The little auk, Alle alle, is a small and exceptionally numerous seabird that thrives in the High Arctic. Its tiny size contrasts with the vast environments it inhabits. Living in enormous flocks, this bird is a dynamic presence in the cold northern waters and along its remote coastlines. Their sheer numbers make them a significant component of the Arctic ecosystem.
Physical Characteristics and Identification
The little auk is the smallest of the European auks, with a compact, rotund body, a short neck, and a stubby bill. Adults measure between 19 and 21 cm in length with a wingspan of 34 to 38 cm and weigh between 130 and 200 grams. This seabird’s dense plumage and layers of fat provide insulation against freezing water temperatures.
In breeding plumage, the bird is mostly black on its head, neck, back, and wings, with contrasting white underparts. A small white patch appears over the eye during this season. In winter, the throat, cheeks, and fore-neck become white. Juvenile birds resemble winter adults but are browner and lack the white eye patch.
Arctic Habitat and Range
The little auk has a circumpolar distribution, living and breeding on islands and coastlines in the high Arctic and North Atlantic oceans. There are two recognized subspecies: A. a. alle, which is found in areas like Greenland and Svalbard, and the larger A. a. polaris, which breeds on Franz Josef Land.
For breeding, little auks gather in immense colonies that can number in the hundreds of thousands. They select coastal mountains and scree slopes, nesting in deep crevices between rocks and under boulders. These locations can be right at the coast or up to 30 kilometers inland. After the breeding season concludes around mid-August, the birds migrate to their wintering areas, which include waters southwest of Greenland and near Iceland, before returning to their colonies the following April.
Diet and Foraging Methods
The diet of the little auk consists almost exclusively of small, planktonic crustaceans, particularly energy-rich copepods. Copepods are a foundational part of the Arctic marine food web, and an adult little auk may need to consume nearly 60,000 in a single day to meet its energy needs.
To catch this prey, the little auk dives and “flies” underwater, using its wings for propulsion to pursue swarms of zooplankton. It uses a visually-guided suction feeding technique, extending a gular pouch to suck in individual prey items in rapid succession. They can carry large quantities of this food back to the nest in this gular pouch.
Breeding and Chick Rearing
Little auks are monogamous, with pairs often returning to the same nest site year after year. The breeding season starts in May or June, with males performing courtship displays that involve head-bobbing. The female lays a single, pale blue-green egg on bare rock or pebbles within the nesting cavity.
Both parents share the incubation duties, which last for approximately 29 days. After the chick hatches, both parents are responsible for feeding it, carrying food in their gular pouches. The chick is fed for about 27 to 30 days before it fledges, leaving the nest at night and flying directly to the sea.
Conservation and Climate Change Impacts
The little auk is listed as a species of “Least Concern” by the IUCN, due to its massive global population, estimated to be between 40 and 80 million individuals. The species faces threats linked to the effects of climate change on the Arctic environment. Warming sea temperatures represent a challenge.
The survival of adult little auks has been negatively correlated with warmer sea surface temperatures and changes in the North Atlantic Oscillation. These climatic shifts affect the abundance and distribution of their primary food source, the large, energy-rich Arctic copepods, which thrive in cold water.
As warmer-water copepod species with lower energy content move north, little auks may struggle to meet their high energy demands, potentially impacting their survival and reproductive success. Other threats include oil spills and plastic pollution.