PARENT SESSION
Poster Session 39: Late Breaking and Newsworthy Posters
Friday, August 12, 8:30 AM - 10:30 AM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Complex behavioural patterns of Common Eiders wintering in the Canadian Arctic: the role of abiotic and physiological rythms.

Heath, Joel^*,1, Gilchrist, H. Grant², Ydenberg, Ronald¹, ¹ Simon Fraser University, Burnaby, British Columbia, Canada² Canadian Wildlife Service, Ottawa, Ontario, Canada

ABSTRACT- Dynamic oceanographic processes produce variation across a range of spatiotemporal scales. This variation can influence foraging tactics of predators. Morphological and physiological constraints, including cardiovascular (e.g. for endurance and diving) and digestive rates, occur at different frequencies and can also influence responses to environmental variation. Interactions between these biotic and abiotic factors could therefore lead to complex scale-dependent behavioural patterns. Yet it is often assumed that short term behavioural observations and foraging currencies can be directly scaled up to longer periods and fitness. We investigated foraging patterns of Common Eiders wintering in sea ice habitats in the eastern Canadian Arctic. This environment presents unique challenges for Eiders attempting to balance their energy budgets, particularly during heavy sea ice conditions in recent winters. While tidal currents are necessary to maintain persistent open water habitats (polynyas), we show that strong currents also increase the time and energy costs of diving to forage on benthic invertebrates. Underwater video indicates travel time increases whereas time at depth (foraging) decreases with increasing current velocity. At high current velocities diving is no longer energetically profitable. These results agree with predictions of static dive cycle models, but do not explain surface pause durations and longer term behavioural patterns. When the time scale of digestion and the tide cycle are considered in a dynamic framework, complex and seemingly counter-intuitive behavioural patterns of Eiders can be understood as adaptive. Specifically, although in the short term it is energetically most profitable to forage during slack currents, net energy gain over the tide cycle is maximized by resting and digesting for extended periods during slack currents. These results are important for elucidating factors important to the foraging ecology of aquatic predators, and exemplify the necessity of a multi-scale approach for investigating temporal activity patterns.

Key words: Scaling, Temporal Patterns, Behavioural Ecology, Diving Birds