Apparent adult annual survival and population trends of Black Oystercatcher (Haematopus bachmani) breeding in British Columbia, Canada

Black Oystercatcher (Haematopus bachmani) is an important indicator species for the ecological integrity of rocky coastal ecosystems of western North America. From 2007 to 2022, 49 Black Oystercatchers were banded and resighted in subsequent years in and around Pacific Rim National Park Reserve on Vancouver Island, British Columbia, Canada. We used Cormack-Jolly-Seber mark-recapture models on 16 years of encounter histories to estimate apparent adult annual survival (u), encounter probability (p), and to determine if there was a sex effect on apparent survival. The apparent survival estimate was high (0.91 +/- 0.02), as reported for other oystercatcher species. Apparent survival was not sex-dependent, but encounter probability was 9.8% higher in females (0.96 +/- 0.02) than in males (0.87 +/- 0.03), for reasons we cannot definitively establish. The population trend in the studied population for 2008-2022 was estimated at 3.47 +/- 0.50%, indicating a growing population with an apparent surplus of adult individuals. These survival, encounter, and population trend estimates are important for future monitoring of the Pacific Rim and other Black Oystercatcher populations.