Wedge-tailed Shearwater

Identificazione

The wedge-tailed shearwater is the largest of the tropical shearwaters. The two colour morphs of the species are dark and pale; the pale morphs predominate in the North Pacific, the dark morph elsewhere. However, both morphs exist in all populations, and bear no relation to sex or breeding condition. The pale morph has grey-brown plumage on the back, head, and upper wing, and whiter plumage below. The darker morph has the same dark grey-brown plumage over the whole body. The species' common name is derived from the large, wedge-shaped tail, which may help the species glide. The bill is dark and legs are salmon pink, with the legs set far back on the body (in common with the other shearwaters) as an adaptation for swimming.<p>This species is related to the pan-Pacific Buller's shearwater, which differs much in colour pattern, but also has a wedge tail and a thin, black bill. They make up the Thyellodroma group, a superspecies of the large shearwaters that were for a long time included in the genus Puffinus.

Tassonomia

The wedge-tailed shearwater was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the petrels in the genus Procellaria and coined the binomial name Procellaria pacifica. Gmelin based his description on the "Pacific petrel" that had been described in 1785 by the English ornithologist John Latham in his book A General Synopsis of Birds. The type locality was designated as the Kermadec Islands by Gregory Mathews in 1912. The wedge-tailed shearwater is now one of seven species placed in the genus Ardenna that introduced in 1853 by Ludwig Reichenbach. The species is monotypic: no subspecies are recognised. A molecular phylogenetic study published in 2022 found that the wedge-tailed shearwater was sister to Buller's shearwater.

Nome scientifico

Ardenna pacifica

Autorità

(Gmelin, JF, 1789)

Ordine

Procellariformi

Famiglia

Procellaridi

Genere

Ardenna

Areale e habitat

Breeding range: PO, IO : islets of tropical South Indian Ocean: Amirantes and Inner Is. (c, ne Seychelles) and Mascarenes (Malagasy region), Chagos and Cocos (Keeling) (se Indian Ocean), New Guinea region, and w Australia; islets of subtropical and tropical Pacific Ocean: e Australia including Torres Strait is. (ne Australia), Lord Howe and Norfolk is. (far e of Australia), Kermadec Is. (ne of North I., New Zealand); Solomon Is., Vanuatu and New Caledonia; Senkaku (=Pescadores Is.), Ogasawara (=Bonin Is.) and Iwo (= Volcano Is; s of Japan); throughout Micronesia and Polynesia (except Cook and Pitcairn groups); Northwestern and main Hawaiian Is.; and Revillagigedo Is. (far w of c Mexico). Non-breeding range: to Arabian Sea coasts of nw Africa and e Malagasy region, s India and Bay of Bengal in tropical Indian Ocean; through seas of s and e Indonesian Arch.; in Pacific, to Tasmania and waters n of North I. (New Zealand) and to coastal waters of e North Pacific from s Baja California (nw Mexico) to s Panama.

Areale riproduttivo

PO, IO : islets of tropical South Indian Ocean: Amirantes and Inner Is. (c, ne Seychelles) and Mascarenes (Malagasy region), Chagos and Cocos (Keeling) (se Indian Ocean), New Guinea region, and w Australia; islets of subtropical and tropical Pacific Ocean: e Australia including Torres Strait is. (ne Australia), Lord Howe and Norfolk is. (far e of Australia), Kermadec Is. (ne of North I., New Zealand); Solomon Is., Vanuatu and New Caledonia; Senkaku (=Pescadores Is.), Ogasawara (=Bonin Is.) and Iwo (= Volcano Is; s of Japan); throughout Micronesia and Polynesia (except Cook and Pitcairn groups); Northwestern and main Hawaiian Is.; and Revillagigedo Is. (far w of c Mexico)

Areale non riproduttivo

to Arabian Sea coasts of nw Africa and e Malagasy region, s India and Bay of Bengal in tropical Indian Ocean; through seas of s and e Indonesian Arch.; in Pacific, to Tasmania and waters n of North I. (New Zealand) and to coastal waters of e North Pacific from s Baja California (nw Mexico) to s Panama

Migrazione

Migratori completi

Comportamento

Comportamento migratorio: Migratori completi.

Conservazione

Tendenza della popolazione: in diminuzione.

Tendenza della popolazione

in diminuzione