A new study, gracing the cover of The Proceedings of the Royal Society B explains why eider ducks wintering in the sea ice of the Canadian Arctic have been observed resting and not feeding during slack tidal currents; a period traditionally thought to be the most optimal foraging time for sea ducks.

This seemingly counterintuitive process reflects constraints of eiders imposed by the slow digestion of their hard-shelled benthic prey and the predictable cycle of variable tidal currents which, at its extremes, forces eiders out of the water entirely to sit on the sea ice. 

This research, led by Environment Canada, is helping to assess the vulnerability of eiders to starvation and population decline under changing environmental conditions that are now ongoing in Hudson Bay.

This population of eiders faces extremely low temperatures, heavy sea ice conditions, and high risks of mass starvation. Eiders manage to feed twice during a single tide cycle and digest during slack currents, and in doing so, they maximize their long-term energy gain over entire tide cycles during the polar winters, say the researchers.

As an educational complement to the ongoing research, Joel Heath and the community of Sanikiluaq have recently finished a documentary film entitled, People of a Feather, which was financially and logistically supported by the International Polar Year and Environment Canada. The film dramatically depicts the region’s natural history and Inuit life in a changing environment.

Source: Heath, J.P., H.G. Gilchrist and R.C. Ydenberg. 2010. Interactions between rate processes with difference timescales explain counterintuitive foraging patterns of arctic wintering eiders. 277(1697): 3179-3186.

Related paper: Heath, J. and H.G. Gilchrist. 2010. When foraging becomes unprofitable: energetics of diving in tidal currents by arctic wintering common eiders. Marine Ecology Progress Series 403: 279-290.

Contact: Grant Gilchrist, (613) 998-7364, Wildlife and Landscape Science Directorate