Historical Diversity of Cormorants and Shags from Amchitka Island, Alaska

Abstract

We studied the historical biodiversity of cormorants and shags in the central Aleutians by examining the presence and abundance of bones deposited in two large Aleut middens located on Amchitka Island, Alaska. The temporal range of discrete strata in these deposits was from Russian-era contact to about 2,650 years before present. We found six species in these middens: Pelagic, Red-faced, and Kenyon's Shags (Stictocarbo [Phalacrocorax] pelagicus, S. urile, S. kenyoni), Double-crested (Hypoleucus [Phalacrocorax] auritus), Japanese (Phalacrocorax capillatus) and Pallas's Cormorants (Compsohalieus [Phalacrocorax] perspicillatus), ranked in order of abundance. Historical patterns of abundance differed among species. Japanese and Pallas's Cormorants were most likely chance arrivals to the island; Double-crested Cormorants were not found post-contact and we hypothesize that Arctic Foxes may have extirpated them here; Pelagic and Red-faced Shags have remained in constant proportion over the years and abundances may relate to environmental or climatic change. Little is known about S. kenyoni. These results suggest that the diversity of the marine coastal avifauna has experienced dynamic change during the late Holocene and that the distributions of shags and cormorants in particular were different than now known.