Alca marina di Scripps

Tassonomia

Nome scientifico

Synthliboramphus scrippsi

Autorità

(Green & Arnold, 1939)

Ordine

Caradriformi

Famiglia

Alcidi

Genere

Synthliboramphus

Areale e habitat

Areale riproduttivo

NA, MA : ec North Pacific coast: Channel Is. (s California) and islands off nw, nc Baja California to San Benito (nw Mexico)

Areale non riproduttivo

n to coastal Washington (ec North Pacific Ocean)

Migrazione

Resident species

Comportamento

Scripps's murrelet feeds at sea (but on average not as far from land as Guadalupe murrelet), often in association with large pelagic predatory fish like tuna, on larval fish like anchovies, sardines and Sebastes rockfish. Like all auks it is a wing-propelled diver, chasing down prey under the water with powerful wingbeats. There is some speculation that it may feed cooperatively in pairs, as it is almost always observed in pairs, even during the non-breeding season. It flies well, and can take off without taxiing.<p>It nests in loose scattered colonies on arid islands, typically in small crevices and caves and under dense bushes. It returns to the colony only at night, laying two eggs which are incubated for about a month. As in other synthliboramphine murrelet species (e.g. the ancient murrelet) the chicks are highly precocial, leaving the nest within two days of hatching and running actively towards the sea, where the parents call to them. Once at sea the family swims to offshore waters.<p>Little is known about their time at sea due to difficulties in studying them in this habitat. A female shot at Isla Guadalupe at the end of June was moulting its primary remiges (flight feathers) and unable to fly.

Conservazione

By the end of the 20th century, the Xantus's murrelet complex was considered to be among the most endangered species of auk. This has changed since, but not because the present species' status has improved, but because other auks have become rarer.<p>Scripps's murrelet is mainly threatened by oil spills, as much of its population lives near the busy shipping lanes connecting Los Angeles to other ports. Because a large part of its small population nests in such a small area, a single catastrophic oil spill could have far reaching implications. It is also threatened by introduced species such as rats and feral cats; this threat has been lessened lately by efforts to restore its habitat by removing introduced predators. In 2001 and 2002, Island Conservation, the Channel Islands National Park, California Department of Fish and Game, the U.S. Fish and Wildlife Service, and the National Oceanic and Atmospheric Administration removed invasive rats from Anacapa Island. This effort was paid for by a trust fund from an oil spill settlement.

Tendenza della popolazione

declining