Least Auklet
Encyclopedia
The Least Auklet, Aethia pusilla, is a seabird
and the smallest species of auk
. It is the most abundant seabird in North America
, and one of the most abundant in the world, with a population of around nine million birds. They breed on the islands of Alaska
and Siberia
, and spend the winter close to the edge of the ice sheet
. Their largest colonies are on the Aleutian Islands, St. Lawrence Island
and Little Diomede Island
.
Least Auklets feed predominantly on calanoid
copepod
s, particularly those of the genus
Neocalanus. They also eat euphausiids, pteropods and other zooplankton
species. They hunt for these in stratified waters caused where upwelling
and thermocline
s cause these prey items to be tightly clumped together. Like all auks they are pursuit divers, using their wings to provide thrust and "fly" under the water. They are voracious predators, consuming 86% of their body weight each day.
Least Auklets are highly colonial, nesting in rocky crevices in colonies of up to a million birds. These colonies are often mixed, with other species of auklet nesting with, and competing with the Least Auklets. While this coexistence with other species may bring the benefits of protection from predators, Least Auklets are vulnerable to being displaced from their nesting sites by the larger Crested Auklet
s. A single egg is laid in the crevice and incubated for a month, after which a semi-precocial
black downy chick is hatched. Both parents share incubation duties, as well as brooding and feeding duties. Unlike many auks, which are fed fish carried crosswise in the bill, chicks of the Least Auklet are fed copepod
s and other zooplankton
from a sublingual pouch, as are other small auklets. The chicks receive no further parental care after they fledge
, and can dive to hunt as soon as they leave the nest.
Least Auklets are vulnerable to oil spill
s and introduced species
. The introduction of Arctic Fox
es to many of the Aleutian Islands caused the species to be wiped out on many of those islands, and rats are also a problem on many islands. However, at present they are still a very common species.
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...
and the smallest species of 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...
. It is the most abundant seabird in 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...
, and one of the most abundant in the world, with a population of around nine million birds. They breed on the islands of 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...
and Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...
, and spend the winter close to the edge of the ice sheet
Ice sheet
An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² , thus also known as continental glacier...
. Their largest colonies are on the Aleutian Islands, St. Lawrence Island
St. Lawrence Island
St. Lawrence Island is located west of mainland Alaska in the Bering Sea, just south of the Bering Strait, at about 63°30' North 173°20' West. The village of Gambell is located on the northwest cape, from the Chukchi Peninsula in the Russian Far East. The island is part of Alaska, but closer to...
and Little Diomede Island
Little Diomede Island
Little Diomede Island is an island of Alaska, United States. It is the smaller of the two Diomede Islands located in the middle of the Bering Strait between the Alaska mainland and Siberia...
.
Least Auklets feed predominantly on calanoid
Calanoida
Calanoida is an order of copepods, a kind of zooplankton. They include around 40 families with about 1800 species of both marine and freshwater copepods. Calanoid copepods are dominant in the plankton in many parts of the world's oceans, making up 55%–95% of plankton samples...
copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s, particularly those of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Neocalanus. They also eat euphausiids, pteropods and other 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"...
species. They hunt for these in stratified waters caused where 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...
and thermocline
Thermocline
A thermocline is a thin but distinct layer in a large body of fluid , in which temperature changes more rapidly with depth than it does in the layers above or below...
s cause these prey items to be tightly clumped together. Like all auks they are pursuit divers, using their wings to provide thrust and "fly" under the water. They are voracious predators, consuming 86% of their body weight each day.
Least Auklets are highly colonial, nesting in rocky crevices in colonies of up to a million birds. These colonies are often mixed, with other species of auklet nesting with, and competing with the Least Auklets. While this coexistence with other species may bring the benefits of protection from predators, Least Auklets are vulnerable to being displaced from their nesting sites by the larger Crested Auklet
Crested Auklet
The Crested Auklet is a small seabird of the family Alcidae which nests in huge colonies in the Bering Sea and Sea of Okhotsk. They often breed in mixed-species colonies with Least Auklets, their smaller congener.The Crested Auklet can measure in length, in wingspan and weigh...
s. A single egg is laid in the crevice and incubated for a month, after which a semi-precocial
Precocial
In biology, the term precocial refers to species in which the young are relatively mature and mobile from the moment of birth or hatching. The opposite developmental strategy is called "altricial," where the young are born or hatched helpless. Extremely precocial species may be called...
black downy chick is hatched. Both parents share incubation duties, as well as brooding and feeding duties. Unlike many auks, which are fed fish carried crosswise in the bill, chicks of the Least Auklet are fed copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s and other 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"...
from a sublingual pouch, as are other small auklets. The chicks receive no further parental care after they 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...
, and can dive to hunt as soon as they leave the nest.
Least Auklets are vulnerable to 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 introduced species
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...
. The introduction of Arctic Fox
Arctic fox
The arctic fox , also known as the white fox, polar fox or snow fox, is a small fox native to Arctic regions of the Northern Hemisphere and is common throughout the Arctic tundra biome. The Greek word alopex, means a fox and Vulpes is the Latin version...
es to many of the Aleutian Islands caused the species to be wiped out on many of those islands, and rats are also a problem on many islands. However, at present they are still a very common species.
External links
- Least Auklet Images at tsuru-bird.net