

    The petition claims the AGFD (1994b) warned that repopulation of 
the Sonoran Desert bald eagle population following a population crash 
would be highly unlikely, and quote the AGFD (1994b) as follows:

    ``Because Arizona continues to possess nearly the entire 
breeding population within the Southwestern Region, concerns remain 
over retaining the genetic integrity of this population * * * Should 
a population crash occur in Arizona, the pool of eagles to 
repopulate the Southwest could be left to the few pairs in the 
neighboring states or Mexico. However, at this time, there is no 
documentation of eagles from these neighboring Southwestern states 
breeding in Arizona or vice versa.''

[[Page 51553]]

    The petition further states that natal site fidelity is common for 
bald eagles, noting that, in a study of nine bald eagle populations 
including thousands of banded birds, only two nestlings were found to 
have bred in other areas. One of these birds moved 331 kilometers (205 
miles) north from its natal site in the Greater Yellowstone Ecosystem 
(Harmata in litt.) while the other traveled 418 kilometers (260 miles) 
south from its natal site near Charleston, South Carolina (T. Murphy, 
pers. comm., Wood in litt.). They conclude that the tendency for banded 
nestlings to breed within their natal populations is well known (Hunt 
et al. 1992).
Response to the Petition
    The information in the petition appears to be accurate and 
reliable; however, it should be noted the only individual cited as 
entering the breeding population from out-of-state refers to a bald 
eagle from Texas (AGFD 2006, p. 27) that currently occupies the Luna 
BA, which is not part of the Sonoran Desert bald eagle population. As a 
result, the appropriate conclusion is all birds objectively identified 
while participating in breeding activity in the Sonoran Desert bald 
eagle population came from within the population. It should also be 
noted that sub-adult bald eagles do migrate and return annually. As 
noted above, about 45 days after leaving the nest, young southwestern 
bald eagles migrate to Canada, northern California, Idaho, Montana, 
North and South Dakota, Oregon, Washington, and Wyoming (Hunt et al. 
1992, p. A-104--A-114), returning to Arizona in the fall of the same 
year. They are known to repeat this behavior for a minimum of 2 years 
(Hunt et al. 1992a-112; p. A-122--A-123). Resident adult bald eagles 
often stay in their BAs year-round, although local short-term 
migrations are common (AGFD 1999, p. 6).
    We agree with the petitioners that, should the Sonoran Desert bald 
eagle population experience a rapid decline, there are few eagles in 
neighboring southwestern states or Mexico which could serve as a source 
population for the Sonoran Desert bald eagle population. Finally, we 
find the information from Harmata et al. (1999, p. 788) and Hunt et al. 
(1992, p. A-144) supports the discussion on the natal origins of 
breeding adults, and the probability that adult bald eagle will not 
immigrate to the Sonoran Desert bald eagle population from surrounding 
southwestern states or farther.
Evidence of Genetic Discontinuity
    With respect to genetic isolation, the petition found that the 
current understanding of genetics does not refute the discrete and 
isolated nature of the desert nesting bald eagle. The petition notes a 
review of all information regarding genetic analysis of the 
southwestern desert nesting bald eagle reveals consistent uncertainty, 
and concludes current genetic data support no definitive conclusions 
concerning isolation or lack of isolation (CBD 2004e; Hunt et al. 1992; 
SWCBD 1999). The petition states that, while no definitive conclusions 
are supported by the limited genetic data, this is not required under 
the current DPS policy. Specifically, the petition quotes from the 

    ``Thus, evidence of genetic distinctness or of the presence of 
genetically determined traits may be important in recognizing some 
DPS's, but the draft policy was not intended to always specifically 
require this kind of evidence in order for a DPS to be recognized * 
* *''

    Similarly, the petition notes absolute reproductive isolation is 
not required under the policy, which states:

    ``The Services do not consider it appropriate to require 
absolute reproductive isolation as a prerequisite to recognizing a 
distinct population segment. This would be an impracticably 
stringent standard, and one that would not be satisfied even by some 
recognized species that are known to sustain a low frequency of 
interbreeding with related species * * *''
Response to the Petition
    The information presented within the petition on completed genetic 
studies for bald eagles appears accurate and reliable. Hunt et al. 
(1992, pp. E-96 to E-110) contains the genetic work completed to date 
on the southwestern bald eagle population. Vyse (1992, p. E-100, E-101) 
notes the data are inconclusive, as evidenced by such statements as 
``These findings must be assumed to be preliminary (and treated with 
due caution), because of a lack of information concerning sampling 
procedures. The results we have obtained could easily be explained by 
sampling procedures''; and ``At present these data (HinfI/M-13) are too 
incomplete to be considered further.'' In addition, Zegers et al. 
(1992, p. E-106 to E-109) notes that ``Question 4 * * * is difficult to 
answer with precision because of the different sample sizes between 
1985 and 1990. * * * [T]his difference is possibly an artifact of the 
many fewer samples in 1985''; ``six loci may not be enough to give a 
reliable estimate of the true genetic distance'; and ``We feel caution 
should be exercised when interpreting these results due to the low 
numbers of individuals sampled from most states but especially because 
of the few loci examined.''
Evidence of Morphological Discontinuity
    The term ``morphological discontinuity'' refers to some difference 
in physical characteristics that may exist between two groups. The 
petition contends that quantitative measures of the physical 
differences between Sonoran Desert bald eagles and bald eagles 
elsewhere offers evidence of morphological discontinuity. The petition 
cites quantitative measures of physical difference, stating that 
average weights of male bald eagles are 3.3 kilograms (kg) (7.3 pounds 
(lbs.)) in Arizona, 4.1 kg (9.0 lbs.) in California, and 4.7 kg (10.4 
lbs.) in Alaska. Similarly, average weight for females is 4.5 kg (9.9 
lbs.) in Arizona, 5.1 kg (11.2 lbs.) in California, and 5.8 kg (12.8 
lbs.) in Alaska (Hunt et al. 1992).
Response to the Petition
    The information provided on size differences appears to be accurate 
and reliable, as found in Hunt et al. (1992, p. A-159). Stalmaster 
(1987, pp. 16-17) notes southern eagles are much smaller and lighter 
than their northern counterparts. This is consistent with Bergmann's 
Rule, which holds that animal size increases with increasing latitude. 
Gerrard and Bortolotti (1988, p. 14) note Florida birds are the 
smallest, with a gradation of small to large from south to north. The 
importance of this morphological difference and its potential isolating 
effects are discussed by Hunt et al. (1992, p. A-165), who notes 
morphological differences such as small size may be an adaptation 
related to desert conditions, noting a decision to release birds into 
Arizona from elsewhere should be considered only as a last resort, as 
the introduction of foreign genes into the Sonoran Desert population 
might disrupt coadapted gene complexes specific to the desert 

Discreteness Criteria 2. It is Delimited by International Government 
Boundaries Within Which Differences in Control of Exploitation, 
Management of Habitat, Conservation Status, or Regulatory Mechanisms 
Exist That are Significant in Light of Section 4(a)(1)(D) of the Act

    No specific information was identified in the petition for this 
category. Therefore we will not address this category in our analysis 
of discreteness.
    We have reviewed the information presented in the petition, and 

[[Page 51554]]

evaluated the information in accordance with 50 CFR 424.14(b). On the 
basis of our review, we find available genetic studies on bald eagles 
are dated, the sample size was small, and researchers conducting the 
studies found the results to be inconclusive. We therefore believe that 
the best available genetic information is inconclusive with regard to 
the discreteness of the Sonoran Desert bald eagle population. However, 
we believe the petition presents substantial information on the Sonoran 
Desert bald eagles with respect to size. However, size in birds is 
known to be a clinal function of latitude and does not necessarily 
indicate discreteness. We believe the petition provides substantial 
information on natal site fidelity in breeding birds and the limited 
number of other eagles in neighboring southwestern states or Mexico. 
Finally, we believe the data indicating that 20 years of monitoring 
have resulted in the determination that no eagles have immigrated to 
and only one eagle has emigrated from the Sonoran Desert bald eagle 
population is substantial. We, therefore, conclude that the petition 
contains substantial information with respect to the discreteness 
requirements of the DPS policy to warrant considering the Sonoran 
Desert bald eagle population as discrete from other bald eagle 
    If we determine that a population segment is discrete under one of 
the above conditions, we must then consider its biological and 
ecological significance to the taxon to which it belongs, within the 
context that the Service's authority to list DPSs be used ``sparingly'' 
while encouraging the conservation of genetic diversity (61 FR 4722; 
February 7, 1996). This consideration may include, but is not limited 
to the following: (1) Evidence of the persistence of the population 
segment in an ecological setting that is unique for the taxon; (2) 
evidence that loss of the population segment would result in a 
significant gap in the range of the taxon; (3) evidence that the 
population segment represents the only surviving natural occurrence of 

a taxon that may be more abundant elsewhere as an introduced population 
outside of its historic range; and (4) evidence that the discrete 
population segment differs markedly from other populations of the 
species in its genetic characteristics.

Significance Criteria 1. Persistence of the Population Segment in an 
Ecological Setting That Is Unusual or Unique for the Taxon

Information Provided in the Petition
    The petition contends that the Sonoran Desert bald eagle persists 
in the unique ecological setting of the Sonoran life zones of the 
desert Southwest (AGFD 1999a, 2000; Hunt et al. 1992; USFWS 2002a, 
2003b). With the exception of a single 8,000 foot (2,438 meter) 
elevation nest (Luna BA), the petition states that all known Arizona 
BAs are located in the Sonoran Desert in the central part of the State 
in Upper and Lower Sonoran Desert habitats from elevations of 1,080 
feet (330 meters) to 5,640 feet (1,720 meters), and are closely 
associated with the Salt, Verde, and Gila river drainage waters (Beatty 
and Driscoll 1994, 1996a; Beatty et al. 1995a, 1995b, 1998; Driscoll 
and Beatty 1994; Driscoll et al. 1992; Hunt et al. 1992). The petition 
further identifies several Arizona tree species native to the desert 
Southwest as representative vegetation for these areas (Brown 1994).
Response to the Petition
    The breeding range of the bald eagle is associated with aquatic 
habitats (coastal areas, river, lakes, and reservoirs) with forested 
shorelines or cliffs in North America (Buehler 2000). The ecological 
setting in which the bald eagle persists in the Sonoran Desert may at 
first seem unusual for the species. However, despite the desert 
setting, bald eagles of the Sonoran Desert are consistently associated 
with preferred bald eagle habitat, the riparian ecosystem. The petition 
clearly states that the Sonoran Desert nests are closely associated 
with the Salt, Verde, and Gila river drainage waters and cites Brown 
(1994) when describing the riparian vegetation of these areas. As with 
all populations of bald eagles throughout the lower 48 States, suitable 
riparian habitat, or other comparable aquatic habitat, is an essential 
prerequisite to successful eagle reproduction in the desert Southwest 
(USFWS 1982). Riparian ecosystems occupied by nesting bald eagles in 
the Sonoran life zones of the desert Southwest, therefore, do not 
constitute a unique setting for the species. The persistence of the 
bald eagle in this setting likely represents an example of a species 
occupying the edge of its range of suitable habitats. Therefore, we 
conclude that the petition does not present substantial evidence that 
the population is persisting in an ecological setting that is unique 
for the taxon.

