Restoration and Monitoring of Common Murre Colonies in Central California: Annual Report 2012
Efforts in 2012 represented the 17th year of restoration and associated monitoring of central California seabird colonies by the Common Murre Restoration Project (CMRP). This project was initiated in 1996 in an effort to restore breeding colonies of seabirds, especially Common Murres (Uria aalge), harmed by the 1986 Apex Houston, 1998 Command and extended Luckenbach oil spills, as well as gill net fishing, human disturbance, and other factors. From 1995 to 2005, the primary goals were to restore the previously extirpated Devil’s Slide Rock colony using social attraction techniques, and to assess restoration needs at additional central California colonies. Since 2005, efforts have been focused mainly on surveillance and assessment of human disturbance at central California Common Murre colonies. Additionally, the outcome of initial restoration efforts at Devil’s Slide Rock continues to be monitored. These data inform outreach, education and regulatory efforts by the Seabird Protection Network (coordinated by the Gulf of the Farallones National Marine Sanctuary) and allows for assessment of the success of those efforts. The goal of the Seabird Protection Network is to restore central California breeding colonies, primarily through reduction of human disturbance, to compensate for losses during the Luckenbach and Command oil spills. Surveillance and monitoring were conducted almost daily from mid-April to mid-August at the following Common Murre colonies in central California: Point Reyes, Devil’s Slide Rock & Mainland, and the Castle-Hurricane Colony Complex. Another four colonies were surveyed weekly or bi-weekly including three in the Drakes Bay area (Point Resistance, Millers Point Rocks, and Double Point Rocks). Human disturbance rates associated with planes, helicopters, and watercraft were calculated. Seasonal attendance patterns, productivity, adult co-attendance patterns (the percentage of observation time that both parents are present at a nest site) and reproductive performance of Common Murres were also assessed. Additionally, population sizes and/or productivity of five other seabird species were assessed. Bird and nest counts were conducted three times per week at Bird Island and once per week at San Pedro Rock. Detections of aircraft and watercraft (boats) and associated disturbances are reported as a rate per observation hour and compared to a baseline (average of 2005-2006 rates). At Point Reyes, the combined aircraft and boat detection rate was less than the baseline mean (including aircraft, boats, and other), but greater than in 2011. The combined disturbance rate was less than any year since 2002. Detection and disturbance rates at Drakes Bay colonies were also less than the baseline mean, with no observed disturbance events. Devil’s Slide Rock & Mainland (DSRM) continued to have the greatest combined aircraft and boat detection and disturbance rates of all colonies. At DSRM, overall detection and disturbance rates were the greatest recorded to date, largely due to fixed-wing aircraft rates. Most disturbances were agitation events (i.e., no flushing or displacement) but several flushing events occurred, mostly from low helicopter overflights. At the Castle-Hurricane Colony Complex, the combined aircraft and boat detection rate was the least since 2007, but the disturbance rate was slightly greater than the baseline mean (but less than in 2011). xiv Unmarked planes and helicopters (e.g., private or charter), followed by military aircraft, were the most commonly observed aircraft and caused the majority of disturbances at all monitored colonies. The majority of watercraft observed were small private recreational boats (68%) followed by sailboats (11%). One small fishing boat at DSRM was responsible for the only boat-related disturbance. Four vessels were recorded inside state Special Closures at Devil’s Slide Rock and Double Point Rocks/Stormy Stack, but only one resulted in disturbance to seabirds. The peak count of 1,499 Common Murres on Devil’s Slide Rock was 70% greater than the 2011 peak count, and greater than the previous record count of 1,003 murres recorded in 2009. Murre productivity, or reproductive success, was greater than average at Devil’s Slide Rock and Castle Rocks & Mainland despite some Brown Pelican disturbance. Major and prolonged disturbances from Brown Pelicans (Pelecanus occidentalis) at Point Reyes Headlands, Point Resistance, and Double Point Rocks resulted in near total murre reproductive failure. Infrequent co-attendance of murre breeding pairs during the chick-rearing period at Devil’s Slide Rock indicated that murres spent a substantial amount of time foraging to provision young. There were fewer Brandt’s Cormorant (Phalacrocorax penicillatus) nests counted in 2012 than in 2011 at all colony complexes but CHCC. Productivity in 2012 was also less than in both 2011 and the long-term means at all monitored colonies. Numbers of Pelagic Cormorant (Phalacrocorax pelagicus) appeared to be relatively great but productivity at Devil’s Slide Rock and Mainland was the less than any other year on record. Productivity of Western Gulls (Larus occidentalis) was monitored only at DSRM and CHCC. Numbers of breeding Western Gulls were more variable among colonies than in 2011, and productivity of monitored nests was relatively low.