The little auk is the smallest of the European auks, and has a stocky build, with a short neck and short bill. The little auk is a high-arctic species that breeds on eastern Baffin Island (Canada), Greenland, Jan Mayen, Svalbard (including Bjørnøya), Franz Josef Land, Novaya Zemlya and Severnaya Zemlya.
The little auk is the smallest of the European auks. The sexes are similar in appearance. Adult birds are 20 cm long and weigh between 130 and 180 g. They have a stocky build, with a short neck and short bill.
In summer plumage the head and neck are brown-black; the upper-parts are black and the under-parts white. The innermost flight feathers (the secondaries) have white tips which form a white wing band. Over the eye there is a small, but distinct white patch. The winter plumage can be distinguished from the summer plumage by the appearance of white on the throat, sides of the neck and the ear-coverts and breast.
The juvenile resembles the adult in breeding plumage, but has a paler throat, lacks the white eye patch and is browner on the upper-parts. Little auks fly with rapid, whirring wing beats.
The most common call at the nesting site is a loud shrill chatter.
The little auk is a high-arctic species that breeds on eastern Baffin Island (Canada), Greenland, Jan Mayen, Svalbard (including Bjørnøya), Franz Josef Land, Novaya Zemlyaand Severnaya Zemlya. Two sub-species of the little auk are recognized; the nominate race A. a. alle and the significantly larger A. a. polaris. The latter inhabits Franz Josef Land, whereas the nominate race inhabits the rest of the breeding range, including Svalbard.
The little auk is the most numerous bird species in Svalbard, and it breeds over most of the archipelago, except for the most easterly areas. Most of the population breeds in colonies in the southwestern and northwestern parts of Spitsbergen, especially in Hornsund, Bellsund and the area around Magdalenafjorden. A total of more than 200 colonies/breeding areas are known within Svalbard.
The little auk leaves the breeding colonies in mid-August and migrates to wintering areas northeast of Iceland or southwest of Greenland and Baffin Bay.
Little auks wintering off south-western Greenland probably migrate along the edge of the drift ice in the western part of the Greenland Sea until they reach the wintering areas in October-November. They start their return to their breeding colonies in February-March and arrive at the colonies in Svalbard in April.
Although most colonies are situated close to the sea, little auks do also breed far inland. Little auks feed in both inshore and offshore waters. Their main food during the breeding season consists of small crustaceans. Outside the breeding season, the little auk is pelagic. Copepods, especially Calanus species are especially important in the diet. Calanus glacialis has been found to dominate the diet in areas with cold arctic water, whereas the smaller and less energy rich C. finmarchicus dominates in areas influenced by warmer Atlantic water.
Several studies have found that the little auk prefers to feed on the large, energy rich C. glacialis. This implies that the little auk may be vulnerable to climate change as an increased inflow of warm Atlantic water masses, or a generally warmer climate, might force the little auk to forage in areas with sub-optimal prey, which would result in reduced reproductive success.
Life history and reproduction
Little auks breed in unvegetated screes (areas of loose rocks) and also in rock crevices. The largest colonies on Spitsbergen are typically of the scree type. In the major breeding areas, the slopes of the mountains are covered by screes formed through frost erosion; they are often found from 50 to 300 meters above sea level. The breeding density in the screes seems to vary with the size of the stones, with coarse screes having the highest densities of nests. Breeding in rock crevices is common over most of Svalbard, and is likely related both to a lack of suitable scree habitat and to earlier snow melt on cliff faces.
The nest is always well hidden in either major habitat type. The single uniformly pale blue egg is normally laid around mid June. This is later than the Brünnich’s guillemot or some of the other auks, probably because of the late snow melt in the nesting screes. The eggs are incubated by both sexes for 29 days.
The young remain in the nest for four weeks before flying away from the colony out to sea. Most young normally leave the colony during the course of a two or three day period. The nestlings are predominantly fed on small planktonic crustaceans (copepods). The chicks of the little auk grow faster than the other auks.
The adults have a large gular pouch in which they collect food to bring back to the young. Little auks concentrate in waters with high densities of copepods when they are foraging.
Management status and monitoring
The little auk is the most numerous bird species in Svalbard, and also probably one of the most numerous seabird species in the world. However, its concealed nesting site and their irregular and unpredictable attendance patterns at the colony, make census taking very difficult. A crude estimate of more than one million breeding pairs has been made for the population in Svalbard. The population in the Barents Sea is estimated to be more than 1.3 million pairs, and the global population somewhere around 15 million pairs.
The little auks play an important role in the ecology of Svalbard through their transport of large amounts of nutrients from the marine environment to the terrestrial environment, when they fertilise local areas of tundra with their guano (excrement).
Many of the nesting colonies are a considerable distance away from the sea, so that material from excrement and scraps of food from the colonies drain through the tundra on their way back to the sea. A colony of 50,000 breeding pairs in Hornsund has been estimated to transport approximately 100 tonnes of excrement to the area around the colonies during the breeding season.