Terminal Pleistocene–Holocene Avifauna of San Miguel and Santa Rosa Islands: Identifications of Previously Unidentified Avian Remains Recovered from Fossil Sites and Prehistoric Cave Deposits

We provide an update to the fossil avifauna of San Miguel and Santa Rosa Islands based on the identification of 3509 small bird bones recovered from fossil sites on Santa Rosa and from 3 archaeological-paleontological cave deposits and 20 fossil sites on San Miguel. This work adds 64 species to the fossil avian community of these 2 islands, increasing the previous total from 83 to 147 species, making this the richest Late Pleistocene-Holocene coastal avifaunal assemblage recorded for California. Of the 64 newly identified species, 62 are new additions to the Channel Islands fossil avifauna and 40 are new to the fossil avifauna of California. Twenty-two species were confirmed to have nested on San Miguel Island during the Holocene based on the identification of juvenile/immature bones. At least 4 land birds (Burrowing Owl [Athene cunicularia], Island Scrub-Jay [Aphelocoma insularis], Bewick's Wren [Thryomanes bewickii], and Spotted Towhee [Pipilo maculatus]) that nested prehistorically on San Miguel have disappeared from the modern record there. Island Scrub-Jay bones were identified from 3 fossil sites on San Miguel and 1 site on Santa Rosa, providing the first confirmation that this species lived on both islands during the Pleistocene and Holocene. Island Scrub-Jays disappeared from San Miguel Island sometime in the Late Holocene, but a small population may have lingered on Santa Rosa island into historic times before dying out. Destruction of island scrub and woodland habitats following the introduction of livestock in the mid-19th century probably caused the extirpation of resident breeding populations of Bewick's Wren and Spotted Towhee from San Miguel Island and Island Scrub-Jay from Santa Rosa Island.