Diet of black guillemots and northern fulmars breeding beside a High Arctic polynya

In the Arctic, the availability of early-season open water (shore leads, polynyas) is a key factor influencing annual reproduction by marine birds, as these relatively productive locations provide the only sites where migrating and breeding birds can feed. We examined the diet of two marine birds, black guillemots (Cepphus grylle) and northern fulmars (Fulmarus glacialis), feeding in the Hell Gate–Cardigan Strait Polynya in the Canadian High Arctic during the breeding seasons of 1980–1984. There was little overlap in prey items consumed between these two species, except that both relied on similar sympagic amphipods. Guillemots fed principally on benthic prey, and compared to earlier High Arctic studies, they consumed proportionally more benthic fish, mysids and decapods. Fulmars appeared to feed on swarms of pelagic or surface prey, and in this polynya they consumed proportionally fewer fish and more polychaetes than has been reported for fulmars at other High Arctic locations. Given that climate change may alter marine food webs by changing the types and availability of prey, our results set a baseline of dietary information for these predators against which future conditions can be compared.