ID Keys: Dark overall with obvious white, wedge-shaped rump
The
Wedge-rumped Storm-Petrel breeds off the west coast of South America, but
they can be found throughout much of the eastern Pacific outside of the
breeding season. In the United States, they are but rare vagrants,
having been found off the California Coast several times. There are
two breeding locations, one in the Galapagos, and one off the coast of Peru.
The two subspecies were formerly known as the Galapagos Storm-petrel and
Peruvian Storm-petrel, respectively, until research revealed they were one
species and they were renamed the Wedge-rumped Storm-petrel. The
Galapagos breeding population is the only storm petrel species that is
active at the breeding colony during daylight hours. It is thought
this unusual behavior may be due to the presence of nocturnal-hunting owls
on the islands.
Habitat
Outside of the breeding season, they are
true pelagics and are typically found quite a distance from the coast.
Diet
Mostly feeds on small fish, crustaceans, and
squid.
Behavior
Forages by flying low over the water,
looking for food. Like other storm-petrels, they will "patter" at the
water's surface as they grab prey items. Most feeding is done at
night.
Nesting
Breeds in colonies. The nest is
placed in a rocky crevice or nook on a cliff. A single egg is laid,
and both parents will help to incubate it. Incubation lasts about 7 weeks.
Migration
Breeds in the Galapagos and other
islands off the coast of western South America. Outside of the
breeding season they can be found well offshore in the eastern Pacific, from
Mexico all the way southward to Chile.
Song
Does make a series of crisp, squeaky
calls, primarily near their breeding sites.
Similar species
Similar in structure to
several other storm petrels, but the large white rump plumage
distinguishes them. The
Wilson's Storm-Petrel is likely the closest in appearance, but the
white on a rump of a Wilson's is less extensive, and a Wilson's has
yellow feet if seen well.
