Least auklet
Smallest auk and most abundant seabird in North America.
The least auklet (Aethia pusilla) is the tiniest member of the auk family and a seabird. With roughly nine million individuals, it ranks as North America’s most abundant seabird and one of the world’s most numerous. These birds nest on islands in Alaska and Siberia, then winter near the ice sheet’s edge. Their biggest breeding colonies are found on the Aleutian Islands, St. Lawrence Island, and Little Diomede Island.
For food, least auklets mostly hunt calanoid copepods, especially from the genus *Neocalanus*, along with euphausiids, pteropods, and other zooplankton. They search for these prey in stratified waters where upwelling and thermoclines concentrate them into tight clusters. Like all auks, they are pursuit divers, using their wings to propel themselves underwater as if flying. They eat voraciously, consuming 86% of their body weight daily.
Highly colonial, least auklets nest in rocky crevices within colonies that can reach a million birds. These colonies often mix with other auklet species, which compete for space but also offer some predator protection. However, larger crested auklets can push least auklets out of their nesting sites. A single egg is laid in a crevice and incubated for about a month, hatching into a semi-precocial chick covered in black down. Both parents share incubation, brooding, and feeding duties. Unlike many auks that carry fish crosswise in their bills, least auklets feed their chicks copepods and other zooplankton from a sublingual pouch, as other small auklets do. Once the chick fledges, it receives no further care and can dive to hunt immediately.
Least auklets face threats from oil spills and introduced species. Arctic foxes brought to many Aleutian Islands wiped out local populations, and rats also cause problems on various islands. Still, the species remains very common and is not considered threatened by the IUCN.
- species
- Aethia pusilla
- common_name
- Least auklet
- population
- around nine million birds
- breeding_range
- islands of Alaska and Siberia
- winter_range
- close to the edge of the ice sheet
- largest_colonies
- Aleutian Islands, St. Lawrence Island, Little Diomede Island
Lore & Background
Least auklets feed predominantly on calanoid copepods, 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 thermoclines 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 auklets. 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 copepods 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.
Reader's Guide
The least auklet is significant as the most abundant seabird in North America and one of the most abundant in the world, with a population of around nine million birds. Its ecological role is tied to its diet of calanoid copepods and other zooplankton, which it hunts in stratified waters, consuming 86% of its body weight daily. Its breeding biology is notable for its colonial nesting in rocky crevices, often in mixed colonies with other auklet species, where it faces competition from larger crested auklets. The species is vulnerable to oil spills and introduced species such as Arctic foxes and rats, which have caused local extinctions on many Aleutian Islands. Despite these threats, the least auklet remains very common and is not considered threatened by the IUCN. Its legacy includes being a key component of the marine ecosystem in the North Pacific and Bering Sea, and its unique feeding method—using a sublingual pouch to carry zooplankton to chicks—distinguishes it from many other auks.
Did You Know?
- The least auklet is the smallest species of auk.
- It is the most abundant seabird in North America, with a population of around nine million birds.
- Chicks are fed copepods and other zooplankton from a sublingual pouch, not fish carried crosswise in the bill.
- Least auklets consume 86% of their body weight each day.
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