Roosting Brown Pelicans at San Nicolas Island, California, 1972–2006

Abstract

Abstract. To assist long-term protection of roost sites, roosting patterns of California Brown Pelicans (Pelecanus occidentalis californicus) at San Nicolas Island (SNI), California, were assessed for the 1972–2006 period. SNI was used for roosting year-round, with most birds likely from nearest primary breeding colonies (Santa Barbara and Anacapa islands) within the Southern California Bight subpopulation. Among non-El Nino years, monthly diurnal counts varied, but ranged from less than 100 birds during the breeding season to approximately 1,000 during fall. Influxes from the large Gulf of California subpopulation also occurred on occasion, best demonstrated by prolonged increased numbers during strong El Nino conditions in 1972–1973, possibly reflecting delayed or skipped breeding and increased prey availability near the outer California Channel Islands. The peak estimate of 13,500 night-roosting pelicans was on 16 November 1972 during these El Nino conditions. Most pelicans roosted diurnally on the nor...