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Endangered
and Threatened Species
With over 90 percent of California’s original wetlands gone, the
Salton Sea has become one of the most important nesting sites and stopovers
along the Pacific Flyway. In some years, as many as 95 percent of the
North American population of eared grebes may use the Sea, 90 percent
of American white pelicans, 50 percent of ruddy ducks and 40 percent
of Yuma clapper rails. All of these species are of concern at either
regional, continental or global scales. With its marine, freshwater,
desert, wetland and agricultural habitats, the Sonny Bono Salton Sea
National Wildlife Refuge provides habitat for hundreds of birds and
wetland species, including several that have been listed as endangered
or sensitive by the U.S. Fish and Wildlife
Service.
Endangered Species
Desert pupfish
Yuma clapper rail
California Bird Species of Special Concern
Burrowing owl
California brown pelican
Mountain plover
Birds of Interest
American white pelican
Black skimmer
Eared grebe
Peregrine falcon
Ruddy duck
Yellow-footed gull
Shorebirds
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Endangered Species
Desert pupfish (Cyprinodon macularius):
The desert pupfish was listed as endangered by the U.S.
Fish and Wildlife Service on March 31, 1986. It is also listed as
endangered by the State of Arizona. Desert pupfish are found in shallow
water of desert springs, small streams, and marshes below 5,000 feet elevation.
It tolerates high salt content and high water temperatures.
 It was once common in desert springs, marshes, backwaters, and tributaries
of the Rio Sonoyta, lower Gila River, and lower Colorado River drainages
in Arizona, California, and Mexico. Three natural populations of pupfish
exist in Imperial and Riverside Counties, California. No naturally occurring
populations remain in Arizona. Natural populations survive in four locations
in the Colorado River delta, Sonora and Baja California, Mexico, and in
the Rio Sonoyta in Sonora, Mexico. Introduced populations now exist in
small springs, streams, and ponds in Imperial, Riverside, and Butte Counties,
California, and in Pima, Pinal, Maricopa, Graham, Cochise, La Paz, and
Yavapai Counties, Arizona.
Desert pupfish declined due to the introduction and spread of exotic predatory
and competitive fishes, water impoundment and diversion, water pollution,
groundwater pumping, stream channelization, and habitat modification.
In the Salton Sea, desert pupfish are the only native fish species. They
can be found in shoreline pools, agricultural drains, natural creeks and
a few artificial refuge ponds. The actual use of the Sea itself by the
desert pupfish is largely unknown. The protection and enhancement of existing
habitats including shoreline pools, agricultural drains and natural creeks
in the Salton Sea watershed are necessary for the future of this species
in California.
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Yuma clapper rail (Rallus longirostris
yumanensis):
The Salton Sea currently supports an estimated 40% of the entire U.S.
population of this species. Due to the large percentage of this species
using the habitats of the Salton Sea area, actions to preserve and increase
fresh water marsh habitat may play a vital role in the recovery of the
Yuma clapper rail. With decreasing water inflows to the Sea from water
conservation and water transfers, marsh habitat for this species is expected
to dec rease.
The Yuma clapper rail was listed on the Endangered Species List on March
11, 1967. The disappearance of suitable habitat for this species has had
the most direct impact on their declining numbers, although pollution
has also contributed. Primarily, human-related modifications of wetland
habitat, such as channelization, bank stabilization, and water impoundments
have had the greatest impact. Furthermore, rail's prey upon crayfish,
which are vulnerable to pesticides and heavy metal poisoning.
At the Sonny Bono Salton Sea National Wildlife Refuge, significant populations
of Yuma clapper rails nest in the fresh water marshes maintained by the
refuge. Water control projects on the Colorado River have built dams which
altered the nature of this free-flowing body of water. Some backwaters
were eliminated, but the dams created much new habitat for the birds by
allowing sedimentation, which in turn allowed cattail and bulrush marshes
to emerge. However, other suitable rail habitat has been lost through
dredging and channelization projects along the Colorado River. In addition,
the Salton Sea, while providing a significant amount of habitat, is becoming
very salty. Regular outbreaks of botulism there have killed numerous birds,
including rails.
Although the rail population appears stable, there is no denial that its
fate is directly related to the various water projects along the Colorado
River. It is clear that the key to preserving the Yuma clapper rail is
the maintenance of early growth stages of cattail marsh by creating shallow
water areas. The mats of dead cattails in the shallows will eventually
provide nesting cover for the rails.
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California Bird Species of Special Concern
Burrowing owl (Athene cunicularia):
Burrowing owls were at one time fairly common and widespread over western
North America. Populations have declined and in some cases have disappeared
due to the large scale changes that humans have made to the owls habitat.
