Characterization of Seabirds, California North Coast MPA Baseline Study, 2014 to 2015

We completed four distinct projects to collect baseline data at varying spatial and temporal scales. First, we used data from aerial photographic surveys conducted from 1989-2014 to investigate region-wide trends in the populations of Common Murres and Brandt’s Cormorants. We used 173 observations of Common Murre colony abundance at 14 colonies and 123 observations of Brandt’s Cormorant nest abundance at 10 colonies over the 26-year study period. Additionally, aerial photographic surveys conducted in 2014 were used to document location and abundance of Common Murre, Brandt’s Cormorant, and Double-crested Cormorant across the NCSR.

Second, at a more localized scale, we monitored Common Murre reproduction, foraging effort, and diet in 2014 at Castle Rock National Wildlife Refuge using a robotic, remotely-controlled video recording system. Although this is only one of the seabird colonies in the NCSR, it the largest and served to inform our understanding of the mechanisms of population change across the region. Common Murre are very visible and thus ideal for monitoring fine scale patterns in reproduction and changing diet. We measured date of nest initiation, hatching success, fledging success, overall reproductive success, time allocation, provisioning rate, and diet composition via the video. Information gained from these surveys were combined with comparable data from 2007-2013 at Castle Rock to assess baseline condition and variability of these metrics over an 8-year period.

Third, in 2014-2015 we conducted ground-based surveys of coastally breeding seabirds inside and outside of six MPAs to establish a framework for continued MPA monitoring. For this, we conducted intensive monitoring of six species likely to benefit from MPA establishment: Pigeon Guillemot, Brandt’s Cormorant, Pelagic Cormorant, Double-crested Cormorant, Western Gull, and Black Oystercatcher. We collected data on breeding population size, breeding productivity, foraging rates and rates of human-caused disturbance inside and outside of each MPA. We monitored productivity by following individual nests visible from land and calculated annual breeding productivity as number of fledglings produced per breeding pair. We monitored foraging from land-based observation points, recording all birds foraging within a 1 km radius of an observation point. We calculated foraging rates as number of birds foraging per hour of observation. We recorded all human-caused disturbances observed during any land-based survey and calculated disturbance rates as number of disturbances per hour of observation.