Significance Criteria 2. Loss of the Population Segment Would Result in 
a Significant Gap in the Range of the Taxon

Information Provided in the Petition
    The petition contends that for more than twenty years, the Service 
has recognized the fact that the Southwest represents a ``significant 
portion of the bald eagle range'' and further states that it follows 
logically then that the loss of the [Sonoran] Desert nesting population 
would result in a significant gap in the range of the bald eagle (Hunt 
et al. 1992; USFWS 1982, 1994a, 1995, 2001a). The petition claims that 
bald eagles in the Southwestern United States have been considered as a 
distinct population for the purposes of consultation and recovery 
efforts under the Act (USFWS 2003b).
    The petition further contends that several authors have speculated 
about the consequences of this population's loss (AGFD 1994b; Hunt et 
al. 1992), and the petitioners can find no credible evidence that bald 
eagles elsewhere possess the ability to adapt to the unique and hostile 
environmental habitat in which the [Sonoran] Desert nesting population 
has evolved. Specifically the petition quotes Hunt et al. (1992):

    ``[W]ere the [Southwestern Desert Nesting Bald Eagle] population 
extirpated, there is no firm reason to believe that bald eagles 
released into Arizona from elsewhere would posses [sic] the 
adaptations required to increase their numbers.''

    The petition further quotes correspondence from the Arizona Game 
and Fish Department to the Service (1994b):

    ``Because Arizona continues to possess nearly the entire 
breeding population within the Southwestern Region, concerns remain 
over retaining the genetic integrity of this population. * * * 
Should a population crash occur in Arizona, the pool of eagles to 
repopulate the Southwest could be left to the few pairs in the 
neighboring states or Mexico. However, at this time, there is no 
documentation of eagles from these neighboring Southwestern States 
breeding in Arizona or vice versa.''
Response to the Petition
    The petition cites several Service publications (1982, 1994a, 1995, 
2001a) in addition to a report prepared by Hunt et al. (1992) when 
making this claim, but does not make specific reference to instances in 
which the Service has ``recognized the fact that the Southwest 
represents a significant portion of the Bald Eagle range.'' Therefore, 
for this analysis we will assume that the petition is referring to the 
fact that the

[[Page 51555]]

Service has continued to identify the Southwest population of the bald 
eagle as one of five recovery populations in the lower 48 States for 
more than twenty years (Hunt et al. 1992; USFWS 1982, 1994a, 1995, 
    In establishing a recovery program for the species in the mid-
1970's, the Service divided the bald eagles of the lower 48 States into 
five recovery populations, based on geographic location, termed 
Recovery Regions. This was as a result of the wide distribution of the 
bald eagle in the lower 48 States. Recovery plans were prepared for the 
five Recovery Regions, including the Southwest Recovery Region (USFWS 
1982), by separate recovery teams composed of species experts in each 
geographic area. The Service views the establishment of recovery 
regions as a management tool allowing for effective regional 
coordination and planning among State and Federal conservation agencies 
and species experts. The existence of a recovery region does not, in 
itself, imply significance under the DPS policy (USFWS and NMFS 1996), 
as the petitioner claims, and therefore the Southwestern Recovery 
Region is not a DPS for the purposes of recovery.
    In the 1994 proposed rule to reclassify the bald eagle from 
endangered to threatened (59 FR 35584; July 12, 1994), the Service 
determined that current information indicates the Southwestern 
population is at risk and remains in danger of extinction due to 
excessively low survival rates and the need for intensive management, 
particularly at nest sites. This decision was based on the 
understanding that the population was isolated and thus subject to the 
genetic, demographic, and environmental threats known to be associated 
with small populations. Data provided in the Hunt et al. (1992) 
publication indicated there had been no immigration to the Southwestern 
population of bald eagles. At that time the Service recognized the 
Southwestern Recovery Region as a DPS based on evidence that it 
appeared to be reproductively isolated (59 FR 35584; July 12, 1994). 
However, in the 1995 final rule to reclassify bald eagles from 
endangered to threatened, the Service affirmed that the Southwestern 
Recovery Region of the bald eagle is not a DPS but instead part of the 
same bald eagle population as that of the remaining lower 48 States 
(USFWS 1995). This determination was based on evidence of immigration 
into the population (USFWS 1995), inter-population movements (Mabie et 
al. 1994), and the then existing genetic data, which did not support 
the Service's previous assertion that the bald eagles of the 
Southwestern Recovery Region are reproductively isolated (Hunt et al. 
    On July 6, 1996, the Service and the National Marine Fisheries 
Service jointly published a policy that clarifies the Agencies' 
interpretation of the phrase ``distinct population segment of any 
species of vertebrate fish or wildlife'' for the purposes of listing, 
delisting, and reclassifying species under the Act (USFWS and NMFS 
1996). The policy identifies three elements that are to be considered 
in a decision regarding the status of a possible distinct population 
segment (DPS). These elements include (1) the discreteness of the 
population segment in relation to the remainder of the species to which 
it belongs; (2) the significance of the population segment to the 
species to which it belongs; and (3) the population segment's 
conservation status in relation to the Act's standards for listing 
(USFWS and NMFS 1996).
    Subsequent to publication of the DPS policy, the Service published 
a proposed rule to remove the bald eagle in the lower 48 States from 
the list of endangered and threatened wildlife (USFWS 1999). On 
February 16, 2006 the Service reopened the comment period for the 
proposed rule (USFWS 2006). In both of these publications the Service 
recognized a single listed population of bald eagles throughout the 
lower 48 States as had been done in the earlier 1995 final rule (USFWS 
1995), although a formal analysis consistent with the 1996 DPS policy 
had not been completed for the Southwestern Recovery Region (USFWS 
1999, 2006).
    The petition is correct in that early biological opinions, as part 
of consultations with Federal action agencies under section 7 of the 
Act, finalized by the Arizona Ecological Services Office referred to 
the Southwestern population as a DPS. However, in the 1995 final rule 
to reclassify bald eagles from endangered to threatened (USFWS 1995), 
the Service affirmed that the Southwestern population of the bald eagle 
is not a DPS. Some biological opinions dated after the final rule note 
that the Southwestern population of the bald eagle was previously 
considered a DPS, but no longer is considered as such. In the February 
16, 2006 reopening of the comment period for the proposed rule to 
delist the bald eagle, the Service further explains that when preparing 
biological opinions under section 7 of the Act the potential effects to 
the Southwestern or any of the other four recovery regions of the bald 
eagle are considered in terms of whether they appreciably reduce the 
likelihood of both survival and recovery of the bald eagle throughout 
the lower 48 States, not solely for the geographic area in which the 
impacts may occur (USFWS 2006). Therefore, the bald eagles in the 
Southwestern United States are not considered as a distinct population 
for the purposes of consultation under the Act. Further, the petition 
under consideration in this finding requests action with respect to a 
geographic area (i.e., Sonoran Desert) that differs from the area that 
was analyzed in the Service's reclassification rule (i.e., Southwestern 
Recovery Region) (USFWS 1995). In this context, claims regarding how 
the Service has referred to the Southwest Recovery Region are not 
relevant to the petitioned action.
    Finally, the bald eagle ranges throughout much of North America, 
nesting on both coasts from Florida to Baja California in the south, 
and from Labrador to the western Aleutian Islands, Alaska in the north 
(Gerrard and Bartolotti 1988). While the statements of two authors who 
have ``speculated'' about the consequences of the Sonoran Desert 
population's loss are accurately quoted, these statements do not 
specifically address how the loss of the Sonoran Desert bald eagle 
population would constitute a significant gap in the range of the 
species. Furthermore, the petitioner provides no supporting evidence to 
substantiate the authors' speculations.
    We conclude that the bald eagles in the Southwestern United States 
are not considered as a distinct population for the purposes of 
consultation or recovery. Furthermore, the petition does no provide 
substantial information to support the claim that loss of the Sonoran 
Desert bald eagle population would result in a significant gap in the 
range of the species.

Significance Criteria 3. The Population Segment Represents the Only 
Surviving Natural Occurrence of a Taxon That May Be More Abundant 
Elsewhere as an Introduced Population Outside Its Historical Range

    The petition does not address this factor. The bald eagle occurs 
naturally throughout the contiguous 48 States, Alaska, Canada and 
Mexico (Buehler 2000). As such, the Sonoran Desert population does not 
represent the only surviving natural occurrence of the taxon.

[[Page 51556]]

Significance Criteria 4. The Discrete Population Segment Differs 
Markedly From Other Populations of the Species in its Genetic 

Information Provided in the Petition
    The petition contends that review of all information regarding 
genetic analysis of the Southwestern desert nesting bald eagle reveals 
consistent uncertainty and the current understanding of genetics does 
not refute the discrete and isolated nature of the desert nesting bald 
eagle (CBD 2004e; Hunt et al. 1992; SWCBD 1999). The petition 
specifically quotes excerpts from Hunt et al. (1992), which discuss 
genetics study methods, results, and conclusions.
Response to the Petition
    We have addressed the genetic evidence provided by the petitioner 
in the analysis of discreteness above. Consistent with that analysis we 
have determined that the best available genetic information is 
inconclusive with regard to significance. We conclude that the petition 
does not present substantial information that the population differs 
markedly from other populations of the species in its genetic 
characteristics. Further, the petition does not present nor are we 
aware of any other factors that would lead us to believe that the 
Sonoran Desert population of the bald eagle differs markedly from the 
taxon as a whole.
    We have reviewed the information presented in the petition, and 
have evaluated the information in accordance with 50 CFR 424.14(b). On 
the basis of our review, we find that the petition does not present 
substantial scientific or commercial information to indicate that the 
Sonoran Desert bald eagle constitutes a valid DPS. Although the 
population is discrete, the petition does not present substantial 
scientific information that the Sonoran Desert bald eagle may be 
significant in relation to the remainder of the taxon. Therefore, we 
conclude that the Sonoran Desert population is not a listable entity 
pursuant to section 3(15) of the Act. However, recognizing the volume 
of information provided in the petition, and the national importance of 
the bald eagle, we have also conducted a threats analysis.

