Seabird disturbance monitoring

Seabirds are long-lived, upper trophic level predators that are integral components of marine ecosystems. Marine protected areas (MPAs) can provide both direct and indirect benefits to seabirds. Direct benefits involve reducing the direct interactions seabirds have with humans such as from fisheries and recreational activities. Indirect benefits involve reducing competition with humans for prey resources. As the abundance of prey increases within and adjacent to MPAs, seabirds may benefit as more abundant prey resources lead to increases in their productivity and population sizes. We monitored four coastally breeding seabirds that feed largely on juvenile and other small fishes in nearshore habitats (Brandt’s cormorant, pelagic cormorant, western gull, and California least tern) and one shorebird that feeds on rocky intertidal invertebrates (black oystercatcher). We collected data on baseline population size, productivity, foraging rates, and rates of human-caused disturbance inside and outside of three MPA clusters: Gull Island SMCA, Painted Cave SMCA and Scorpion SMR (Santa Cruz Island); Point Vicente SMR and Abalone Cove SMCA (Palos Verdes); and Cabrillo SMR, South La Jolla SMR/SMCA, and Matlahuayl SMR (San Diego). California least tern diet composition data were collected inside and outside of MPAs including Bolsa Chica Basin SMCA, Bolsa Bay SMCA, Batiquitos Lagoon SMCA, and Tijuana River Mouth SMCA. The long-term objectives of our monitoring are to 1) document how seabirds are using coastal and nearshore habitats in relation to a sample of newly established MPAs within the SCSR and 2) develop seabirds as tools to investigate changes in fish and invertebrate populations inside and outside of SCSR MPAs. Data presented here focus on disturbance monitoring for both roosting and breeding seabirds as well as hauled out marine mammals.