WatchList Species Account for Black-vented Shearwater (Puffinus opisthomelas)

Qualifies for the list as a Red List Species

Photo: Glen Tepke

Unlike many other shearwaters, the Black-vented Shearwater is a coastal species, most often seen within 25 km of land. It breeds only on remote desert islands off the Pacific Coast of Baja California, within productive up-welling zones of the California Current. The islands are characterized by having little vegetation and no native mammalian predators. A large percentage of the population nests on a single island, Natividad, Baja California Sur, where numbers are estimated at some 75,000 pairs. On Natividad, however, there has been considerable mortality from feral cats. One model estimates that the population growth there will decrease by 4% annually with the presence of cats but that the population would be stable if the cats were removed.

Like many other tube-nose seabirds, it nests in burrows or rocky crevices and is nocturnal, making it a difficult species to study. During nonbreeding it ranges as far north as Monterey Bay, California, and south along the coast to central Mexico, as well as in the Gulf of California. The overall breeding population is thought to be decreasing.

Among the threats to the species is degradation of habitat; Natividad Island is inhabited and a town has been built on what was once some of the densest nesting habitat on the island. In addition, there is a road through the colony and a trash dump as well. Island residents sometimes drive through the colony at night, disorienting the birds. Rats are unknown on any of the nesting islands and preventing their introduction is a priority. There is a program on Natividad to trap and remove cats and there are also programs to educate the local population as to the conservation value of the island and the importance of protecting the shearwaters. Goats and sheep were removed from Natividad but the effect on shearwaters is unknown.