Threats Analysis

    Pursuant to section 4 of the Act, we may list a species, 
subspecies, or DPS of vertebrate taxa on the basis of any of the 
following five factors: (A) Present or threatened destruction, 
modification, or curtailment of habitat or range; (B) overutilization 
for commercial, recreational, scientific, or educational purposes; (C) 
disease or predation; (D) inadequacy of existing regulatory mechanisms; 
or (E) other natural or manmade factors affecting its continued 
existence. The Act identifies the five factors to be considered, either 
singly or in combination, to determine whether a species may be 
threatened or endangered. Our evaluation of these threats in terms of 
the petitioned action to reclassify the Sonoran Desert bald eagle from 
threatened to endangered, based on information provided in the petition 
and available in our files, is presented below. Throughout this finding 
we refer to the Sonoran Desert population of the bald eagle, because 
that is the petitioned entity; however, as noted above, this reference 
does not imply that we have determined, under to our DPS policy, that 
this population is a listable entity. Furthermore, although we have 
proposed the bald eagle in the lower 48 States for delisting (71 FR 
8238, February 16, 2006), our petition finding does not address the 
proposed delisting or conditions that may occur if the delisting is 

A. Present or Threatened Destruction, Modification, or Curtailment of 
the Species' Habitat or Range

Development, Recreation, and Water Use
    The petition notes that the Southwest has already lost more than 90 
percent of its historical riparian communities (AGFD 1993; Krueper 
1993; Lofgren et al. 1990), and that the loss of riparian communities 
is continuing due to increasing development, dewatering via groundwater 
pumping and diversions, destructive cattle grazing, and lack of 
vegetation-rejuvenating floods. The petition contends that the Sonoran 
Desert bald eagle population faces imminent and accelerating loss of 
increasing amounts of habitat vital to its long-term survival. 
Specifically, the petition notes that most of the BAs are located along 
the Salt and Verde rivers near the Phoenix metropolitan area and the 
towns of Cottonwood and Camp Verde in Yavapai County, where habitat 
loss is occurring due to the increasing human population in central 
Arizona. The petition notes that the human population in Maricopa 
County is expected to double to more than six million people over the 
next 30 years (Arizona Republic 1998). Growth in Cottonwood, on the 
Verde River, is projected to increase by 148 percent and in Camp Verde 
by 158 percent between 1994 and 2040 (Arizona Department of Economic 
Security 1994). The petition notes that increases in human populations 
of this magnitude will result in increased housing development, water 
demands, and recreational use.
    The petitioners contend that development will affect the 
suitability of many BAs due to their proximity to areas with large 
human populations and projected population growth rates. The petition 
notes that increased recreational use, development, and water use will 
follow increasing population sizes, and cites examples of past 
consultations, conducted by the Service under section 7 of the Act, 
addressing these issues.
    The petition cites recent examples of recreational impacts to 
Sonoran Desert bald eagle BAs, including river tubing on the Salt 
River, which increases the human presence near the Blue Point BA, as 
well as campground development at Roosevelt Lake, which could affect 
the Sheep and Tonto BAs. The petition cites, as development examples, a 
360-home development and golf course within 1.0 mile (1.6 kilometers 
(km)) of the Box Bar BA; the development of lakeside resorts at Lake 
Pleasant near the Pleasant BA; and continued housing, road, and 
business developments along lower Tonto Creek near the Sheep and Tonto 
BAs (AGFD 1999a, 2000).
    The petition notes that dewatering of the middle portion of the 
Verde River is accelerating so that flows have at times been reduced to 
12 cubic feet per second (0.3 cubic meters per second) in summer months 
near the Camp Verde White Bridge gauge (Verde Natural Resources 
Conservation District 1999). The petition contends that this dewatering 
is resulting in a reduction in base flows, and increased populations in 
Cottonwood and Camp Verde are leading to increased groundwater pumping. 
The petition indicates that groundwater pumping in Arizona has 
repeatedly been demonstrated to result in a depletion of surface flows, 
degradation and loss of riparian communities, and adverse impacts and 
local extirpation of aquatic flora and fauna (ADWR 1994; Ewing et al. 
1994; Glennon 1995; Glennon and Maddock 1994; Hendrickson and Minckley 
1984; McGavock 1996, Miller 1961; Owen-Joyce and bell 1983, Stromberg 
1993; Tellman et al. 1997).
    The petition notes that increased water demand is expected to have 
adverse effects on flows within rivers and resulting impacts on 
riparian communities. The petition further notes that 59.5 percent of 
all known desert bald eagle nests in Arizona have been in

[[Page 51557]]

riparian trees and snags (Driscoll 1999; E. Gardner, AGFD, pers. comm. 
2006). The petition notes that bald eagles at 11 BAs, including the Box 
Bar, Coolidge, Doka, Fort McDowell, Perkinsville, Pinto, 76, Sheep, 
Sycamore, Tonto, and Winkelman BAs, nest solely in riparian trees, and 
that the cottonwood trees used for nesting in these BAs have become 
overmature, are dying, and are not being replaced (AGFD 1991a, 2000). 
The petition contends that the loss of habitat in these BAs is 
particularly damaging to the future stability of the Sonoran Desert 
bald eagle population, as they have collectively contributed 22 percent 
of all recorded fledglings since 1971. The petition notes that the Fort 
McDowell BA has fledged 34 young, second only to the Blue Point BA, 
which has fledged 35 young (AGFD 1999a, 2000).
    Substantial detail is provided in the petition regarding specific 
development activities and resulting effects to Sonoran Desert bald 
eagle BAs. The petition notes that pressures associated with human 
population growth are increasing and will continue to do so as the 
human population increases.
Response to the Petition
    The information provided by the petitioner indicating that human 
population growth is expected to continue in areas in close proximity 
to or used by the Sonoran Desert bald eagle population appears accurate 
and reliable. Human population growth is an ongoing concern, and many 
of the bald eagle BAs in the Sonoran Desert population are within close 
proximity to this anticipated growth, including the Granite Reef, Orme, 
Rodeo, Sycamore, Doka, Fort McDowell, Box Bar, Needle Rock, and 
Bartlett BAs on the Verde River, and the Bull Dog, Blue Point, and 
Horse Mesa BAs on the Salt River, as well as the Pleasant BA at Lake 
Pleasant. As noted in the petition, recreation, development, and water 
use activities are ongoing and have increased since the bald eagle was 
listed. We have consulted on many of these actions through section 7 of 
the Act (including USFWS 1990b, 1996b, 1997b, 1998, 2001a and 2003b on 
water developments and USFWS 1993a for recreation, as cited in the 
petition). In addition, the AGFD's Projects Evaluation Program is 
available for Federal agencies or companies with a Federal nexus. This 
program can be used to evaluate the impacts of planned or future 
projects in areas where there may be a species of concern. The AGFD 
believes the program will help to ensure bald eagles and their habitat 
are considered and evaluated for possible effects from development 
projects (AGFD 2006, p. 14).
    Under section 7 of the Act, we have concluded to date that these 
actions would not jeopardize the continued existence of the bald eagle. 
The AGFD (2006c, p. 13) acknowledges that the need to accommodate human 
populations in proximity to a major metropolitan area like Phoenix will 
require ongoing management. However, they conclude that the species can 
be managed even under this scenario through the ``awareness, 
collaboration, flexibility, planning, and willingness of all wildlife, 
land, and recreation managers (AGFD 2006, p. 13).''
    We work cooperatively with the AGFD and Federal land managers to 
minimize the potential threats to bald eagle BAs in close proximity to 
the major human population growth areas in Arizona by establishing BA 
closures and monitoring the sites. In 2006, the Bartlett, Box Bar, 
Granite Reef, Orme, and Tonto BAs were monitored through the Arizona 
Bald Eagle Nestwatch Program. The program not only interacts with 
members of the public to provide education, but can intervene if 
individuals approach the nests too closely. Similarly, the Southwest 
Bald Eagle Management Committee, composed of State, Tribal, Federal, 
private, and military agencies, meets twice each year to address 
ongoing and new threats, funding for needed efforts, and general issues 
affecting the bald eagle.
    With the exception of the Pleasant and Bull Dog BAs, all of the BAs 
in close proximity to Phoenix successfully fledged young in 2006. One 
bird from the Bull Dog BA was successfully fledged following fostering 
in the Granite Reef BA. Orme, Rodeo, Doka, Fort McDowell, Box Bar, Blue 
Point, and Horse Mesa fledged one young each, while Sycamore, Needle 
Rock, and Bartlett produced two young each. Additionally, many of these 
BAs have successfully produced young for many years and, while nest 
failures do occur, their overall productivity remains high. For 
example, the Bartlett BA has fledged 28 young in 20 separate years 
between 1971 and 2002; the Blue Point BA has fledged 38 young in 18 
separate years between 1971 and 2002; and the Fort McDowell BA has 
fledged 41 young in 23 years between 1971 and 2002 (AGFD 2006, Table 7, 
pp. 48-50).
    The petitioners presented reliable and accurate data on the use of 
riparian areas for bald eagles, and on the potential loss of nest 
trees. In the 11 BAs referenced by the petitioners, existing trees have 
become over-mature, are dying, and are not being replaced (AGFD 2006, 
p. 12). The eagles in the Doka, Fort McDowell, Granite Reef, Rodeo, 76, 
and Sheep BAs currently nest in overmature live trees or snags with few 
available replacements. Trees may be lost to floodwaters, as at Fort 
McDowell in 1995 and 2005, or inundated due to reservoir level 
increases, as at the Pinto and Tonto BAs at Roosevelt Lake. In some 
cases, alternate trees are not available, as is the case at the Pinto 
BA. Housing communities and water-table reductions limit the available 
trees at the Tonto BA (AGFD 2006, p. 13).
    The AGFD (2006, p. 13) notes that the Fort McDowell Yavapai Nation 
(FMYN) and Salt River Pima Maricopa Indian Community (SRPMIC) have 
submitted proposals to the Arizona Water Protection Fund and Wetlands 
Protection Fund to plant riparian trees. The U.S. Bureau of Reclamation 
is analyzing ground-water levels in the Pinto BA for possible 
cottonwood pole plantings, and has helped to implement riparian 
restoration strategies within the Tonto Creek Riparian Unit. Salt River 
Project has purchased property for riparian enhancements on Roosevelt 
Lake. The exact impacts of increased human population growth and 
riparian losses, as well as the success of planting efforts in riparian 
areas, are speculative at this point. Through these management efforts, 
however, managing agencies can begin to minimize the factors impairing 
riparian regeneration.
    We agree with the petitioner that human population growth, 
particularly in Maricopa and Yavapai counties, will continue. While we 
can anticipate the types of impacts that might occur, the exact results 
of those impacts on occupancy and productivity are speculative at this 
point. We remain concerned for BAs such as Bartlett, Blue Point, and 
Fort McDowell, which have contributed much to the productivity of bald 
eagles in the Southwest. However, we find that productivity remains 
high despite the ongoing nature of this threat. While this is an 
ongoing threat, bald eagles have continued to survive and reproduce, as 
evidenced by the increased number of BAs throughout Arizona, and as 
evidenced by the productivity of the BAs outlined above. We therefore 
find that the petitioners did not provide substantial information to 
lead us to conclude that this threat has increased the likelihood of 
extinction for the Sonoran Desert bald eagle population.

