Graduate Research Fellow - Eric Anderson
NOAA/Padilla Bay NERR Graduate Research Fellow
Habitat for Scoters
Eric Anderson
Ph.D. Candidate, University of Wyoming
Department of Zoology and Physiology
Laramie, WY
Relative roles of eelgrass vs. hard-mixed substrates as habitatfor scoters (Melanitta spp.) in Puget Sound
BACKGROUND
Scoters ( Melanitta spp. ) are sea ducks that breed in freshwater
wetlands of Canada and Alaska and winter in estuaries and bays on the Pacific and
Atlantic coasts (Fig. 1). As with most sea ducks, scoter populations have
declined in many parts of their Pacific Coast ranges. Three species of scoter can
be found in wintering in Puget Sound, the common scoter ( Melanitta nigra ),
the white-winged scoter ( Melanitta deglandi ) and the surf scoter ( Melanitta
perspicillata ). The combined population of all three scoters declined
by 57% between 1978-79 and 1992-99. Scoter habitat-use patterns, particularly in soft-bottom
eelgrass ( Zostera spp.) beds are insufficiently characterized to identify if and
how changes in habitat are affecting scoters.
Fig. 1. White-winged scoter. Scoters winter
on the Pacific and Atlantic coasts of North America.
Scoters are diving ducks and depend on availability of food sources on the sediment surface for food. Several factors suggest that scoter foraging profitability is greater in hard-mixed substrates than in soft-bottom eelgrass beds in early to mid-winter, but shifts in favor of eelgrass habitat in later winter. This conjecture is reflected by the location of the scoters throughout the winter. During early to mid-winter, scoter densities are greater in areas of hard-mixed substrate than in eelgrass beds. In late winter, substantial scoter populations arrive in Padilla Bay, which has one of the largest eelgrass beds on the Pacific Coast (Fig. 2). While the exact reason for this move is not known, large flocks of wintering sea ducks are known to deplete mussels seasonally in hard-mixed substrates. Thus, large eelgrass beds, such in Padilla Bay, may be important to sustaining regional scoter populations through the late winter and early spring.
To identify mechanisms sustaining diving duck populations within estuarine ecosystems, this research will (1) compare seasonal changes in scoter prey depletion, foraging parameters, and scoter distributions at two research areas, one with a hard-mixed substrate (Penn Cove), and one with soft-bottom eelgrass beds (Padilla Bay) and (2) examine a possible shift of scoter foraging profitability from hard-mixed substrate in mid-winter to soft-bottom eelgrass habitat in late winter to early spring.
Fig. 2. Large flock of scoters as seen in a spotting scope.
METHODS
Eric is investigating differences between hard-mixed substrate in Penn Cover and soft-bottom
eelgrass habitat in Padilla Bay. He is relating seasonal shifts in regional scoter distributions to
habitat types and herring spawning events using GIS. Scoter habitat is being characterized by
measuring elevation, wave exposure, and tidal channel parameters.
Eric is using diet analysis of scoter esophagus contents, stable isotope analysis and fatty acids to compare habitat use of surf scoters in the two communities (Fig. 3).
Scoters and other sea ducks vary in foraging locations, time spent foraging, and prey selection within tidal, dial, and seasonal cycles. Frequent observations of scoter location and behavior will allow Eric to map scoter distributions and foraging parameters. Infaunal and epifaunal invertebrates will be sampled to document prey availability. Seasonal comparisons of prey density and bioenergetics models will be used to evaluate prey depletion by scoters.
An additional benefit of this research is the opportunity to document seasonal distributions of other diving birds in Padilla Bay.
Fig. 3. Field crew gathering data for diet analysis.
MANAGEMENT IMPLICATIONS
Clarification of mechanisms sustaining diving duck resources within Padilla Bay will
assist in habitat conservation and restoration recommendations. Information gained from
this research will clarify linkages between scoter populations and conditions in nearshore
habitats. This research will also initiate a synthesis of regional scoter habitat requirements.
Fig. 4. Eric Anderson and a surf scoter.
BIOGRAPHICAL INFORMATION
Eric is a PhD candidate in the Department of Zoology and Physiology at the University of Wyoming (Fig. 4). His graduate advisor is Dr. James Lovvorn in the Department of Zoology and Physiology at the University of Wyoming. Eric received his M.S. in Zoology and Physiology from the University of Wyoming, and his B.S. in Mathematics and Biology from the University of Puget Sound. Eric's research is partially funded by a Padilla Bay NERR Graduate Research Fellowship.