Breeding Biology of the Common Murre at Triangle Island, British Columbia, Canada, 2002–2007

Abstract

Abstract Triangle Island, the most westerly of the Scott Islands, supports the larger of 2 active Common Murre (Uria aalge) breeding colonies (about 3000 pairs) in British Columbia, Canada. However, little is known about the species' breeding ecology at this site. Here, we report on investigations of murre biology at Triangle Island between 2002 and 2007. Possibly indicative of their zoogeographic affinities, Triangle Island Common Murres are more similar in size to those that breed at colonies to the north than to the south. Murres were first seen on the colony between late March and early April. The 1st eggs were laid in mid- to late May, and latest eggs (1st or replacement) in mid-July. Median laying dates varied by about 25 d across 5 y (2003 to 2007). Despite differences in adult size, eggs laid at Triangle Island were similar in size to those at murre colonies across western North America. Breeding success for murres at Triangle Island ranged from 54% (2007) to 82% (2004) over 5 y, which is on the h...