[[Page 51558]]

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    No specific threats were identified in the petition for this 

C. Disease or Predation

    No specific threats were identified in the petition for this 

D. Inadequacy of Existing Regulatory Mechanisms

    The petition states that the Sonoran Desert population's survival 
is dependent, in good part, on heroic human support and management by 
the Arizona Bald Eagle Nestwatch Program (ABENWP). The petition notes 
that, over a 2-year period in 1996 and 1997, 13,999 human activities 
and 4,000 gunshots were recorded within 0.5 mile (0.8 km) of 13 nests. 
The petition contends that signs, education, and the threat of fines 
are insufficient deterrents to people, and that monitoring by 
nestwatchers has been, and continues to be, a crucial component of 
Sonoran Desert bald eagle management (AGFD 1999a, 2000).
    The petition additionally notes that, since 1983, 16 percent of all 
Sonoran Desert bald eagle fledglings have been saved by direct 
intervention of the ABENWP, with that intervention directly responsible 
for saving up to 60 percent of a single year's nestlings in some cases 
(USFWS 1992b). The petition notes that BAs such as Bartlett, Cliff, and 
76 would rarely produce young without the aid of nestwatchers (Hunt et 
al. 1992).
    The petition further notes that the ABENWP could become inadequate 
in the future as its funding is not secure. The funding comes from 
State grants such as AGFD's Heritage Fund, Federal agency contributions 
as mitigation for takings of the bald eagle under the Act, and 
volunteer funding. The petition finds that Heritage funding is insecure 
because it is derived from the State lottery, and income from the 
lottery has been decreasing. Additionally, the petition notes that 
there have been legislative attempts to divert lottery funds from 
protective wildlife activities. The petition contends that the proposed 
removal of the bald eagle from the Federal List of Endangered and 
Threatened Wildlife list will terminate mandatory Federal agency 
funding as well; the petition provides an example where the Bureau of 
Reclamation has asked us for clarification on terminating funding for 
one of its projects (USFWS 1996c). The petition provides additional 
examples of the tenuous nature of funding for the ABENWP (AGFD 1994a; 
Arizona Republic 2003a, 2004c, 2004f) and states that there are few 
binding consultations for any agency to commit funding to existing bald 
eagle programs; funding assistance by agencies is primarily based upon 
available funds and where the agencies choose to allocate them. The 
petition notes that approximately 63 percent of all funds spent on bald 
eagles comes from agencies other than AGFD.
Response to Petition
    Information in our files indicates that funding for the ABENWP 
comes from a variety of sources, including State Wildlife Grants, 
donations, AGFD Heritage Funds (State lottery), and matching funds for 
Federal grants. The petitioner's contention that funding for the 
program will be significantly reduced or discontinued in the future is 
    With regard to management and existing regulatory mechanisms, we 
evaluated whether a difference exists between the regulatory mechanisms 
currently protecting the bald eagle in the lower 48 States of the 
United States (inclusive of Sonoran Desert bald eagles) as a threatened 
species and the regulatory mechanisms protecting an endangered species 
(i.e., the petitioned action). As a threatened species with no special 
rule under section 4(d) of the Act, the bald eagle in the lower 48 
States of the United States (inclusive of Sonoran Desert bald eagles) 
is provided protection equal to that of an endangered species under the 
Act, except for penalties for illegal take. The prohibitions of the Act 
make it illegal for any person subject to the jurisdiction of the 
United States to take (includes harass, harm, pursue, hunt, shoot, 
wound, kill, trap, or collect, or to attempt any of these), import or 
export, ship in interstate commerce in the course of commercial 
activity, or sell or offer for sale in interstate or foreign commerce 
any listed species. It is also illegal to possess, sell, deliver, 
carry, transport, or ship any such wildlife that has been taken 
    Further, the Service proposed to remove the bald eagle in the lower 
48 States from the List of Endangered and Threatened Wildlife on July 
6, 1999 (64 FR 36454) and reopened the comment period on that proposal 
on February 16, 2006 (71 FR 8238). The comment period was extended on 
May 16, 2006 (71 FR 28293). If this delisting action were to be 
finalized, we believe other existing regulatory protections afforded 
the Sonoran Desert bald eagle will provide adequate regulatory 
protection to this population. Our determination is based on the 
analysis with our delisting proposal and the fact that the existing 
regulatory protections are national in scope and not specific to the 
population level of a species. With regard to these existing regulatory 
protections, please reference the February 16, 2006 notice (71 FR 
8238), reopening the comment period on the proposed rule to delist the 
bald eagle in the lower 48 States. In this notice, we provide an in-
depth discussion of the protections afforded the bald eagle (including 
the Sonoran Desert bald eagle) by other Federal wildlife laws, 
including the Bald and Golden Eagle Protection Act (BGEPA) (16 U.S.C. 
688-668d) and the Migratory Bird Treaty Act (MBTA) (16 U.S.C. 703-712). 
In summary, the BGEPA prohibits taking, or possession of and commerce 
in, bald and golden eagles, with limited exceptions. Take under the 
BGEPA is defined as ``to pursue, shoot, shoot at, poison, wound, kill, 
capture, trap, collect, molest or disturb'' (16 U.S.C. 668c). The MBTA 
implements various treaties and conventions between the United States 
and other countries and, unless permitted by regulations, it provides 
that it is unlawful to pursue; hunt; take; capture; kill; possess; 
offer to sell, barter, purchase, deliver; or cause to be shipped, 
exported, imported, transported, carried, or received any migratory 
bird, part, nest, egg or product, manufactured or not.
    Based on information provided by the petitioner and noted above, we 
find that no measurable difference exists between the regulatory 
protections provided the Sonoran Desert bald eagle in its current 
status as threatened than if it were assigned an endangered status 
(i.e., the petitioned action). Furthermore, we believe that other 
existing Federal wildlife laws will continue to provide adequate 
regulatory protections to the Sonoran Desert bald eagle if the bald 
eagle is delisted. Thus, we find the petitioner did not provide 
substantial information to lead us to believe that existing regulatory 
mechanisms may be inadequate to protect the Sonoran Desert bald eagle.
Habitual Violation of Law and Lack of Agency Resolve
    The petition states that the Service has been engaged in efforts to 
downlist the bald eagle since at least 1989. The petition notes an 
attitudinal change accompanying downlisting efforts, and that this 
change contributes to increasing threats to the continued existence of 
the Sonoran Desert bald eagle. Specifically, the petition contends that 
the attitudinal shift perpetuates: (a) Cattle grazing within riparian 
habitat critical to Sonoran Desert bald eagles;

[[Page 51559]]

