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

SECOND NORTH AMERICAN SEA DUCK CONFERENCE
FACTORS AFFECTING, AND CONSEQUENCES OF, MALE ATTENDANCE AT A
COMMON EIDER COLONY IN THE CANADIAN ARCTIC
Kerrith McKay¹, H. Grant Gilchrist², and Tom D. Nudds³
¹University of Guelph and Canadian Wildlife Service; kmckay@uoguelph.ca
²Canadian Wildlife Service, National Wildlife Research Centre, Carelton University
³Zoology Department, University of Guelph
Typically, male sea ducks follow females to breeding grounds where they guard their mates against
extra pair copulations (EPC), although they rarely follow females directly to nests. However, among
common eiders (Somateria mollissima), there is considerable variation in male attendance of
females at nests; both between and within colonies. Why does this variation exist, and what do male
common eiders gain by attending colonies? Previously, we found that males rarely attend females
onto colonies under conditions where there are resident mammalian predators and/or vegetation that
confers an advantage to a predator (McKay et al. submitted a). On colonies where males do attend
females, we predicted that nest attendance by males may increase their annual reproductive success
by, 1) contributing directly to nest site selection and hatching success, 2) protecting their paternity by
defending their female against extra-pair copulations, and/or 3) by attempting EPCs themselves while
in close proximity to other females on the colony. At a large eider colony near Southampton Island
in the Canadian Arctic, we found that males did not participate in nest site selection or nest defense,
nor did the duration of their attendance affect the number of eggs that hatched successfully (McKay
et al. submitted b). We also collected observational data from over 1000 nests, between 2000-2003, to
determine whether the duration of male nest attendance varied within the colony in relation to nesting
density, yearly variation, and the laying phenology of females. We found that the average length of
male attendance differed significantly between years and declined as the breeding season progressed.
Small differences were also detected between observation plots, suggesting that the duration of male
attendance was longer in areas of high nesting densities where the potential of EPCs was greatest.
We also observed eider pairs interacting on the colony to determine if unattended females were more
likely involved in aggressive interactions with lone males than pairs. Preliminary results follow
predictions, where unattended females suffered more aggressive interactions with prospecting (lone)
males whether walking or incubating, and that these interactions were greatest in areas of high nesting
densities. To examine the behavioral ecology of male colony attendance, we recognized the need to
acquire molecular evidence of extra pair paternity between nests with and without male attendance. We
examined this by experimentally removing attending males from a random selection of eider nests in
2002 and 2003, to determine if male removal lowered the probability of hatch, while simultaneously
increasing extra-pair paternity. We predicted that paired (control) females would experience greater
reproductive success than experimentally widowed females, and that the paternity of eggs (no. of
fathers) would increase among widowed birds. Results of this genetic analysis are ongoing, and will
be discussed.
98 ANNAPOLIS, MARYLAND, USA NOV. 7-11, 2005