Diet of Leach's Storm-Petrels (Hydrobates leucorhous) among Three Colonies in Atlantic Canada

Abstract

Hydrobates leucorhous (Leach's Storm-petrel) is widely distributed throughout the Northern Hemisphere, but colonies in Atlantic Canada are declining. We assessed the diet of Leach's Storm-petrels from colonies at Country and Bon Portage islands, NS, Canada, and Kent Island, NB, Canada, during the chick-rearing period in 2018 and 2019. Prey composition varied between years and between colonies. In 2019, when sample sizes were similar across colonies, occurrence of fish varied widely among colonies, being high at Country Island (77.3%), intermediate at Bon Portage Island (22.2%), and low at Kent Island (4.8%). Euphausiids, the main crustacean component of the diet across all colonies, occurred frequently at Kent (100%) and Bon Portage (94.4%) islands, and in 63.6% of samples at Country Island. Pooled samples from all 3 colonies in this study had significantly lower fish occurrence (P < 0.01) but similar occurrence of crustaceans (P = 0.93) than previous studies of the diet of Leach's Storm-petrels elsewhere in eastern North America. The dietary variation we found among Leach's Storm-petrel colonies may explain some of the patterns of mercury in tissues for birds at these sites.