Cassin's Auklet

From Devonshire

Current revision as of 23:09, 7 July 2009

The Cassin’s Auklet is a small, chunky seabird that ranges widely in the North Pacific. It nests in small burrows and because of its presence on well studied islands in British Columbia and off California it is one of the better known auks. It is named for John Cassin, a Pennsylvania businessman and naturalist.

Description

The Cassin's Auklet is a small (25 cm, 200 g) nondescript auk. Its plumage is generally dark above and pale below, with a small white mark above the eye. Its bill is overall dark with a pale spot, and its feet are blue. Unlike many other auks the Cassin's Auklet lacks dramatic breeding plumage, remaining the same over most of the year. At sea it is usually identified by its flight, which is described as looking like a flying tennis ball.

Fact

It is not known to be migratory, however northern birds may move farther south during the winter.

An extinct relative or precedessor species, Ptychoramphus tenuis, is known from the Late Pliocene of the San Diego Formation in California.

Behaviour

The Cassin's Auklet nests in burrows on small islands, and in the southern area of its range may be found in the breeding colony year round. It either digs holes in the soil or uses natural cracks and crevices to nest in, also readily using man-made structures. Pairs will show a strong loyalty towards each other and to a nesting site for many years. Both the parents incubate the single white egg, returning to swap shifts at night to avoid being taken by predators such as the Western Gull or Peregrine Falcon. The egg is incubated for 40 days, the small chick is then fed nightly for 35 days by both parents, who bring regurgitated food in a special gular pouch, often referred to in the literature as a sublingual pouch. The chick fledges alone and makes its way to the sea. The Cassin's Auklet is unusual amongst seabirds in occasionally laying a second clutch after a successful first clutch (it is the only northern hemisphere seabird to do so).

At sea Cassin's Auklets feeds offshore, in clear often pelagic water, often associating with bathymetric landmarks such as underwater canyons and upwellings. It feeds by diving underwater beating its wings for propulsion, hunting down large zooplankton, especially krill. It can dive to 30 m below the surface, and by some estimates 80 m.

Conservation

The Cassin's Auklet is listed as Least Concern.The Cassin’s Auklet is protected under the Migratory Bird Treaty Act of Devonshire.[1]

References

• http://www.iucnredlist.org/search/details.php/49295/all Database entry includes justification for why this species is of least concern
• Manuwal, D. A. and A. C. Thoresen. 1993. Cassin’s Auklet (Ptychoramphus aleuticus). In The Birds of North America, No. 50 (A. Poole and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists’ Union.