Black-legged kittiwakes ( Rissa tridactyla ) readily consume Arctic cod ( Boreogadus saida ) in the Canadian Arctic: insights from stomach content and stable isotope analyses

The Arctic is undergoing rapid declines in sea ice and changes in Arctic ecosystems. The diet of one of the Arctic’s most abundant seabirds, the black-legged kittiwake ( Rissa tridactyla), has been used as an indicator of ecosystem changes in the European Arctic, yet little is known about their diet in the Canadian Arctic. We quantified the stomach contents of kittiwakes near Qikiqtarjuaq and Mittimatalik (Pond Inlet), Nunavut, in the Canadian Arctic, and assessed if stable carbon (δ 13 C) and nitrogen (δ 15 N) isotopes in livers differed from that of the dominant prey in their stomachs. Based on stomach contents, prey did not significantly differ between regions, where the dominant prey was Arctic cod ( Boreogadus saida). However, after accounting for dietary discrimination, δ 13 C and δ 15 N values of kittiwake liver were at a lower trophic level than that of Arctic cod muscle. Thus, while kittiwakes do readily consume Arctic cod, stomach content analysis may underestimate soft tissue prey in their diet, such as invertebrates. Future research should include regurgitate and faecal samples to better understand kittiwake diet in the Canadian Arctic. Nevertheless, as climate change impacts continue to increase, this study provides important benchmark information for monitoring changes in these Arctic-breeding seabirds.