DRAFT EVALUATION OF POTENTIAL BENEFITS TO SEABIRDS FROM PROPOSED MARINE PROTECTED AREAS IN THE MLPA NORTH CENTRAL COAST STUDY REGION, CALIFORNIA

Gerard J. McChesney MLPA Master Plan Science Advisory Team January 2008 In this document, draft proposed marine protected areas (MPAs) for the MLPA North Central Coast Study Region (NCCSR) are evaluated for their potential benefits to seabirds in relation to Goal 2 of the California Marine Life Protection Act. Evaluations follow the methods described in “Methods Used to Evaluate Draft MPA Proposals in the North Central Coast Study Region (Draft)” from January 7, 2008. One change from that document is that no rankings of level of benefit (e.g., high, medium, low, none) have been given because the variability in population sizes between species made categorizations too subjective and potentially misleading. Information includes all species (where appropriate) and species most likely to benefit. Evaluations are subdivided by subregions (or, bioregions; North; South; and Farallon Islands) because of the large differences in species composition and abundances between these areas. As upper trophic level predators, seabirds are important components of marine ecosystems. Seabird diets vary, but generally include various juvenile fish and invertebrates that are locally abundant. In central California, important seabird prey include rockfish, anchovies, various flatfish, cottids, tomcod, krill, mysid shrimp and squid, among others (e.g., Ainley et al. 1990). Seabirds have been recognized as an efficient monitoring tool for ocean conditions and, in some cases, for predicting stocks of important fisheries (e.g., Ainley and Boekelheide 1990, Cairns 1992, Sydeman et al. 2001, Mills et al. 2007, Roth et al. 2007). Ecologies of the different species of seabirds vary. For example, many species such as albatrosses, shearwaters, and petrels only come to land to breed and spend the remainder of their lives at sea. Many other species, such as most pelicans, cormorants, and gulls, come to shore on a daily basis to rest, preen, or bath. For pelicans and cormorants, trips ashore are essential for survival because their wettable plumage must be dried to avoid hypothermia. For most species, breeding habitats are on offshore rocks, islands, or mainland cliffs free of mammalian predators. Seabirds may benefit in several ways from marine protected areas in the NCCSR. For example, most species are known to be sensitive to human disturbance to varying degrees (summarized in Carney and Sydeman 1999). Impacts of human disturbance are known to be greatest at breeding sites, where reproduction can be dramatically affected. Because most seabirds are colonial breeders (e.g., nesting in high concentrations), high proportions of populations can be affected by severe or frequent disturbances. Similarly, seabirds and other waterbirds often concentrate at resting sites (“roosts”) and foraging areas where they can be sensitive to disturbance (e.g., Jaques et al. 1996, Kuletz 1996, Rodgers and Schwikert 2002, Jaques and Strong 2002, Speckman 2004, Peters and Otis 2006). Because of these sensitivities, many observers have recommended disturbance-free “buffer zones” or other management actions around colonies, roosts, or