Black-vented shearwater (Puffinus opisthomelas)
|Size||Length: 35 - 38 cm (2)|
Wingspan: 76 - 89 cm (2)
The black-vented shearwater is classified as Near Threatened (NT) on the IUCN Red List (1).
Unlike most other species of shearwater, the black-vented shearwater (Puffinus opisthomelas) forages for food relatively close to the shoreline and can commonly be seen from the Californian coast (3) (4).
The black-vented shearwater is named after the distinct dark underside of its tail (2). The upperparts of the black-vented shearwater are blackish-brown and the underparts are a dirty white colour. The black-vented shearwater has legs that are set far back on its body that provide very little support, and while this is excellent for swimming, it makes it a clumsy and awkward walker on land (2).
The black-vented shearwater is found off the Pacific coast of North America. This species breeds on six islands off the western coast of Mexico, including Guadalupe, San Benito and Natividad, and will disperse as far North as British Columbia (2) (3) (5).
The black-vented shearwater nests in burrows dug in sandy soil or in rocky crevices (2) (6). This species forages over warm coastal waters within about 10 miles of the shore (4).
The black-vented shearwater has a fluttering flight pattern, effortlessly gliding close to the waters surface (6). This species displays impressive agility while hunting, either snatching prey from the surface or diving up to 20 meters into the ocean to catch fish, squid and sometimes crustaceans (2).
The black-vented shearwater forms colonies for at least ten months of the year, arriving at the colony site during the night in order to reduce predation by western gulls (Larus occidentalis). The nesting colonies can appear to be deserted by day, but at night they come alive with the calling of shearwaters. Many individuals remain in the nesting area year-round, but some disperse along the coast to the north and south after breeding (2).
Nest burrows are about 95 centimetres long, with the narrow entrance allowing just one individual to pass at a time (2). To create the nest burrow in sandy soil, the black-vented shearwater uses its bill to break apart the sand, and will scrape out the burrow with its webbed feet (2). The nests are reused each breeding season (6). The eggs are laid in March and April, and hatching begins in early May (5). The young fledge the nest in July and August. It is thought that the black-vented shearwater reaches maturity after five to six years (4).
This species has declined in number in the past, but many of the threats to the black-vented shearwater have now been removed, which will hopefully lead to an increase in the population size (1).
The black-vented shearwater has previously been threatened by introduced species to its breeding islands and future introductions of non-native species could rapidly reduce population numbers if not prevented (6). Introduced feral cats and dogs predate upon nesting black-vented shearwaters, causing high mortality rates. Introduced herbivores such as sheep, goats and rabbits cause soil erosion and nest burrows to collapse, reducing breeding habitat for the black-vented shearwater (5).
The construction of roads and the establishment of a small fishing community have also reduced the available black-vented shearwaters habitat on some of the islands (5).
The largest colony of black-vented shearwaters is found on Natividad Island, which is part of the Vizcaino Biosphere Reserve. This gives the island legal protection, although little active management occurs (5) (7). With the cooperation of the local fishing community, goats and sheep were eradicated from the island in 1998. Cats on the island were controlled from 1998 and finally removed by 2002 (5).
Conservation measures have already had a huge positive impact on the black-vented shearwater. Preventing the reintroduction of predators to the islands, banning further construction and closing some of the islands to visitors may all benefit the black-vented shearwater (5) (6).
Find out more about the black-vented shearwater and its conservation:
Birdlife International – Black-vented shearwater:
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- Crustaceans: diverse group of animals with jointed limbs and a hard external skeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.
- Herbivore: an animal that consumes only vegetable matter.
- Nocturnal: active at night.
IUCN Red List (June, 2009)
Keitt, B.S., Tershy, B.R. and Croll, D.A. (2000) Black-vented shearwater,Puffinus Opisthomelas. In: Poole, A. (Ed) The birds of North America. Cornell Lab of Ornithology, Ithaca. Available at:
- Croll, S,D., Keitt, B.S. and Tershy, B.R. (2000) Dive depth and diet of the black vented shearwater, (Puffinus opisthomelas). The Auk, 117(2): 507-510.
- Wells, J.V. (2003) Birder's Conservation Handbook: 100 North American Birds at Risk. Princeton University Press, New Jersey.
Birdlife International (November, 2011)
- Keitt, B.S., Tershy, B.R. and Croll, S,D. (2003) Breeding biology and conservation of the Black-vented Shearwater Puffinus opisthomelas. IBIS, 145(4): 673-680.
- Lebbin, D.J., Parr, M.J. and Fenwick, G.H. (2010) American Bird Conservancy Guide to Bird Conservation. The University of Chicago Press, Chicago.