They are listed as endangered or threatened in a number of states and
are endangered in Canada. Burrowing owls are now federally listed as a
Species of Management Concern and are a Species of Special Concern in
California. The populations of burrowing owls in the Imperial Valley are
year-round residents, unlike many populations that are migratory. The
Imperial Valley also has the largest population of burrowing owls in the
state of California - it is estimated that 70-80 percent of burrowing
owls found in California reside in Imperial County.
Burrowing owls nest in vacated burrows made by mammals such as ground
squirrels or similar holes in the ground. Nest burrows are very distinctive
because the owls line the entrance with material such as cow-manure, insect
parts, cotton, dead toads, plastic and tin foil. Burrowing owls are diurnal,
meaning they are active day and night. Most of them search for prey during
the night. Prey items include mammals, birds, reptiles, amphibians, insects,
spiders, centipedes, scorpions, crayfish, and mollusks.
In the Imperial Valley burrowing owls can most often be seen along irrigation
drains, canals, and delivery ditches. The Imperial Irrigation District
searches for owl burrows before any concrete canal lining projects are
started. If owls are found nesting within an area that may be affected
by such a project, construction is delayed until the young have left the
burrow. There is currently a statewide census of burrowing owls that has
helped to determine if owl populations are reaching an endangered status.
The census studied owl breeding patterns and provided critical information
for plans to protect them.
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California
brown pelican (Pelecanus occidentalis):
The Salton Sea currently supports a year round population of California
brown pelicans. Peak numbers can reach 5,000 individuals. This species
nested successfully at the Salton Sea (first nesting of a CA brown pelican
on an inland lake) in 1996 and has attempted nesting since then.
Mexican and United States biologists feel the Salton Sea may prove to
be important in the recovery of this endangered species and has proven
to be important to the Sea of Cortez population for range expansion. Ensuring
open water (fresh and salt), a food resource and islands for roosting
and nesting are critical for this species.
The California brown pelican was listed on the Endangered Species List
on June 2, 1970. The primary reason for its decline was the use of DDT
and polychlorinated biphenyls, which resulted in thin-shelled eggs that
were easily broken during incubation or another impairment of reproductive
success. The Environmental Protection Agency banned the use of DDT in
1972 and has also restricted use of edrin, a type of polychlorinated biphenyl
related to brown pelican declines. Since that time the nesting success
has risen as the levels of these compounds have decreased in most areas.
California brown pelicans at the
Salton Sea are sometimes afflicted with botulism, which is caused by eating
fish that also carry the disease.
Botulism paralyzes the muscles of diseased birds, which is eventually
fatal. U.S. Fish and Wildlife staff at the Sonny Bono Salton Sea National
Wildlife Refuge conduct air boat surveys of the Sea during botulism outbreaks,
collecting dead and sick birds. Pelicans in the early stages of botulism
are sent to rehabilitation centers, where they are cared for and later
released. For more information, see our wildlife
disease page.
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Mountain plover (Charadrius montanus):
In 1999, the mountain plover was proposed as a threatened species on the
Endangered Species List. This means that the Fish and Wildlife Service,
after thoroughly examining the best scientific information available,
believes that the mountain plover is likely to become endangered in the
foreseeable future throughout all or a significant potion of its range
unless actions are taken now to reverse the decline in population. The
mountain plover is important because it, and other native species, are
indicators of the health of native prairies. The decline of the mountain
plover is an early warning that the replacement of many native grasslands
with urban development or grazing and farming practices, are hindering
the survival of the short-grass prairie.
The decline in the mountain plover population is due to a combination
of factors - native grasslands being replaced by agriculture and urban
development; early spring plowing and planting on dryland nesting sites;
and loss of prairies dogs and other burrowing rodents. Mountain plovers
are commonly found attempting to breed on plowed land in several states,
however surveys have found that successful nesting is interrupted by subsequent
planting and crop growing before nesting is complete. In addition, livestock
grazing practices that encourage taller grasses and forbs eliminate mountain
plover habitat.
The Imperial Valley has one of the largest wintering populations of this
species in the Pacific Flyway with 1,000 to 1,500 typically in the Valley.
The species is migratory, spending winters in the south-western U.S. and
Mexico and summer at their breeding grounds further north in suitable
short-grass prairie habitat. Mountain plovers are gregarious during the
winter, and can be seen in grassy or bare soil fields.
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Birds of Interest
American white pelican (Pelecanus
erythrorhynchos):
This species is both migratory and resident at the Salton Sea. Peak numbers
of white pelicans using the Sea have been recently estimated at 26,000
during spring migration. This is thought to comprise between 80 and 90%
of the entire
Western population of American white pelicans. The Salton Sea provides
a vital link in the migratory path of this species on the Pacific Flyway.
The longest migratory jump for white pelicans on the flyway is between
the Salton Sea and the Central Valley. Without the resources of the Salton
Sea, white pelicans would be forced to fly even further to rest and forage
during migration.
