Second North American Sea Duck Conference - Patuxent Wildlife ...

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SECOND NORTH AMERICAN SEA DUCK CONFERENCE POPULATION DYNAMICS OF MERGANSERS: INFERENCES FROM HISTORIC AND CONTEMPORARY DATA SETS John Pearce¹, Paul Flint, ¹ and Mark Lindberg² ¹USGS, Alaska Science Center; John_Pearce@usgs.gov ²Department of Biology and Wildlife, University of Alaska, Fairbanks As with eider and scoter populations 10 years ago, little is known about the habits and ecology of common (Mergus merganser), red-breasted (M. serrator), and hooded mergansers (M. cucullatus). While North American trend data suggests that all three merganser species are stable, if not increasing at the continental scale, our understanding of these trends and their relation to regional scale population demography is limited. Breeding and wintering distributions of all three species differ markedly across North America, likely because of species-specific nesting habits, rates of dispersal, and responses to the most recent retreat of Holarctic glaciers 20,000 years ago. As a result, regional populations, such as the Great Lakes or south-central Alaska, may differ demographically and genetically. We used both historic (genetic) and more contemporary (mark-recapture) data collected from across North America for common and hooded mergansers. Samples were collected from across North America and screened for variation using primers that amplify domain I of the control region of mitochondrial (mt) DNA. Band recovery information was obtained from both U.S. and Canadian banders. Estimates of annual survival and recovery rates by region were summarized using Program MARK. Locations of band recoveries were plotted on maps. Initial analyses indicate geographic variation in survival and migratory tendency for available banding data. Surprisingly, band recovery rates for common mergansers were as high as documented for some species of dabbling ducks. Genetic analyses provide information on both population differentiation and historical demographic patterns. We argue that the combination of demography and genetics allows greater inference into patterns of gene flow and demography. 24 ANNAPOLIS, MARYLAND, USA NOV. 7-11, 2005
John Reed and Paul L. Flint SECOND NORTH AMERICAN SEA DUCK CONFERENCE LIMITED FIDELITY IN HARLEQUIN DUCKS WINTERING NEAR DUTCH HARBOR, ALEUTIAN ISLANDS, ALASKA USGS - Alaska Science Center; john_reed@usgs.gov Dutch Harbor, on Unalaska Island, is the hub for Berring Sea and northern Gulf of Alaska fisheries and is the busiest fishing port in the United States. From November through April large concentrations of sea birds and sea ducks (including Steller’s eiders (Polysticta stelleri), long-tailed ducks (Clangula hyemalis), black (Melanitta nigra) and white-winged (Mulanitta fusca) scoters, and harlequin ducks (Histrionicus histrionicus) ) use the waters around Dutch Harbor. During the winters 2001-2005 we used floating mistnet sets to capture harlequin ducks at five sites near Dutch Harbor. In 2004, we fitted 32 harlequin ducks with VHS transmitters and used triangulation to follow their local movements several times daily during February - March. From a total of 373 captures across years, only 6 (1.6 %) were ever recaptured and only 4 were recaptured across years. We used 2004 telemetry data to calculate movement probabilities among broad area classifications. Twelve of our radio transmittered birds died (≥6), lost their radios (≥1), and/or emigrated and were not included in our analyses of fidelity. We used multistate mark-recapture models to estimate the transition probabilities among areas. The probability of moving between sites on sequential days ranged from 0-0.47 and the probability of using multiple sites within a single day was 0.32. Only four birds used one site exclusively through the tracking period. The mean minimum convex polygon home range was 326.5 ha (56.2 s.e.). This mean home range size may be underestimated if birds also used areas outside the range of our tracking antennas. Our results are in contrast to other studies in Prince William Sound, Alaska and British Columbia where within and across year fidelity to specific sites has been a hallmark of wintering harlequin ducks. In those studies marked birds were consistently resighted within years and recaptured across years along the same few kilometers of coastline. Reasons for these differences may be related to: intra-specific competition, the distribution of food relative to predation pressure, and inconsistent or patchily distributed food supply. NOV. 7-11, 2005 ANNAPOLIS, MARYLAND, USA 25
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