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

SECOND NORTH AMERICAN SEA DUCK CONFERENCE
PRELIMINARY CHARACTERIZATION OF MIGRATION AND BREEDING GROUNDS
ASSOCIATED WITH WHITE-WINGED SCOTERS WINTERING IN
WASHINGTON STATE FROM ONGOING TRACKING
OF SATELLITE TRANSMITTERS
Joseph R. Evenson, David R. Nysewander, Bryan L. Murphie, Thomas A. Cyra, Briggs Hall,
Dyanna Lambourn, Don Kraege, Daniel Esler, and Sean Boyd.
Washington Department of Fish & Wildlife; evensjre@dfw.wa.gov
A number of marine birds and sea ducks have experienced significant declines in numbers over the
last 25 years in the marine waters of Washington State, with scoters composing one of the larger avian
biomasses associated with this decline. However, little was known until recently of movements and
population demography of either of the two more numerous wintering scoter species populations, the
surf scoter (Melanitta perspicillata) and the white-winged scoter (Melanitta fusca), on the west coast
and how they might relate to each other. The white-winged scoter makes up roughly 35% of the scoters
found in Washington during the winter on average. Focus studies started in 2003 on both species, but
the effort devoted to white-winged scoters involved implanting them with only satellite transmitters.
Our first source of outside funding directed us to look at this species, so as to complement an
ongoing similar effort by scientists in the Strait of Georgia that was looking at white-winged scoters.
These initial studies are scheduled to continue until 2006 in Washington using satellite transmitters
primarily for the purpose of documenting the patterns of distribution and fidelity to winter and spring
foraging areas, night concentrations, migration routes, range of breeding sites, and molting areas of
those adult scoters wintering in Washington. Between years wintering site fidelity was examined to
determine what proportion of white-winged scoters return to the marine waters of Washington, and
if white-winged scoters captured in British Columbia come to Washington the winter after capture,
instead of returning to the region of capture. Though the sample size is relatively small, we wanted to
evaluate if immigration/ emigration between years occurs. We also compare scoter population trends
from the USFWS and CWS Waterfowl Breeding Population and Habitat Survey, from the strata in
the Canadian interior where Washington scoters breed, with wintering trends from Washington State.
Three years of the project have now been completed, suggesting confirmation of the following: 1)
Distinct differences in distribution and movement exist between the two main scoter species, between
male and female scoters within each species, and even some suggestions of differences between
different but close flyway subpopulations of white-winged scoters, such as those from the Strait of
Georgia and Puget Sound. 2) The time spent by scoters in marine areas is considerable, with 9-10
months for males and 8-9 for females observed, often including molting flightless periods in western
Washington in late summer. 3) western Washington contains important wintering and spring staging
areas used by white-winged scoters as well as summer molting areas. 4) These staging areas were
often different than those used by surf scoters. These Washington spring staging areas also attract a
certain proportion of British Columbia white-winged scoters. 5) The white-winged scoters we tracked
tended to return daily and yearly often to the same locations, expressing considerable site fidelity.
82 ANNAPOLIS, MARYLAND, USA NOV. 7-11, 2005