(b) dam operations with water releases that are improperly timed for 
replenishment of riparian nest trees; (c) dewatering of remnant, free-
flowing rivers; (d) introduction of exotic fishes in native fish 
habitat; (e) continuing and increasing low-flying aircraft; and (f) 
approval of excessive amounts of take of Sonoran Desert bald eagles. 
The petition provides detailed information for each of these 
categories, which is summarized below.
    (a) Cattle Grazing Within Riparian Communities--The petition notes 
that cattle grazing in riparian areas is known to impede growth of 
replacement cottonwood nest trees (AGFD 1999a, 2000). The petition 
cites numerous biological opinions by the Service as stating that 
riparian community loss is due, in part, to livestock grazing; that 
overgrazing continues as a threat and disturbance to bald eagles; and 
that overgrazing exacerbates adverse effects to riparian growth, as 
well as to existing eagle nesting, perching, and foraging habitat 
(USFWS 2001a, 2002a, 2002b, 2003b).
    (b) Dam Operations Result in Improperly Timed Water Releases--The 
petition notes that poorly timed water releases are a threat to 
riparian communities (Stromberg et al. 1991). The petition further 
notes that loss of riparian communities continues on the lower Verde 
and Salt Rivers as a result of dam operations, and that maintenance of 
existing water development features, such as dams or diversion 
structures, is a continuing threat and disturbance to bald eagles 
(USFWS 2001a, 2003b). The petition contends that dam operations degrade 
existing eagle tree nesting and perching habitat and retard riparian 
regeneration; alter the hydrological regime of the lower Verde River by 
reducing the magnitude, frequency, and duration of high flow events; 
and restrict the flow of sediment, decreasing recruitment of early 
successional riparian species. The petition indicates that the effects 
of dams and their operation are the most important limiting factors in 
shaping the riparian plant community (Beauchamp 2002).
    (c) Dewatering of Remnant, Free-flowing Rivers--The petition notes 
that flows in the Verde River have decreased to as low as 12 cubic feet 
per second (cfs) (3 cubic meters/second) during the month of June in 
some years (Verde Natural Resources Conservation District 1999). The 
petition also notes that increasing groundwater pumping by the growing 
human population of Cottonwood and Camp Verde, which threatens to 
render sections of the Verde River intermittent (USFWS 1998). The 
petition further notes that the Arizona Department of Water Resources 
(ADWR) found that the Verde River baseflow is provided by groundwater 
discharge from the alluvium and Verde Formation, so any withdrawal from 
this aquifer is expected to eventually deplete Verde River flows (ADWR 
1994). The petition again notes that the human population in Cottonwood 
and Camp Verde is expected to grow by 148 and 158 percent, 
respectively, between 1994 and 2040 (ADES 1994). The petition also 
notes that Prescott and Prescott Valley are developing a plan to use 
water from the Big Chino Basin, which may affect groundwater discharge 
into the upper Verde River (Arizona Republic 2000, 2001).
    (d) Exotic Fish Introductions--The petition notes one study that 
found native fish populations to be a crucial component to suitable 
breeding habitat (Hunt et al. 1992). The petition indicates that at 
least 50 species of nonnative fish have been introduced into the Gila 
River basin (USFWS 2001a), with potentially another 10 to 15 incidental 
occurrences of other nonnative species. They note that nonnative 
species are considered to be extremely difficult, if not impossible, to 
remove once established (Aquatic Nuisance Species Task Force 1994). 
They also note that, in order to manage for native species, fish 
barriers are planned in areas like the upper Verde River, and that 
construction and maintenance of those barriers may result in take of 
bald eagles through harassment or harm due to the use of mechanized 
equipment, dredging of river channels to remove excess sediment, 
completion of required repairs, and added human activity to the area. A 
discussion under Factor E below indicates the petition's concern on the 
decline of native species, especially Sonora sucker and desert sucker 
and their use by bald eagles as prey.
    (e) Continued and Increasing Low Flying Aircraft--The petition 
notes that there have been increases in low-flying aircraft, including 
private, military, and emergency aircraft, and that these aircraft are 
a concern for BAs on the lower Salt and Verde Rivers and for those BAs 
under military training routes (AGFD 1999a, 2000). The petition cites 
examples of aircraft recorded less than 150 feet (45.7 meters) over 
active nests. The noise disturbance and sonic booms produced by 
military aircraft can flush incubating adults from the nest. The 
petition notes that the AGFD has worked with the Federal Aviation 
Administration and the Arizona Department of Transportation to 
establish a 2,000-feet (610-meters) above ground-level advisory along 
the Salt and Verde Rivers, but although marked on Arizona aeronautical 
maps, this advisory is generally disregarded.
    The petition notes that a biological opinion evaluated the 
Department of the Air Force proposal to widen and/or realign segments 
of military training routes in Arizona in 1994 (USFWS 1994c). According 
to the petition, the Service acknowledged the loss of 9 eagles or eggs 
and 18 disturbances per breeding season each year over the 50-year life 
of the project. Disturbances in the biological opinion are defined as 
aircraft use that results in the interruption of breeding or foraging 
activities, including the flushing or displacing of eagles engaged in 
breeding or foraging activities (USFWS 1994c).
    (f) Excessive Service Approval of Sonoran Desert Bald Eagle 
Deaths--The petition contends that the Service has approved Federal 
activities responsible for the deaths of at least 29 Sonoran Desert 
bald eagles in the last decade and claims that Federal activities 
reviewed by the Service through section 7 of the Act will result in a 
cumulative 491 taking deaths over the next 50 years (USFWS 1992d, 
1993a, 1994c, 1996b, 1997b).
Response to the Petition
    As required by section 7 of the Act, we have consulted on the 
potential impacts of cattle grazing, dam operations, dewatering of 
rivers, introduction of exotic fishes in native fish habitat, and low-
flying aircraft to eagles and their habitat. Such analyses within 
biological opinions do not indicate a lack of agency resolve. It is our 
responsibility, under the Act, to enter into consultation with Federal 
action agencies when activities they authorize, fund, or carry out may 
affect a listed species or its critical habitat. During this process, 
we evaluate the impacts of the proposed project on listed species and 
determine how such impacts may be minimized and whether or not the 
project will jeopardize the continued existence of the species. If the 
project does not result in a jeopardy determination, we are responsible 
for working with action agencies to develop reasonable and prudent 
measures that will minimize the adverse impacts of the action on the 
species under consultation. Reasonable and prudent measures are 
restricted to actions that result in only minor changes to the proposed 
project and are within the legal authority and jurisdiction of the 
agency or applicant to carry out.
    The biological opinions cited within the petition analyze the 
impacts of various activities on the bald eagle and

[[Page 51560]]

its habitat, assess whether incidental take will occur, make a 
jeopardy/no jeopardy determination, and provide reasonable and prudent 
measures to minimize incidental take, when appropriate. In addition, 
each consultation includes sections on environmental baseline and 
cumulative effects, which are used to evaluate the effects of the 
current action against the background of previous impacts and total 
expected take for the species. For each of these opinions, we provided 
a take statement and determined that the level of take authorized would 
not jeopardize the continued existence of the species. These indicate 
that, although there may be some level of adverse effect resulting from 
the agency's action, we do not believe the threats imposed by the 
various actions, when considered cumulatively with previous actions, 
were likely to jeopardize the continued existence of the species.
    We do not believe, based on the above discussion, we have 
authorized excessive levels of take for bald eagles in the Southwest. 
It is important to note that we believe the high level of take 
described in the petition with respect to the items E and F above is a 
misinterpretation on the part of the petitioners. The petition 
indicates that, for one consultation regarding expansion of military 
training routes, we allowed for the loss of 9 eagles or eggs and 18 
nest disturbances annually over the 50-year life of the project. We 
provided a take statement for overhead flights that allows for take in 
the form of direct mortality of one adult or immature bald eagle, bald 
eagle nestling, or bald eagle egg, or two instances of disturbance per 
active nest per nest season. Incidental take in the form of mortality 
of more than one eagle, nestling, or egg would require the Air Force to 
reconsult immediately. Further, the reasonable and prudent measures 
require the Air Force to avoid active bald eagle BAs during the 
breeding season. The total take for this opinion was therefore 1 bald 
eagle mortality over the life of the project and 18 disturbance events 
per year (2 at each of 9 BAs) outside of the breeding season each year 
for the life of the project. The total mortality associated with this 
particular project is therefore 1 bald eagle, rather than the 450 
attributed to it in the petition (USFWS 1994, p. 13).
    With regard to existing protections afforded the bald eagle, we 
briefly discuss above the protections afforded the bald eagle under the 
Act (through listing as a threatened species and other Federal wildlife 
laws including the Bald and Golden Eagle Protection Act (BGEA) (16 
U.S.C. 668-668d) and the Migratory Bird Treaty Act (MBTA) (16 U.S.C. 
703-712). We also explain why we believe these protections are adequate 
to protect the bald eagle and maintain recovered population levels. For 
a more in-depth discussion of these protections, please reference the 
February 16, 2006, notice reopening the comment period on the proposed 
rule to delist the bald eagle (71 FR 8238).
    We find that the petitioner did not provide substantial information 
to lead us to believe that existing regulatory mechanisms are 
inadequate to protect the Sonoran Desert bald eagle. We find that much 
of the information provided by the petitioner is speculative (e.g., 
reduced funding as a result of delisting) and not reliable (e.g., 
approval of excessive take). Additional information provided by the 
petitioner with regard to cattle grazing, dam operations, dewatering, 
introduction of exotic fishes, and low-flying aircraft does not 
establish a connection to the petitioned action, and does not indicate 
theses actions are occurring at a level that makes the Sonoran Desert 
bald eagle in danger of extinction (i.e., ``endangered'' as defined 
under the Act). As noted above in the Species Description, the numbers 
of occupied BAs in the Sonoran Desert population of bald eagles has 
continued to increase, reaching a total of 36 occupied BAs in 2004. 
Productivity has remained relatively constant between 1987 and 2005, at 
an annual average of 0.78 young per occupied BA for the Sonoran Desert 
population. This rate is within the range of many other states' 
productivity rates (AGFD 2006, p. 5).

E. Other Natural or Manmade Factors Affecting Its Continued Existence

Small Population Size
    The petition notes that bald eagles once nested along every major 
river and large lake in the continental United States, and that they 
are no longer found in all areas of their historical range (Gerard and 
Bartolotti 1988). The petition further notes that the Sonoran Desert 
population of the bald eagle is extremely small and without prospect 
for significant expansion. The petition notes that there are fewer than 
60 nesting pairs of bald eagles in the population, and that the 
population occupying BAs may be overestimated. Their concern for 
overestimation of the population is based on the fact that members of 
breeding pairs recorded as occupying, but not breeding, in a BA may 
also occupy adjacent BAs. They note that two males were observed to 
move between BAs, and it is possible that adults recorded as occupying 
one BA may have come from an adjacent occupied BA.
    The petition notes that BAs may have been occupied in years prior 
to their discovery, and that, if this is the case, the continued 
increase in the number of BAs represents an increase in the number of 
discovered BAs, rather than an increase in the actual number of 
breeding birds. Undercounting of the population in previous years has 
resulted in a greater discrepancy between past and current known 
numbers of breeding birds, which reflects a greater increase in the 
population than that which might actually have occurred.
    The petition further notes that there is not enough surviving 
suitable habitat available to allow for the population to increase 
substantially or expand its distribution. They note that the AGFD has 
concluded that riparian community improvement and prey base 
modifications will be necessary before population sizes increase in 
Arizona (AGFD 1999, 2000). Thus, the petitioners believe that the 
Sonoran Desert population will likely continue to remain small into the 
foreseeable future.
    The petition notes that the small size of the Sonoran Desert bald 
eagle population is, in and of itself, problematic. Using AGFD survival 
estimates of juveniles and nestlings, the petitioners estimate that 
there are approximately 166 individual eagles in the Sonoran Desert 
population. The petition maintains that the population dynamics of such 
a population are essentially similar to those of an isolated 
metapopulation. The petition references a study examining the effects 
of widespread habitat destruction on regional metapopulations of 
raptors, and notes that the study found most species persist regionally 
as metapopulations or as sets of populations linked by dispersing 
individuals (Thomas et al. 1990). This allows for recolonization of 
unoccupied habitat patches following local extinction events. However, 
the petition states that the loss of suitable habitat patches, or 
disturbances in the surrounding landscape, can disrupt this process and 
lead to the regional extinction of a species. The cited study indicates 
that the persistence of the raptor species is at risk in significant 
portions of its range due to continued destruction and concomitant 
fragmentation of its habitat. As this pattern continues, a previously 
continuous population is separated into smaller, isolated demographic 
units that are at higher risk of local extinction due

