White-winged, Black and Surf Scoter Habitat
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Surf scoter (Melanitta perspicillata), black scoter (Melanitta nigra), and white-winged scoter (Melanitta fusca). Inventories showed populations of all 3 scoter species declined in the period 1954 to 1994 (Kehoe et al. 1994). Because all 3 winter in the study area, have similar feeding habits, and often are grouped in winter surveys, a single model was developed for all three species.
Use of Study Area Resources:
Wintering. Surf scoters and white-winged scoters breed in northwest and north-central Canada (Savard et al. 1998). Black scoters breed in western Alaska. Along the Atlantic coast, North America populations winter from Newfoundland to Florida (Palmer 1975, Savard et al. 1998). Maine sea duck harvest data show largest numbers are surf, followed by white-winged, then black scoters (MDIFW www page).
Food resources. In the Northeast, highest densities of scoters occur in areas of abundant, preferred foods (Cottam 1939, Stott and Olson 1973, Vermeer and Bourne 1982). In coastal areas, animal foods make up most (> 80%) of their diet, primarily molluscs and crustaceans (Cottam 1939, Brown and Fredrickson 1997). Blue mussels and short yoldia (Yoldia sapotilla) were the most important foods of birds collected in Massachusetts, while Atlantic razor clams (Siliqua spp.) were the most important food for birds collected in Long Island Sound (McGilvrey 1967). Arctic wedge clam (Mesodesma arctatus), Atlantic razor clam, and blue mussel accounted for the majority of food volume for scoters collected along the New Hampshire and Massachusetts coasts (Stott and Olson 1973). Arctic wedge clams and Atlantic razor clams occur in sandy substrates along these coastlines (Stott and Olson 1973). Scoters feed in open water, including the regularly flooded portions of the intertidal zone, and subtidal areas (Vermeer and Bourne 1982, Bordage and Savard 1995).
Cover. Along New Hampshire and Massachusetts coastlines scoters prefer sandy beaches to rocky headlands (Stott and Olson 1973), although they are found off rocky shores on the west coast of North America (Savard et al. 1998) and Newfoundland (Goudie 1984). Scoter foraging depth is usually < 10 m (Cottam 1939, Vermeer and Bourne 1982, Sanger and Jones 1984, Bordage and Savard 1995, Goudie et al. 1994 in Savard et al. 1998).
Habitat suitability for these species is scored according the likelihood of use by any of the 3 scoters. Habitat was mapped using distribution information on scoter food resources (shellfish), supplemented with known scoter occurrence locations. Data on shellfish availability that was regarded as of a 'general' nature was used to map "potential foraging habitat"; more specific information on suitable shellfish beds was used to map "apparent foraging habitat". The latter, by implying a higher likelihood of suitable conditions, was assigned higher scores.
"Potential foraging habitat" was identified as relatively shallow (lower-intertidal to < -10 m) marine and estuarine areas either 1) having sandy substrates that are associated with occurrences of Atlantic razor clam and Arctic wedge clam, or 2) within the relatively large coastal segments of the NOAA 1995 National Shellfish Register. Substrate data was derived from Banner and Hayes (1996), Barnhardt et al. (1996), Knebel and Circe (1995), Brown et al. (in press) and Butman and Lindsay (1999). The NOAA 1995 National Shellfish Register coverage, characterizing general shellfish growing areas by state, was provided by Kenneth Buja, NOAA SEA Division.
"Apparent foraging habitat" was mapped as waters in the lower-intertidal to < -10 m depth range and having mapped concentrations of blue mussels or other shellfish. Beds of a variety of bivalve molluscs were identified using previously developed data for coastal New Hampshire (Banner and Hayes 1996) and a Maine DMR shellfish coverage (provided by Seth Barker, MEDMR).
Available occurrence information included the data from annual USFWS mid-winter waterfowl surveys (general abundance, polygon data), 1985 through 1999. These were processed by taking the maximum counts per segment polygon (or sub-segment, where available), and calculating nominal number of birds per unit area. Data from a second source, Maine's Coastal Wildlife Concentration Areas (Maine Department of Inland Fisheries and Wildlife) counts, were similarly used to calculate birds per unit area.
"Potential foraging habitat" was scored as 0.3 on a 0 to 1.0 scale. "Apparent foraging habitat" was scored 0.5. Where these foraging habitats coincided with the occurrence of one or more scoters per 10 ha from either of the above survey data sets, they were scored 0.6 and 1.0, respectively. Areas having scoters and suitable depth, but without indications of shellfish beds were scored 0.5 (see table, below).
