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

SECOND NORTH AMERICAN SEA DUCK CONFERENCE
MALE ATTENDANCE AT COMMON EIDER COLONIES:
A CIRCUMPOLAR REVIEW
Kerrith McKay, H. Grant Gilchrist, and Tom D. Nudds
Canadian Wildlife Service, National Wildlife Research Centre, Carelton University,
and, Zoology Department, University of Guelph; kmckay@uoguelph.ca
A species may have the genetic potential for specific traits but not exhibit them, suggesting that certain
phylogenetic traits are constrained by environmental factors such as weather, habitat, conspecifics,
or predators. It is often difficult to elucidate factors that may constrain individuals, populations or
species, because it is rare to find behavioral variation within a species across its range necessary
to identify specific environmental factors that influence these behavioral traits. The common eider,
(Somateria mollissima), is a colonial-nesting seaduck that inhabits both polar and temperate regions
of the northern hemisphere. At some locations, males venture onto island colonies and attend nesting
females, whereas at other colonies they do not. By visiting colonies, male eiders could enhance their
annual reproduction by: i) guarding their mates against extra pair copulations (EPCs); ii) contributing
to parental care that could enhance the survival of their own eggs and ducklings; and iii) by gaining
EPCs while in close proximity to other nesting females; and these potential benefits are not mutually
exclusive. However, there are also costs associated with coming onto land including lost feeding
opportunities at sea and potentially higher mortality risks (e.g. particularly due to mammalian
predation). Thus, a trade-off may exist between the benefits of colony attendance (parental care,
mate-guarding) and the costs of doing so (mortality risk and lost feeding opportunities), and an
examination of how male behaviors vary regionally could help identify which environmental factors
influence this trade-off. We conducted a literature review and also distributed questionnaires to
researchers in 2001-2003, from which we received 83 completed surveys from 10 countries. We
found that throughout most of their range, male eiders came onto colonies to attend females, although
there was regional variation. Specifically, males were most likely to attend females on larger singleisland
colonies and colonies within archipelagos that were both free of continuous adult predation
risk and that had stunted or no vegetation. Thus, males rarely ventured onto colonies when predators
had regular access to them and/or where tall vegetation conferred an advantage to the predator. We
conclude that male common eiders are behaviorally constrained in some areas of their range under
situations where the costs incurred by venturing onto colonies (predation risk) appear to outweigh the
potential benefits gained by attending females (increased annual reproduction), and also that males
have the behavioral capacity to respond to shifts in this trade-off. This latter conclusion is supported
by the finding that at two locations where mammalian predators were recently removed, males visited
colonies to attend females where they had not previously.
NOV. 7-11, 2005 ANNAPOLIS, MARYLAND, USA
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