Decline in breeding of the Great Black-backed Gull, Larus marinus, and the Herring Gull, L. argentatus, on Boot Island, Nova Scotia, 1986 to 2010

Abstract

For over 50 years, Boot Island, Nova Scotia, has supported a significant mixed bird colony: Great Black-backed Gull (Larus marinus), Herring Gull (L. argentatus), Great Blue Heron (Ardea herodias), and Double-crested Cormorant (Phalacrocorax auritus). In 2002, the largest Great Black-backed Gull colony in Canada was located there. Over the last quarter century, the Herring Gull colony has shown a dramatic and near-linear decrease from 727 nests in 1986 to 67 in 2000; in 2010, only two nests remained. The number of Great Black-backed Gull nests has also declined by 44%, from 1467 nests in 1992 to 819 in 2010. These reductions may be partly attributed to factors external to the colony, such as changes in regional fisheries and better landfill management. However, a more immediate problem may be nest predation and disturbance by American Mink (Neovison vison), Raccoon (Procyon lotor), Coyote (Canis latrans), and Bald Eagle (Haliaeetus leucocephalus).