Effects of climate change, altered sea-ice distribution and seasonal phenology on marine birds

Abstract

The Hudson Bay region supports internationally significant populations of marine birds (>2,000,000 individuals), particularly thick-billed murres (Uria lomvia) and common eiders (Somateria mollissima). The breeding ecology of both of these species is inextricably linked to distribution of sea ice and the timing of its breakup and freeze-up, which determine the availability and distribution of open water in which to feed. For the piscivorous murres, earlier ice breakup is creating a mismatch between the timing of breeding and the peak in food availability, and the birds have not, to date, advanced their breeding phenology to keep up with the pace of environmental change. However, at the end of the season, delayed freeze-up is extending the period that birds can remain in the Bay. Earlier ice breakup may allow migratory eiders earlier access to the benthic mollusks they require to gather nutrient resources prior to breeding, and for the non-migratory eider population in southern Hudson Bay, warmer temperatures mean more open water (i.e., larger and more numerous polynyas and floe edges) needed to gather food supplies necessary for their overwinter survival. Thus, the effects of changes in sea ice cover vary according to each species' ecological needs. We anticipate considerable changes in populations of marine birds in the Hudson Bay region in future, due to direct and indirect effects of reduced sea ice cover. © 2010 Springer Netherlands.