[[Page 51561]]

to demographic factors and/or environmental phenomena.
    The petition contends that four ``categories of analysis'' are 
applicable to the question of the long-term survivability for raptors 
in general, including demographics, genetics, patch dynamics, and 
environmental change. The petition indicates that, based on population 
biology principles, if a typical vertebrate species such as a raptor is 
reduced to a genetically effective size of 50, it may suffer from 
inbreeding depression (Barrowclough and Coats 1985; Franklin 1980; 
Soule 1980). Further, demographic stochasticity and inbreeding 
depression may interact, with the effects of one exacerbating the 
other, and hasten the decline of a population (Gilpin and Soule 1980). 
The petition states that populations that are reduced in size tend to 
lose genetic variability through genetic drift, reduced average 
individual heterozygosity, and a reduced pool of allelic variation. The 
petition contends that a population size of roughly 1,000 or larger is 
required to maintain all of the genetic variation of that population 
(Soule 1986). Below that size, the population will lose genetic 
variation at a rate proportional to the size of the population. The 
petition concludes that the Sonoran Desert population has 
characteristics of extended adult longevity, high juvenile mortality, 
intense territoriality, and may be in a position to enter a geometric 
population decline (Lande 1987).
    The petition, which notes adult mortality is higher than 
recruitment for the population, contends that the level of mortality in 
the Sonoran Desert population is higher than can support a stable 
population. The petition states that, from 1987 to 1990, the rate of 
mortality for breeding-adults has averaged 16 percent of the breeding 
population per year or 5.25 breeding adult mortalities per year. From 
1991 to 1998, the rate of mortality was 11.9 percent, or 5.13 breeding-
adult mortalities per year (Beatty and Driscoll 1996; AGFD 1999a, 
    The petition further contends that the high presence of subadults 
in breeding pairs likely reflects high adult mortality rates. The 
petition notes that Hunt et al. (1992) indicated that the presence of 
subadults in breeding pairs may show that excessive adult mortality is 
draining the floating (i.e., non-breeding) segment of adult bald 
eagles. As a result, subadult eagles are recruited into the breeding 
population, either forming a new pair bond with another non-breeding 
bird, or more frequently, replacing the mate of another breeding eagle. 
Twelve subadult-plumaged birds were observed holding territories in 
Arizona from 1987 to 1990, with seven subadult-plumaged birds observed 
holding territories in Arizona since 1991. The petition notes that the 
AGFD (1994b) found that, for 39 known vacancies of BAs, 15 (38.5 
percent) were filled by adults and 24 (61.5 percent) by near-adults or 
subadults. The petition states that this pattern is not observed in 
other populations (Gerrard et al. 1992), and that in Saskatchewan, 
population stability was maintained in part by bald eagles deferring 
first breeding to age six. The petition states that a 1992 survey of 14 
bald eagle biologists throughout North America determined that the 
known incidence of breeding subadults outside of Arizona was 0.02 
percent (Hunt et al. 1992). The petition concludes that the persistent 
presence of three- and four-year-old breeding bald eagles in Arizona 
has created concern for the health of the breeding population.
    The petition contends that mortality for fledglings is also 
excessive, and that most Sonoran Desert nestlings die prematurely. The 
petition notes that, according to AGFD data, from 1987 to 1998, 97 
fledglings have been found dead (Hunt et al. 1992; Mesta et al. 1992; 
Beatty and Driscoll 1996b; AGFD 1991, 2000), and concludes that few 
Sonoran Desert bald eagles survive to adulthood.
    The petition states that the reproductive rates for the Sonoran 
Desert population are lower than those known for bald eagles in any 
other location. The petition indicates that the AGFD (1999a, 2000) 
determined that productivity rates are lower than those recorded 
throughout North America. For the Sonoran Desert population, 
productivity rates from 1975 to 1984 were 0.92 young per occupied BA, 
but since then, the average productivity rate has been 0.78 young per 
occupied BA. The petition notes that productivity rates over a similar 
time span in Alaska, Florida, Washington, and Wisconsin averaged 0.96 
young per occupied BA (Sprunt et al. 1973; McAllister et al. 1986; 
Kozie and Anderson 1991). The petition adds that, in some areas of the 
Sonoran Desert population, productivity rates are even lower. For 
example, productivity along the Salt River declined to 0.26 young per 
occupied BA in the 1990s.
    The petition further contends that BAs that formerly produced the 
majority of the fledglings are producing fewer fledglings, and that the 
most productive nests are in relatively close proximity to the rapidly 
growing Phoenix metropolitan area, so that survivability in these BAs 
is becoming increasingly problematic. The petition states that the Salt 
and Verde Rivers support the bulk of the Sonoran Desert population, and 
that it is in the lower parts of these drainages and nearby lakes where 
prey is most abundant and bald eagles are most productive. However, the 
proximity of these areas to Phoenix results in high recreation use. Due 
to predicted human population expansion (see factor A above), the 
petition predicts increased recreational and development pressures in 
close proximity to BAs along the Salt and Verde Rivers (ADWR 1999a, 
2000; Arizona Republic 2000, 2001; Chino Valley Review 2004; Prescott 
2001; Prescott Daily Courier 2004a, 2004b; USFWS 2001a).
    The petition further notes that Sonoran Desert bald eagles on 
private lands are either not reproducing or are destined to fail. The 
petition cites the Winkelman BA as an example, noting that this BA on 
private property is now surrounded by housing, recreation, and 
industry. The petition states that the Camp Verde and Perkinsville BAs 
are also on private property, and are surrounded by private lands that 
have recently been sold or for which plans to sell are underway. The 
petition cites the reproductive history of these BAs, noting that the 
Camp Verde and Winkelman BAs have a record of reproductive failure, and 
that the Perkinsville BA failed in 2002 and faces further threats from 
potential dewatering of the upper Verde River.
    The petition includes information developed by the petitioners 
through the use of Vortex (version 9) software, which models wildlife 
population dynamics and evaluates many of the threats that may cause 
small populations to go extinct. The petition notes that the 
petitioners worked with AGFD data. Some of the model assumptions are 
that the population is a closed population and not demographically 
linked to other populations, and that there is a 1:1 ratio of males to 
females in the adult population. Because the petitioners determined 
that fecundity in the lower Verde and Salt BAs were inflated 
artificially by AGFD's stocking of exotic rainbow trout and Salt River 
Project's release of native fish captured from irrigation canals, BAs 
were divided into two groups: (1) Those on the lower Salt and Verde 
Rivers, and (2) those in other areas.
    Additional detail regarding parameters used in and determinations

[[Page 51562]]

derived from the model are in the petition. The petition notes that the 
model determined that juvenile and adult survival were the most 
critical parameters for the model. The petition indicates that the 
model demonstrates a high risk of extinction for the Sonoran Desert 
population within the next 57 to 82 years.
Response to the Petition
    The majority of the data and information presented in the petition 
is, in part, consistent with the information in our files. Our 
information indicates, however, that there are no data supporting the 
statement that nests on private property are destined to fail simply 
due to their location relative to private land. While it is true that 
the Winkelman BA has been abandoned, the Camp Verde nest may have 
failed due to flooding, which is unrelated to the land's ownership. 
Moreover, two BAs on private land (Sheep and Beaver) are currently 
occupied and produced young in 2005 and 2006, respectively.
    In addition, we do not believe the population is overestimated due 
to individuals occupying more than one BA; this behavior has been 
observed at only two BAs, and the survey protocols and definition of 
occupancy currently in use limit this type of bias from occurring (E. 
Gardner, pers. comm. 2006, p. 3).
    With respect to mortality, AGFD (2006c, p. 24) notes that adult 
mortality rates of 16 percent (from 1987 to 1990) and 12 percent (from 
1991 to 1998) are higher than, but within the range of, other 
populations, which ranged from 5 percent in Northern California to 17 
percent in Chesapeake Bay. Bald eagles in Maine experienced a nine-
percent mortality rate, while those in Coastal Alaska were a 12-percent 
mortality rate.
    For nestling mortality, the petition concluded that few Sonoran 
Desert bald eagles survive to adulthood. Stalmaster (1987, p. 143) 
found that, of 433 nestlings surveyed in the southwestern region, an 
average of 85 percent survived to fledging, resulting in a mean 
nestling morality rate of 15 percent. By comparison, Hunt et al. (1992, 
p. C-108) concluded that the nestling mortality rate for the Arizona 
population was approximately 0.9 percent higher, or at 15.9 percent. 
Following Hunt's study, from 1991 to 2006, nestling mortality was 
approximately 24 percent. While this represents an eight percent 
increase from data provided by Hunt et al. (1992, p. C-108), this may 
be due to increased monitoring effort through the ABENWP compared to 
earlier Arizona monitoring efforts and those efforts in other states. 
Daily monitoring through the ABENWP, monthly helicopter flights, and 
periodic on-the-ground visits throughout the year may have more 
accurately detected surviving fledglings and fledgling mortality than 
efforts that involved fewer follow-up visits. While we believe this 
nestling mortality rate warrants continued monitoring, a 76-percent 
survival rate does not indicate that most Sonoran Desert nestlings die 
prematurely, as contended by the petition.
    The information provided by AGFD (2006c) and Stalmaster (1987) 
indicate that mortality rates for bald eagles within the Sonoran 
breeding population are similar to those experienced in other 
populations in the United States, as are productivity rates. In 
addition, the population has continued to increase in terms of the 
number of breeding pairs and productivity, as noted above under the 
``Species Information.'' Therefore, we find that the petitioner did not 
provide substantial information to indicate that the level of mortality 
and small population size may place the Sonoran Desert population of 
bald eagle in danger of becoming extinct.
Declining Prey Base
    The petition notes that the primary prey item for bald eagles 
during spring is the native Arizona sucker population, consisting of 
desert and Sonora suckers. The petition cites recent reports indicating 
that Sonora sucker and desert sucker remain in approximately 73 percent 
and 74 percent, respectively, of the locations in which they were 
historically recorded. These fish populations have a low probability of 
local extirpation, but fragmentation of their range and isolation of 
individual populations could further reduce their occurrence in a 
watershed (Desert Fishes Team 2004). With respect to the potential 
effects of a decline in the native fish prey base, the petition quotes 
the biological opinion completed for the Central Arizona Project (CAP) 
(USFWS 2001a). The petition indicates that in the CAP opinion the 
Service concluded that take of bald eagles was anticipated to occur as 
harm, through alteration of the quantity and quality of the food base.
    The petition cites, as a specific example, the effects of the 
decline of native suckers on the Salt River. The petition states that 
native suckers, which are a crucial prey species during the breeding 
season for bald eagles, became absent from the Salt River during the 
1990s. The petition cites studies that note that the lack of native 
fish species along those portions of the Salt River occupied by bald 
eagles may have reduced productivity from 0.69 young per BA in the 
1980s to 0.26 in the 1990s (Hunt et al. 1992).
Response to the Petition
    The petition presents reliable and accurate information to indicate 
that native fishes are continuing to decline and effects to the prey 
base can have effects on the Sonoran Desert population of bald eagles. 
As outlined below, the effects of a reduced prey base seem to be 
affecting productivity rather than occupancy. Occupancy of these BAs 
remains fairly constant through 2002. Between discovery in 1978 and 
2002, the Cedar Basin BA was unoccupied for only 1 year (1980). The 
Canyon and Pinal BAs were unoccupied for 2 years each (2001 and 2002 
for the Canyon BA, 1986 and 2001 for Pinal). The Cibecue BA was 
unoccupied for 3 years (1974, 1976, and 1981). The Lone Pine and 
Redmond BAs have remained occupied since their discoveries in 1984 and 
1975, respectively (AGFD 2006, Table 7, pp. 48-50). Two BAs, Ash and 
Mule Hoof, are no longer considered occupied. The Ash BA was occupied 
in 1984 and 1985, but has been unoccupied for 10 consecutive years, and 
is no longer included in the list of occupied BAs. Mule Hoof was 
sporadically occupied in the 1980s and the early 1990s, and was removed 
in 2002 after 10 consecutive years of unoccupancy (AGFD 2006, Table 7, 
pp. 48-50).
    However, while the upper Salt River BAs have remained largely 
occupied, productivity for the six BAs has remained low, declining 
after 1992 although remaining somewhat constant. From 1992 to 2002, 
between 0 and 3 total young have been produced each year (AGFD 2006, 
Table 7, pp. 48-50).
    Hunt et al. (1992, p. A-46) note that bald eagles in central 
Arizona forage on free-flowing and regulated rivers, reservoirs, small 
tributary streams, and on land, and that most, if not all pairs, use 
more than one of these environments during a given nesting season. Data 
indicate eagles commonly switch forage locations and/or prey species in 
response to changes in the distribution of prey and carrion. Hunt et 
al. (1992, p. A-46) cite as an example a study on a male eagle from the 
Blue Point BA that took a variety of prey on both reservoir and 
riverine habitats. While those BAs that rely primarily on riverine 
habitat for prey, such as those in the upper Salt River, are showing a 
reduction in productivity, overall productivity for bald eagles 
throughout Arizona and within the Sonoran Desert population has 
remained stable between 1987 and 2005, and is comparable to

