Technical Report

Restoration and Monitoring of Common Murre Colonies in Central California: Annual Report 2013

Efforts in 2013 represented the 18th 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 directed towards surveillance and assessment of human disturbance at central California Common Murre colonies. Additionally, the outcome of initial recolonization efforts at Devil’s Slide Rock continues to be monitored. This data informs 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 seabird breeding colonies primarily through reduction of human disturbance. In this report, we summarize seabird monitoring results from the 2014 breeding season including human disturbance, productivity, relative population sizes, and other data. At Point Reyes Headlands (PRH), the combined aircraft and watercraft detection rate was less than the baseline mean (average of 2005-2006, including aircraft, watercraft, and other), and less than in 2012. The combined disturbance rate at PRH was less than the baseline mean, but greater than in 2012 – driven by five agitation events caused by helicopters. Detection and disturbance rates at Drakes Bay Colony Complex (DBCC) were also less than the baseline mean, with no observed disturbance events. Devil’s Slide Rock and Mainland (DSRM) continued to have the greatest combined aircraft and watercraft detection and disturbance rates of all colonies. However, detection and disturbance rates in 2013 were both less than the baseline mean, and less than in 2012. Agitation events accounted for most disturbances, with only four flushing events observed in 2013. At the Castle Hurricane Colony Complex (CHCC), the combined aircraft and watercraft detection rate was less than the baseline mean and 2012 rates, and none resulted in disturbance. General aviation planes and helicopters (e.g., private or charter), followed by military helicopters, and the CDFW survey aircraft were the most commonly observed aircraft and caused the majority of disturbances at all monitored colonies. The majority of watercraft observed were private recreational fishing boats, but none caused any disturbance in 2013. Two vessels were recorded inside state Special Closures at Devil’s Slide Rock, including a private fishing boat and a kayak. Neither vessel caused any disturbance. The aerial photograph count of 2,001 Common Murres on Devil’s Slide Rock (DSR) was 55% greater than the 2012 count. This was also the greatest count since murres recolonized the rock in 1996, and similar to counts obtained in 1979-1982, prior to previous colony extirpation. The peak land-based count on DSR was 1,527 murres, 1.9% greater than the 2012 peak count of 1,499. Murre productivity, or reproductive success, was greater than average at DSR and Castle Rocks and Mainland (CRM), and near average at PRH. Above average co-attendance of murre xiv breeding pairs during the chick-rearing period at DSR suggested that prey was abundant near the colony at that time. There were more Brandt’s Cormorant (Phalacrocorax penicillatus) nests counted in 2013 than in 2012 at PRH, MPR, DPR and CRM; and fewer nests at PRS and DSRM. However, these counts were incomplete; aerial photograph counts are needed for a better assessment. Brandt’s Cormorant productivity in 2013 was greater than long-term means and greater than in 2012 at all monitored colonies. Productivity of Pelagic Cormorants (Phalacrocorax pelagicus) was monitored only at DSRM and productivity of Western Gulls (Larus occidentalis) and Black Oystercatchers (Haematopus bachmani) was monitored only at DSRM and CHCC. Productivity of Pelagic Cormorants at DSRM was 49% greater than the long-term average, and the greatest recorded to date. Western Gull productivity was 56% greater at DSRM and 51% less at CHCC than long-term averages.