| Summary: | Castle Rock National Wildlife Refuge is a 6.4 ha island located 0.8 km off the coast of Crescent City, California. Castle Rock is the second largest seabird breeding-colony along the California coast, the largest Common Murre colony in the California Current, and hosts more than 100,000 seabirds. Eleven different species are known to have nested on this island including: Common Murre (Uria aalge), Brandt’s (Phalacrocorax penicillatus), Pelagic (Phalacrocorax pelagicus), and Double-crested Cormorants (Phalacrocorax auritus), Pigeon Guillemots (Cepphus columba), Cassin’s (Ptychoramphus aleuticus) and Rhinoceros Auklets (Cerorhinca monocerata), Tufted Puffins (Fratercula cirrhata), Western Gulls (Larus occidentalis), and Fork-tailed (Oceanodroma furcata) and Leach’s Storm Petrels (Oceanodroma leucorhoa) (Carter et al. 1992). The Aleutian Cackling Goose (Branta hutchinsii leucopareia) population has recovered from less than 800 in 1974 to more than 100,000 today (U.S. Fish and Wildlife Service 2001) and large numbers (~20,000) of geese have been roosting overnight on Castle Rock in the spring. These geese have the potential to alter habitats at the island. Brown Pelicans (Pelecanus occidentalis) have also roosted at Castle Rock in great numbers (1-2,000) during the fall. Castle Rock is situated midway along the U.S. Pacific Coast between two other major seabird colonies in the California Current: the Farallon Islands off the central California coast to the south and Three Arch Rocks off the Oregon coast to the north. Unlike the Farallon Islands, Castle Rock is much closer to shore and thus closer to many types of anthropogenic threats. However it is far enough off shore that observations or protections from the mainland have been very limited. Research and monitoring have been taking place at the Farallon Islands since 1971 (Ainley and Boekelheide 1990) and Three Arch Rocks has been a National Wildlife Refuge since 1907, while Castle Rock does not have a history of monitoring or conservation-based management and was ...
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