[[Page 51563]]

that in other portions of the species range.
    As the petitioners note, low productivity has been an issue on the 
upper Salt River since the 1980s. However, as noted above, the BAs in 
this area continue to remain occupied, and productivity, while low, 
remains fairly constant. Consequently, we do not perceive a new or 
increased threat due to a reduced prey base in this area. The situation 
on the upper Salt River is likely observed in other streams as well, 
where eagles rely primarily on rivers for foraging. This situation 
requires continued monitoring, and improvements need to be made in 
managing for native fishes, and increasing overall productivity in 
these BAs. However, there has been increased productivity in other BAs, 
including some of those that also rely on rivers for foraging. This 
increase is in part attributable to the increase in the total number of 
BAs throughout Arizona. Therefore we find that the petitioner did not 
provide substantial information to indicate that threats from 
reductions in prey base are occurring at a level that leads us to 
conclude that the petitioned action may be warranted.
    The petition claims that insecticides, such as carbofuran, 
endosulfan, fenthion, phorate, and terbufos (American Bird Conservancy 
2004a, 2004b; Center for Biological Diversity 2004c; EPA 2004c, 2004d, 
2004e, 2004f; University of Arizona 2004; USDA 2001; USFWS 1995), 
continue to threaten the bald eagle, noting that hundreds of bald eagle 
deaths have been linked to carbofuran nationwide (American Bird 
Conservancy 2004b). The petition further states that DDT and its 
derivatives are still found in Arizona waterways, and states that toxic 
levels of DDE (a breakdown product of DDT) were found in an addled egg 
from the Sycamore BA in 1997 (AGFD 1999a, 2000; USGS 2004).
    The petition notes that chlorfenapyr resulted in a decline in the 
number of eggs, viable embryos, and hatchlings of mallards, and that 
this chemical has been put to use within the United States (EPA 1999). 
The petition further states that toxic levels of mercury have been 
found in eggs from the Verde and Salt River BAs, and that mercury 
contamination has also been found in the Tonto Creek BA and Gila River 
at levels high enough to cause failure in eggs (AGFD 1999a, 2000). The 
petition notes that mercury concentrations in the Sonoran Desert 
population were higher than those reported for most other North 
American populations (Grubb et al. 1990). The petition states that 
studies have determined that concentrations of mercury above 2 parts 
per million (ppm) are known to impair hatching (Newton 1979), and 
concentrations of 1.5 to 4.5 ppm are considered toxic (Ohlendorf 1993). 
The petition notes tha seven eggs from the Tower, 76, Pinal, and 
Winkelman BAs have toxic levels of mercury ranging from 2.11 to 8.02 
ppm, and that elevated levels of mercury between 1.5 and 2.0 ppm were 
found in three eggs from the Tower and Horseshoe BAs (AGFD 1999a, 
2000). The petitioners note that the Service considered concentrations 
of heavy metals to be a concern in Arizona (USFWS 2001d).
    The petition contends that mercury in bald eagles comes primarily 
from their prey, noting that contaminants studies detected elevated 
levels of mercury in prey items ranging from 0.06 to 0.97 micrograms 
per gram ([mu]/g) with the highest mean levels recovered from Lake 
Pleasant, the Salt River, and Alamo Lake (King et al. 1991). The 
petition contends that these highest means were above the National 
Contaminant Biomonitoring Program's recommendation for no observable 
effects of 0.1 [mu]/g (Eisler 1987).
    The petition notes that methylmercury is the form of mercury that 
accumulates at greater rates than inorganic mercury, and that most 
mercury in fish or wildlife organisms is in the form of methylmercury 
(Bloom 1989). The petitioners further note that methylmercury is more 
efficiently absorbed (Scheuhammer 1987) and preferentially retained 
(Weiner 1995).
    The effects of mercury contamination have been studied in mallards. 
The petition cites a study on the effects of mallards that were fed 3.0 
ppm methylmercury dicyandiamide for 2 years. In these mallards lesions 
resulted, including necrosis and hemorrhaging in the lining of the 
brain (Heinz and Locke 1975). The petition contends that the risk to 
bald eagles is increasing, as eggs collected between 1982 and 1984 had 
concentrations of approximately 0.39-1.26 ppm (K. King, pers. comm.), 
while those collected between 1994 and 1997 had concentrations ranging 
from 2.11 to 8.02 ppm (Beatty et al. unpub. data), up to six times 
higher than those collected between 1982 and 1984.
Response to the Petition
    The petition provides information specific to bald eagles in 
Arizona to indicate that contaminants (in the form of DDT and related 
breakdown products, and mercury) continue to present a potential threat 
to the Sonoran Desert bald eagle population. We find that some of the 
information presented by the petitioner is in error. With respect to 
carbofuran, it is important to that note the granular form that caused 
the extreme risks in grain-eating birds is not registered for use in 
Arizona (Extoxnet 2006, p. 1). Similarly, chlorfenapyr is not 
registered for use in Arizona (EPA 2006, p.1).
    The discussion on mercury indicates that mercury levels were found 
to exceed 2 ppm for 13 eggs collected between 1994 and 1997. AGFD 
(2006, p. 21) notes that, from 1994 to 2004, 27 addled bald eagle eggs 
in Arizona showed mercury levels ranging from 0.55 to 8.02 ppm. The 
AGFD (2006, p. 21) classifies 10 of these eggs as toxic, exceeding 2.0 
ppm; 11 eggs as having elevated levels of mercury (1.5 to 2.0 ppm), and 
four eggs as having lesser concentrations (1.0 to 1.5 ppm). The 10 eggs 
classified as toxic came from the Box Bar, Needle Rock, Pinal, 76, 
Tower, and Winkelman BAs. While eggs tested for mercury were addled and 
did not produce young, successful production of young has occurred at 
these BAs following the year or years in which mercury was detected 
(viable eggs are not collected and tested for mercury). For example, 
with toxic mercury levels in 2003, the Box Bar BA successfully produced 
young in 2004 and 2005. Following toxic mercury level detection in 
2003, the Needle Rock BA successfully produced young in 2004. Following 
toxic mercury levels in 1995, the Pinal BA successfully produced young 
in 2000, 2002, 2004, and 2005. The 76 BA, which had the highest ever 
recorded mercury level for eggs from Arizona in 1995, successfully 
produced young in 1996, 1997, 1998, 1999, 2000, and 2001. Following 
toxic mercury level detection in 1994 and 1995, the Tower BA 
successfully produced young in 1996, 1997, 1998, 1999, 2000, 2002, 
2003, and 2005. No information is available for the Winkelman BA, which 
has been unoccupied since 1999. These data indicate that mercury in 
eggs at a given nest site may cause nest failure for one season, but 
does not prevent future production of young.
    DDE does continue to be detected in eggs, with the recent 
measurement of 4.23 ppm wet weight in one egg from the Rodeo BA in 
2002. Weimeyer et al. (1984, p. 541) found that reductions in 
productivity occurred when DDE values in bald eagle eggs were between 3 
and 5 ppm (wet weight). This level has been reached at the Tonto, 
Tower, Sycamore, and Rodeo BAs. The most complete DDE data set over 
time is from the Tower BA, where DDE concentrations declined from 3.2 
ppm in 1994, to 0.91 ppm in 2001. The Tonto BA has

[[Page 51564]]