SUITABILITY SCORING (scale 0 - 1.0)
|scoter abundance:||forage not documented||apparent foraging habitat||potential foraging habitat|
Model Testing: The specific scoter occurrences (point data) from the Winter Waterfowl Surveys for 1999 and 2000 in Maine were used to test the habitat map. We drew a bounding polygon encompassing all waterfowl observations for those surveys, and used a random point coverage which had 70 points within the bounding polygon. We then compared the presence of habitat near the random points to that for sites at which scoters were observed. Of the 349 sites with scoters, 261 had mapped habitat, while only 24 out of the 70 randomly distributed sites had habitat. The Chi-square was highly significant, indicating that the overall model does indicate localities useful to scoters.
Banner, A. and G. Hayes. 1996. Important Habitats of Coastal New Hampshire. USFWS Gulf of Maine Project, Falmouth, ME. 77 p.
Barnhardt, W.A., D.F. Belknap, A.R. Kelley, J.T. Kelley and S.M. Dickson. 1996. Surficial Geology of the Maine Inner Continental Shelf. Digital Data provided through Maine Office of GIS.
Bordage, D. and J.L. Savard. 1995. Black scoter (Melanitta nigra). In The Birds of North America, No. 177 (A. Poole and F. Gill, eds.). the Academy of Natural Sciences, Philadelphia, and The American Ornithologists' Union, Washington, D.C.
Brown, S.K., K.R. Buja, S.H. Jury, M.E. Monaco,and A. Banner. In press. Habitat Suitability Index Models for Casco and Sheepscot Bays, Maine. Silver Springs: MD NOAA/SEA DIVISION, and Falmouth, ME: USFWS. 86 pp.
Brown, P. W. and L. H. Fredrickson. 1997. White-winged Scoter (Melanitta fusca). In The Birds of North America, No. 274 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D.C.
Butman, B. and J.A. Lindsay. 1999. A Marine GIS Library for Massachusetts Bay Focusing on Disposal Sites, Contaminated Sediments, and Sea Floor Mapping. U.S. Geological Survey Open-File Report 99-439. September 1999. U.S. Geological Survey, Woods Hole, MA and NOAA Office of Response and Restoration, Seattle, WA.
Cottam, C. 1939. Food habits of North American diving ducks. U.S. Dep. Agric. Tech. Bull. 643:121-139. Washington DC.
Goudie, R.I. 1984. Comparative ecology of common eiders, black scoters, oldsquaws, and harlequin ducks wintering in southeastern Newfoundland. M.S. Thesis, Univ. Western Ontario, London, ON. 137 pp.
Kehoe, F.P., D. Caithamer, J. Myers, R. Burrell and B. Allen. 1994. Status of sea ducks in the Atlantic Flyway with strategies towards improved management. Ad Hoc Sea Duck Committee, Atlantic Flyway Technical Section.
Knebel, H.J. and R.D. Circe. 1995. Maps and diagrams showing acoustic and textural characteristics and distribution of bottom sedimentary environments, Boston harbor and Massachusetts Bay. Misc. Field Studies Map, USGS. Map MF-2280.
McGilvrey, F. B. 1967. Food habits of sea ducks from the northeastern United States. Wildfowl Trust Ann. Rep. 18:142-145.
MDIFW (Maine Department of Inland Fisheries and Wildlife). Waterfowl Populations. http://www.state.me.us/ifw/wildlife/wpr/duck.htm downloaded 6/22/01.
Palmer, R.S. 1975. Handbook of North American Birds. Yale Univ. Press, New Haven, CT.
Sanger, G.A. and R.D. Jones, Jr. 1984. Winter feeding ecology and trophic relationships of oldsquaws and white-winged scoters on Kachemak Bay, Alaska. Pp. 20-28 in Marine birds: their feeding ecology and commercial fisheries relationships (D. N. Nettleship, G.A. Sanger, and P.F. Springer, eds.). Proc. of Pacific Seabird Group Symposium, Seattle, Washington, 6-8 Jan, 1982. Can. Wildl. Serv., Ottawa, ON.
Savard, J.L., D. Bordage and A. Reed. 1998. Surf Scoter (Melanitta perspicillata). In The Birds of North America, No. 363 (A. Poole and F. Gill eds.). The Birds of North America Inc., Philadelphia, PA.
Stott, R.S. and D.P. Olson. 1973. Food-habitat relationship of sea ducks on the New Hampshire coastline. Ecology 54: 996-1007.
Vermeer, K. and N. Bourne. 1982. The white-winged scoter diet in British Columbia waters: resource partitioning with other scoters. Pp. 30-38 in Marine birds: their feeding ecology and commercial fisheries relationships (D. N. Nettleship, G. A. Sanger, and P. F. Springer, eds.). Proc. of Pacific Seabird Group Symposium, Seattle, WA, 6-8 Jan, 1982. Can. Wildl. Serv., Ottawa, ON.