Federico Craveri and changes in nesting seabirds on Isla Rasa, Gulf of California, since 1856

Abstract

Isla Rasa in the Gulf of California has been recognized as an important seabird breeding island for more than 150 y. Yet during most of this period, the island suffered human disturbances that severely reduced seabird nesting success. Today, nearly two decades after disturbances ended, Isla Rasa supports about 90% of the global populations of Heermann's gulls (Larus heermanni) and elegant terns (Thalasseus elegans), plus smaller populations of other species. However, the recently available 1856 journals of Italian naturalist Federico Craveri, and the oral traditions of the Comcaac (Seri people), suggest that the array of nesting species has changed. Apparently, California brown pelicans (Pelecanus occidentalis californicus) abandoned Isla Rasa as a breeding site at the onset of disturbances, and terns first colonized it around 1920.