WatchList Species Account
for Black-vented Shearwater (Puffinus opisthomelas) |
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 15
miles 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. These 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, the Black-vented Shearwater
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