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

SECOND NORTH AMERICAN SEA DUCK CONFERENCE
PACIFIC COMMON AND KING EIDER SPRING MIGRATION, SITE FIDELITY
AND POPULATION STRUCTURE: INSIGHTS GAINED FROM LONGER-LASTING
SATELLITE TRANSMITTERS
Lynne Dickson¹, Tim Bowman², Andrea Hoover,¹ and Garnet Raven¹
¹Canadian Wildlife Service, Room 200, 4999-98 Ave., Edmonton, Alberta, Canada T6B 2X3;
lynne.dickson@ec.gc.ca
²USFWS, 1011 East Tudor Road, Anchorage, Alaska, USA, 99503
Satellite transmitters deployed on Pacific common (Somateria mollissima) and king eiders (Somateria
spectabilis) on their breeding grounds in central arctic Canada in June 2003 lasted nearly twice as
long on average as transmitters we had deployed in the previous six years. Nearly all transmitters from
earlier years ceased functioning by the end of winter, whereas 21 of 28 transmitters deployed in 2003
lasted several more months, thus providing new information on timing and routes of spring migration,
nesting and molting site fidelity, and population structure. For both species, all females returned to the
same nesting area as in the previous year (n=9), whereas males all migrated to different locations to
breed (n=11). However, despite breeding in a different area, 7 of 8 males returned to the same postbreeding
molting area as in the previous year. In all years, we found that both male and female Pacific
common eiders wintered in the same area off the southeastern Chukotsk Peninsula and St Lawrence
Island. Therefore, the wide distribution of males during the second nesting season suggests that this
wintering area is critical for Pacific common eiders throughout their entire breeding range in arctic
Canada and northern Alaska. Spring migration occurred over a two-month period from mid April
to mid June. Key staging areas for both species were Ledyard Bay and the polynia in southeastern
Beaufort Sea. Daily locations obtained for six Pacific common eiders indicated birds heading for
Canada to nest followed the shorefast ice edge rather than the Alaskan coast. They crossed the Alaskan
Beaufort Sea in less than a day, although all but one stopped briefly at least once on the way. These data
on spring migration have provided a better understanding of vulnerability of eiders to offshore oil and
gas development in the Beaufort Sea.
NOV. 7-11, 2005 ANNAPOLIS, MARYLAND, USA
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