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Black skimmer (Rynchops niger):
Black skimmers are common at the Salton Sea during the breeding season
(in the summer months), and several hundred nesting pairs have been recorded
in previous years, representing the largest population of black skimmers
in Western North America. Black skimmers are unique in that their bill
(consisting of an upper and lower mandible) is unlike any other bird. The lower mandible is longer than the upper mandible. This
is an adaptation to the feeding method used by the black skimmer: while
foraging, they fly with their lower mandible slicing through the water,
catching crustaceans and other prey items. The lower mandible would be
quickly eroded away by friction if it did not grow roughly twice as fast
as the upper mandible. Skimmers in zoos, deprived of the opportunity to
skim, soon have lower mandibles much, much longer than the upper.
Black skimmers winter in South America, as far south as southern Chile
and central Argentina. Millinery trade in the past targeted skimmers for
their feathers, which were used in hat decorations, and eggs were also
taken by humans. Even slight human disturbance at a nesting colony can
reduce the reproductive success.
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Eared grebe (Podiceps nigricollis):
The Salton Sea is the wintering destination and migratory stop over for
up to 1 million eared grebes, approximately 95% of the continental population
for this species. This species typically migrates through Mono Lake and
Salt Lake to the Salton Sea and seems to prefer the saline lake environments.
Without the Salton Sea, eared grebes normally wintering at the Sea would
be forced to migrate to the Sea of Cortez.
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Peregrine falcon (Falco peregrinus):
Peregrine falcons were at one time common in parts of the Appalachian
Mountains and nearby valleys from New England south to Georgia, the upper
Mississippi River Valley, and the Rocky Mountains. They also inhabited
mountain ranges and islands along the Pacific Coast from Mexico north
to Alaska and in the Arctic tundra. Beginning in the late 1940s, peregrine
falcons suffered a devastating and rapid decline. By the mid-1960s, the
species had been eliminated from nearly all of the eastern U.S. Although
less severe, the decline spread west, where peregrine populations were
reduced by 80 to 90 percent by the mid-1970s.
The cause of the decline in the population was due to unusually high concentrations
of the pesticide DDT and its breakdown product DDE in peregrine falcons
and other birds of prey. The peregrine accumulated DDT in their tissues
by feeding on birds that had eaten DDT-contaminated insects or seeds.
The toxic chemical interfered with eggshell formation. As a result, falcons
laid eggs with shells so thin they often broke during incubation or otherwise
failed to hatch. Because too few young were raised to replace adults that
died, peregrine populations declined precipitously. The falcon was listed
as endangered in 1970. In 1972 the EPA banned DDT for most uses in the
U.S. The reduction in DDT use as well as the reintroduction of peregrine
falcons throughout the U.S. has helped the population rebound. Populations
are now estimated at 1,650 breeding pairs in the U.S. and Canada, with
additional birds in Mexico. In August 1999, the U.S. Fish and Wildlife
Service removed the peregrine falcon from the list of endangered and threatened
species, marking one of the most dramatic successes of the Endangered
Species Act.
At the Salton Sea, peregrines can be seen frequently. Several pairs have
nested at the Sonny Bono Salton Sea National Wildlife Refuge. The future
of the species is still dependent on the continued ban of DDT and other
similar pesticides.
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Ruddy ducks (Oxyura jamaicensis):
The Salton Sea provides wintering habitat for an estimated 50% of the
total number of ruddy ducks found in the Pacific Flyway. Future wetland
loss and habitat degradation may increase the importance of the Salton
Sea to this species. Protecting open water habitat and food resources
are important to maintaining this species at the Salton Sea.
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Yellow-footed gull (Larus livens):
The yellow-footed gull is a fairly common visitor to the Salton Sea -
which is one of the only places in the United States that this species
can be seen. The gulls breed in the Gulf of California, and can be seen
after this period at the Salton Sea. A few usually linger at the Sea into
winter, and they are very rare in spring. They can also be found occasionally
on the coast of southern California.
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Shorebirds:
The Salton Sea has been designated as an internationally important staging
area for shorebirds. Over 124,000 shorebirds of at least 25 species migrate
through the Salton Sea along the Pacific Flyway. It is considered the
third most important shorebird habitat west of the Rocky Mountains. Several
species rely heavily on the Salton  Sea
to support a large portion of their flyway population including:
1. Western sandpipers (Calidris mauri) (54,000)
2. American avocet (Recurvirostra americana) (19,000)
3. Dowitcher spp. (Limnodromus spp.) (12,000)
4. Red-necked phalarope (Phalaropus lobatus) (12,000)
5. Whimbrel (Numenius phaeopus) (9,800)
6. Black-necked stilt (Himantopus mexicanus) (10,000)
In addition the Salton Sea supports the greatest number of Western snowy
plovers in the interior of California. Coastal populations of this species
are listed as Federally Threatened. The Salton Sea could play an important
role in the future for snowy plover populations.
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