Black-vented Shearwater
Black-vented Shearwater
Puffinus opisthomelas
At a Glance
Most shearwaters range widely over the ocean far from land, and most of those seen off our Pacific Coast nest only in the southern hemisphere. The Black-vented Shearwater is an exception, nesting on islands off northwestern Mexico, traveling only short distances north along the California coast, and usually staying within a few miles of shore. Observers at coastal lookouts may see this bird in late fall, flying with rapid wingbeats and short glides low over the waves.
All bird guide text and rangemaps adapted from Lives of North American Birds by Kenn Kaufman© 1996, used by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Category
Gull-like Birds, Shearwaters and Petrels
IUCN Status
Near Threatened
Habitat
Coasts and Shorelines, Open Ocean
Region
California, Northwest
Behavior
Flap/Glide, Rapid Wingbeats, Swimming
Population
160.000
Range & Identification
Migration & Range Maps
Moves north from Baja into California's coastal waters in fall. Numbers and timing variable: when sea temperature is high, may arrive early and in large numbers. Some also may move well to south of breeding range, but southward migration poorly known.
Description
12 1/2 -15" (32-38 cm). Small, with faster wingbeats than other western shearwaters. Very dingy around head and throat, dark under base of tail. Manx Shearwater, rare off west coast, is similar in size and flight but whiter below, especially under base of tail.
Size
About the size of a Crow, About the size of a Robin
Color
Black, Brown, White
Wing Shape
Broad, Pointed, Short, Tapered
Tail Shape
Pointed, Rounded, Wedge-shaped
Songs and Calls
Usually silent at sea.
Call Pattern
Flat, Undulating
Call Type
Hoot, Odd, Raucous, Scream
Habitat
Open ocean near coast. Found closer to shore than most shearwaters, over continental shelf within a few miles of the coast. Favors warm waters at all seasons: fewer move north along California coast in years when sea surface temperature is lower. Nests on islands with enough soil for burrowing or with natural crevices in rock.
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Behavior
Eggs
One. Dull white. Incubation probably by both sexes, as in other shearwaters; incubation period not well known.
Young
Both parents probably feed young, by regurgitation. Development of young and age at first flight not well known, but young probably remains in nest at least 2 months.
Feeding Behavior
Forages by seizing items at or just below surface while swimming, by plunging into water from low flight, or by making shallow dives from surface. Apparently does not dive as often nor swim as well underwater as the similar Manx Shearwater.
Diet
Probably mostly fish. Diet not well known. Off southern California may eat mostly small fish, including herring and sardines. May also eat small squid, crustaceans.
Nesting
Breeding behavior not well known. Nests in colonies on islands. Active around colonies only at night. Both members of pair may rest in nest burrow during daytime before egg-laying. Nest: Site is in burrow in ground, sometimes in crevice in rock. Burrow may be more than 10' long, often with turns to the side rather than straight; probably both sexes help dig burrow, as in related species. Nest chamber at end of burrow may have a few bits of plant material or may be unlined.
Conservation
Conservation Status
Numbers appear to be stable, but vulnerable to introduced cats and other predators on nesting islands.
Climate Threats Facing the Black-vented Shearwater
Choose a temperature scenario below to see which threats will affect this species as warming increases. The same climate change-driven threats that put birds at risk will affect other wildlife and people, too.