produced young since DDE levels of 4.17 ppm wet weight were found in 
q2001. Following DDE levels of 3.20 ppm wet weight, the Tower BA 
produced young in 1996 through 2003, 2005, and 2006. At the Sycamore 
BA, DDE levels of 7.00 ppm wet weight were detected from an egg 
collected in 1997, but the BA produced young in 1998, 1999, and 2001 
through 2006. The Rodeo BA, with DDE levels of 4.23 ppm in 2002, 
produced young in 2004 and 2006 (AGFD 2006, Table 4, p. 22; 2006 
unpubl. data).
    The information presented on the mercury levels found in eggs from 
the Verde and Salt River BAs is generally accurate, as is that for the 
Tonto Creek and Gila River area. The information on DDT and its 
breakdown products is also generally accurate. Productivity at those 
BAs affected by high levels of mercury and DDE indicates that, while 
nest failure may result when those levels are detected, young are 
produced in subsequent years. We have been evaluating the effects of 
mercury, DDE, and pesticides for many years, and we conclude that these 
effects should be monitored but are not likely to jeopardize the 
continued existence of the species. We do not believe that the 
petitioner provided substantial information to indicate contaminant-
related threats are present at a level that leads us to conclude that 
the petitioned action may be warranted.
Fishing Line and Tackle
    The petition cites AGFD data that finds fishing line and tackle 
have been found in nests and have entangled bald eagles. There have 
been 62 separate instances involving entanglement, and 19 BAs with 
fishing line and/or tackle in nests or entangled individuals since 1986 
(Hunt et al. 1992; Beatty 1992; Beatty and Driscoll 1994a; Beatty et 
al. 1998). The petition notes that mortalities have resulted from 
entanglement. The petition indicates that bald eagles encounter fishing 
line primarily by catching dead or dying fish with fishing line or 
tackle still attached, but that some birds have become entangled while 
perched on the shoreline or while feeding on dead shorebirds and 
waterfowl that have themselves been entangled.
    The petition states that the persistent occurrence of fishing line 
indicates the level of recreational pressure in many of the BAs, and 
contends that as the human population of central Arizona increases, so 
will the accompanying recreational demands on riparian areas (AGFD 
1999a, 2000). The petition concludes that these increased recreational 
pressures will lead to even greater incidences of fishing line and 
tackle in nests and resulting in adverse effects on Sonoran Desert bald 
Response to the Petition
    The petition does not mention AGFD's monofilament recovery program. 
Although this program is voluntary, it has helped to educate anglers 
and reduce the amount of improperly disposed monofilament. For probable 
causes of mortality in bald eagles in Arizona between 1987 and 2005, 
monofilament is listed as causing one adult mortality and two nesting 
mortalities. It is ranked as the fifteenth most common cause of 
mortality, and responsible for 3 out of 281 deaths, or approximately 
1.1 percent (AGFD 2006, Table 6, p. 25). Monofilament is an ongoing 
problem for Sonoran Desert bald eagles, but represents a minor threat. 
In part, we attribute this to the active management of the ABENWP, 
which we anticipate will continue. Additionally, wildlife personnel 
entering nests to conduct annual banding are instrumental in removing 
large quantities of monofilament (AGFD 2006, p. 11). We find the 
petitioner did not provide substantial information to indicate that 
monofilament entanglement may represent a threat that puts the Sonoran 
Desert bald eagle population in danger of extinction.
Climate Change
    The petition notes that adaptation to the Southwest's combination 
of high temperature and low humidity is considered one of the 
characteristics that demonstrate the uniqueness of the Sonoran Desert 
eagle population. The petition continues, however, to state that heat 
stress is also a leading cause of nestling mortalities. The petition 
notes that the Service (USFWS 1990b) determined that this situation 
will likely become more common, citing more days above 100 
[deg]Fahrenheit in 1990 than 1989. The petitioners indicate that older 
nestlings have fallen from nest cliffs while attempting to reach shade 
or have fledged prematurely from nests without shade, which usually 
results in their mortality. The petition cites studies indicating that 
23 nestlings died and 7 pre-fledged due to heat stress (Hunt et al. 
1992). The petition cites additional information regarding heat-related 
    In addition to heat, the petition notes that global warming will 
lead to more frequent drought cycles. The petitioners note the Service 
(USFWS 2003b) determined that, between 1993 and 2001, eagles that 
depend on Roosevelt Lake for food had lower reproduction as the lake's 
surface area declined.
Response to the Petition
    The petition presents some information to indicate that heat is a 
stressor for the Sonoran Desert bald eagle, and that drought and 
declining water levels at reservoirs may result in decreased 
productivity. The AGFD notes that heat stress is the fourth-leading 
cause of known nestling mortalities, behind predation, parasitism, and 
starvation (E. Gardner, AGFD, pers. comm. 2006). It is ranked as the 
sixth greatest threat to bald eagles in all age classes (AGFD 2006, 
Table 6, p. 25).
    Productivity for the Sonoran Desert population of bald eagles has 
reached its highest level yet for 2003 (at 0.62 young per occupied BA), 
2004 (at 1.06 young per occupied BA), and 2005 (at 1.01 young per 
occupied BA), while the Southwest experienced drought conditions. 
Climate variability and drought conditions may ultimately cause adverse 
effects to the bald eagle; however, the long-term effects of ongoing 
drought for desert-adapted birds like those of the Sonoran Desert bald 
eagle population are unknown. The bald eagle is successful in a wide 
range of climate conditions. We do not find that the petitioner 
provided substantial information to demonstrate that drought and 
increased heat will lead to adverse effects to the Sonoran Desert 
population of bald eagles that would cause them to be in danger of 
becoming extinct. Therefore, we find that the petitioner did not 
provide substantial information to indicate that climate-related 
threats are occurring at a level that leads us to conclude that the 
petitioned action may be warranted.
Eggshell Thinning
    The petition notes that eggshell fragments from 32 Arizona bald 
eagle BAs were collected, measured, and averaged by nest from 1977 to 
1997. These means were then compared with the 0.591 mm mean from Baja 
California, which is the closest known bald eagle population to Arizona 
with pre-DDT eggshell measurements. The petition cites Wiemeyer et al. 
(1984) in noting that eggshell thinning of greater than 10 percent 
causes problems in reproduction for other bald eagle populations. 
Similarly, the petition notes that studies have determined that a 
population would experience reproductive problems when eggshell 
thinning has become severe (15 to 20 percent) for a period of years 
(Anderson and Hickey 1972).
    Mean eggshell thicknesses were compared with those from Baja 
California, which had a mean of 0.591

[[Page 51565]]

mm (0.024 in). The petition cites four studies on eggshell fragments 
for southwestern bald eagles (Grubb et al. 1990; Hunt et al. 1992; 
Mesta et al. 1992, Driscoll and Beatty, unpublished data). The results 
of these studies found eggshell thickness means of 0.539 mm (0.021 in) 
for 32 sets of eggshell fragments from 14 BAs between 1977 to 1985; 
0.562 mm (0.022 in) for 71 sets of eggshell fragments from 23 BAs 
between 1987 and 1990; 0.552 mm (0.022 in) for 27 sets of eggshell 
fragments from 18 BAs between 1991 and 1992; and 0.534 mm (0.021 in) 
for 135 sets of shell fragments collected from 27 BAs between 1993 and 
1997. In comparison to the Baja California mean eggshell thicknesses, 
these studies found a comparative 8.8 percent thinning for 1977 to 
1985; 4.9 percent from 1987 to 1990; 6.6 percent in 1991 and 1992; and 
9.7 percent from 1993 to 1997 (Grubb et al. 1990; Hunt et al. 1992; 
Mesta et al. 1992, Driscoll and Beatty, unpublished data). The petition 
notes that, since 1993, the annual percent thinning exceeded 10 percent 
in 1994 and 1995, and remained high at 9.9 percent in 1996 and 1997.
    The petition notes that the cause of the eggshell thinning is not 
known at this time. While chlordane and DDE were the most frequently 
detected organochlorines in fish sampled near eagle nests, they were 
present at levels below those associated with eggshell thinning in bald 
eagles. The petition further notes that studies found that trace 
elements, especially mercury, were elevated, as were aluminum, arsenic, 
copper, and zinc (Hunt et al. 1992; King et al. 1991).
Response to the Petition
    AGFD (2006c, p. 23) notes that eggshell thinning equaled or 
exceeded 10 percent on 5 separate occasions between 1993 and 2004. 
These occurred in 1994 at 10.7 percent, 1999 at 10.8 percent, in 2000 
at 12.3 percent, in 2003 at 10.7 percent, and in 2004 at 10.0 percent. 
However, AGFD (2006c, p. 23) concludes that, since the ban of DDT in 
1973, other factors may have a greater influence on productivity than 
DDT, but that egg collection and eggshell measurements will continue to 
ensure that the effects of DDT and other organochlorines do not affect 
productivity. We agree with this conclusion, and believe that eggshell 
thinning warrants further study and monitoring; however, at this time, 
we are not aware of any data to indicate thinning at the levels cited 
is resulting in losses of eggs. We find that the petition did not 
provide substantial information to indicate eggshell thinning may place 
the Sonoran Desert bald eagle population in danger of becoming extinct.


    We have reviewed the petition, literature cited in the petition, 
and information in our files. In evaluating this petition, we sought to 
determine if sufficient information was provided to warrant continued 
consideration and development of a 12-month finding. We find available 
genetic studies on bald eagles are dated, the sample size was small, 
and researchers conducting the studies found the results to be 
inconclusive. We therefore believe that the best available genetic 
information is inconclusive with regard to the discreteness of the 
Sonoran Desert bald eagle population. However, we believe the petition 
presents substantial information on distinct morphological features of 
the Sonoran Desert bald eagles with respect to size. Additionally, we 
believe the petition provides substantial information on natal site 
fidelity in breeding birds and the limited number of other eagles in 
neighboring southwestern states or Mexico. Finally, we believe the 
strongest argument presented by the petitioners for a positive 
discreteness finding is provided by the data indicating that 20 years 
of monitoring have resulted in the determination that no eagles have 
immigrated to and only one eagle has emigrated from the Sonoran Desert 
bald eagle population. These three factors lead us to find that the 
petition contains substantial information that the Sonoran Desert bald 
eagle population may be discrete from other bald eagle populations.
    However, on the basis of our review, we find that the petition does 
not present substantial scientific or commercial information to 
indicate that the Sonoran Desert bald eagle constitutes a valid DPS, 
pursuant to the DPS policy (FR 61 4722). Although we believe the 
population to be discrete, the petition does not present substantial 
scientific information that the Sonoran Desert bald eagle may be 
significant in relation to the remainder of the taxon. Therefore, we 
conclude that the Sonoran Desert population is not a listable entity 
pursuant to section 3(15) of the Act. However, recognizing the volume 
of information provided in the petition, and the national importance of 
the bald eagle, we conducted a threats analysis.
    We find that the petition contains detailed information on numerous 
threats affecting the Sonoran Desert population of bald eagles. 
Largely, we are in agreement that these threats are present, and in 
some cases are having some level of effect on Sonoran Desert bald 
eagles. However, as we discuss throughout our responses, no new 
information on threats was presented by the petitioner. Additionally, 
we did not find that the petition presented substantial information 
indicating an increased level of any of the threats discussed. The lack 
of information on new or escalating threats, combined with the 
increased number of occupied breeding areas and increased productivity 
levels, causes us to conclude that the Sonoran Desert bald eagle 
population, while facing threats, continues to increase in numbers of 
adult birds and in productivity. We therefore find that the petition 
did not provide substantial information to lead us to conclude that the 
petitioned action to reclassify the Sonoran Desert bald eagle as 
endangered may be warranted.
    We encourage interested parties to continue to gather data that 
will assist with the conservation of the species. If you wish to 
provide information regarding the bald eagle, you may submit your 
information or materials to the Field Supervisor, Arizona Ecological 
Services Office (see ADDRESSES section above).

References Cited

    A complete list of all references cited herein is available, upon 
request, from the Arizona Ecological Services Office of the U.S. Fish 
and Wildlife Service (see ADDRESSES section above).


    The primary authors of this notice are the staff of the Arizona 
Ecological Services Office (see ADDRESSES).


    The authority for this action is the Endangered Species Act of 
1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: August 21, 2006.
H. Dale Hall,
Director, Fish and Wildlife Service.
[FR Doc. 06-7180 Filed 8-29-06; 8:45 am]