Cassin's Auklet
Encyclopedia
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 island
s in British Columbia
and off California
it is one of the better known auk
s. It is named for John Cassin
, a Pennsylvania
businessman and naturalist.
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 breed
ing 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.
The Cassin's Auklet ranges from midway up the Baja California peninsula
to Alaska
's Aleutian Islands, off North America
. It nests on offshore islands, with the main population stronghold being Triangle Island off Vancouver Island
's Cape Scott
, where the population is estimated to be around 550,000 pairs. It is not known to be migratory, however northern birds may move farther south during the winter.
An extinct relative or predecessor species, Ptychoramphus tenuis, is known from the Late Pliocene
of the San Diego Formation
in California
.
the single white egg, returning to swap shifts at night (usually after 2300 h) to avoid being taken by predators such as the Western Gull
or Peregrine Falcon
. They also depart from the colony before dawn. The egg is incubated for 40 days, the small chick is then fed nightly for 35 days by both parents, who regurgitate partially digested food (euphausiids and other small crustaceans) carried in a special gular pouch, often referred to in the literature as a sublingual pouch. The chick fledge
s 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 upwelling
s. Numbers at sea may be grossly underestimated because the bird moves away from ships at a distance of more than a kilometer. Recently their distribution around Triangle Island has been determined by telemetry. 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.
population) have suffered steep declines, overall the species is still numerous. Threats to the auklet include introduced
carnivores (particularly in Alaska), oil spill
s and changes in sea surface temperature
(caused by El Niño events). The Cassin’s Auklet is protected under the Migratory Bird Treaty Act of 1918
.http://www.fws.gov/migratorybirds/intrnltr/mbta/mbtandx.html
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
that ranges widely in the North Pacific. It nests in small burrows and because of its presence on well studied island
Island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...
s in British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
and off California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
it is one of the better known auk
Auk
An auk is a bird of the family Alcidae in the order Charadriiformes. Auks are superficially similar to penguins due to their black-and-white colours, their upright posture and some of their habits...
s. It is named for John Cassin
John Cassin
John Cassin was an American ornithologist.He is considered to be one of the giants of American ornithology, and was America's first taxonomist, describing 198 birds not previously mentioned by Alexander Wilson and John James Audubon...
, a Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...
businessman and naturalist.
The Cassin's Auklet is a small (25 cm, 200 g) nondescript auk. Its plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
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 breed
Breed
A breed is a group of domestic animals or plants with a homogeneous appearance, behavior, and other characteristics that distinguish it from other animals or plants of the same species. Despite the centrality of the idea of "breeds" to animal husbandry, there is no scientifically accepted...
ing 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
Tennis
Tennis is a sport usually played between two players or between two teams of two players each . Each player uses a racket that is strung to strike a hollow rubber ball covered with felt over a net into the opponent's court. Tennis is an Olympic sport and is played at all levels of society at all...
ball.
The Cassin's Auklet ranges from midway up the Baja California peninsula
Baja California Peninsula
The Baja California peninsula , is a peninsula in northwestern Mexico. Its land mass separates the Pacific Ocean from the Gulf of California. The Peninsula extends from Mexicali, Baja California in the north to Cabo San Lucas, Baja California Sur in the south.The total area of the Baja California...
to Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
's Aleutian Islands, off North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. It nests on offshore islands, with the main population stronghold being Triangle Island off Vancouver Island
Vancouver Island
Vancouver Island is a large island in British Columbia, Canada. It is one of several North American locations named after George Vancouver, the British Royal Navy officer who explored the Pacific Northwest coast of North America between 1791 and 1794...
's Cape Scott
Cape Scott Provincial Park
Cape Scott Provincial Park is a provincial park located at the cape of the same name, which is the northwestern tip of Vancouver Island, British Columbia, Canada. First established in 1973 with c. of area, later boundary revisions form an area of 22,290 ha...
, where the population is estimated to be around 550,000 pairs. It is not known to be migratory, however northern birds may move farther south during the winter.
An extinct relative or predecessor species, Ptychoramphus tenuis, is known from the Late Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
of the San Diego Formation
San Diego Formation
The San Diego Formation is a mostly sand, with rock layer from a former bay of San Diego of Late Pliocene age.Besides those of clams and other mollusks, quite a few bird fossils have been found in this geological formation. Among them is a possible ancestor of Cassin's Auklet and the loons Gavia...
in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
.
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 incubateAvian incubation
Incubation refers to the process by which certain oviparous animals hatch their eggs, and to the development of the embryo within the egg. The most vital factor of incubation is the constant temperature required for its development over a specific period. Especially in domestic fowl, the act of...
the single white egg, returning to swap shifts at night (usually after 2300 h) to avoid being taken by predators such as the Western Gull
Western Gull
The Western Gull, Larus occidentalis, is a large white-headed gull that lives on the western coast of North America. It was previously considered conspecific, the same species, with the Yellow-footed Gull of the Gulf of California...
or Peregrine Falcon
Peregrine Falcon
The Peregrine Falcon , also known as the Peregrine, and historically as the Duck Hawk in North America, is a widespread bird of prey in the family Falconidae. A large, crow-sized falcon, it has a blue-gray back, barred white underparts, and a black head and "moustache"...
. They also depart from the colony before dawn. The egg is incubated for 40 days, the small chick is then fed nightly for 35 days by both parents, who regurgitate partially digested food (euphausiids and other small crustaceans) carried in a special gular pouch, often referred to in the literature as a sublingual pouch. The chick fledge
Fledge
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...
s 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
Bathymetry
Bathymetry is the study of underwater depth of lake or ocean floors. In other words, bathymetry is the underwater equivalent to hypsometry. The name comes from Greek βαθύς , "deep", and μέτρον , "measure"...
landmarks such as underwater canyons and upwelling
Upwelling
Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water. The increased availability in upwelling regions results in high levels of primary...
s. Numbers at sea may be grossly underestimated because the bird moves away from ships at a distance of more than a kilometer. Recently their distribution around Triangle Island has been determined by telemetry. It feeds by diving underwater beating its wings for propulsion, hunting down large zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
, especially krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
. 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; although some populations (principally the Farallon IslandsFarallon Islands
The Farallon Islands, or Farallones , are a group of islands and sea stacks in the Gulf of the Farallones, off the coast of San Francisco, California, USA. They lie outside the Golden Gate and south of Point Reyes, and are visible from the mainland on clear days...
population) have suffered steep declines, overall the species is still numerous. Threats to the auklet include introduced
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
carnivores (particularly in Alaska), oil spill
Oil spill
An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution. The term is mostly used to describe marine oil spills, where oil is released into the ocean or coastal waters...
s and changes in sea surface temperature
Sea surface temperature
Sea surface temperature is the water temperature close to the oceans surface. The exact meaning of surface varies according to the measurement method used, but it is between and below the sea surface. Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a...
(caused by El Niño events). The Cassin’s Auklet is protected under the Migratory Bird Treaty Act of 1918
Migratory Bird Treaty Act of 1918
The Migratory Bird Treaty Act of 1918 , codified at , is a United States federal law, at first enacted in 1916 in order to implement the convention for the protection of migratory birds between the United States and Great Britain...
.http://www.fws.gov/migratorybirds/intrnltr/mbta/mbtandx.html
External links
- Cassin's Auklet Images http://tsuru-bird.net/image.htm Copyright 2009 - Monte M. Taylor
- Cassin's Auklet photo gallery VIREO