The park islands support important nesting areas for fourteen species of seabirds with a number of species reaching their northern or southern breeding distributional limits at the islands. Prince Island (included within the San Miguel Island column) and Santa Barbara Island support the largest number of breeding seabirds of any of the Channel Islands. Large breeding populations of Western Gulls, Cassin’s Auklets, and Brandt’s Cormorants occur on the Park islands. Most of the world’s population of Scripps’s Murrelets, more than 50% of the world’s population of Ashy-Storm-Petrel, and the only nesting populations of Brown Pelicans along the west coast of the United States can be found at the Channel Islands.
Of the 387 species of birds observed to date on the Channel Islands, 82 are thought, to have nested on one or more of the park islands. Eleven of the 60 species of land birds that have nested on the park islands are represented by endemic species or subspecies – forms that are found on the islands and nowhere else. The island Scrub Jay is found only on Santa Cruz Island. Other endemics like the non-migratory Allen’s Hummingbird, Channel Island Flycatcher, Island Loggerhead Shrike, Island Horned Lark, Santa Cruz Island Bewick’s Wren, Dusky Orange-crowned Warbler, San Clemente Spotted Towhee, Santa Cruz Island Rufus-crowned Sparrow, and Channel Island Song Sparrow are found on two or more of the islands.