Cassin’s Auklet population trends are assessed through Environment and Climate Change Canada’s (ECCC) Seabird Colony Monitoring Program, which tracks changes in burrow counts at fixed plots and estimates occupancy rate of the colony. Monitoring data are available from five of the 62 breeding colonies on offshore islands in British Columbia, including the large, well-studied colony at Triangle Island, where more than 500,000 nesting pairs breed (Manuwal and Thoresen 1993). Systematic monitoring data prior to 1984 are lacking, but data collected since then suggest that abundance at Triangle Island has fluctuated over time, with an increase observed in the late 1980s/early 1990s, followed by a decrease from the early 1990s through to about 2010, then a fairly strong increase in 2014 (see graph below). Indeed, in recent years, the number of active burrows in ECCC’s long-term monitoring plots at several colonies along the coast has increased, but overall, the population has exhibited little change in abundance in Canada relative to about 1970. However, the reliability of this assessment is considered to be medium because some uncertainty remains; reproductive success appears to differ among colonies (COSEWIC 2014f) and only a fraction of the population is being monitored. The Cassin’s Auklet is currently at an acceptable level relative to its national population goal (see graph below).
Additional information on: Seabird Colony Monitoring Program
