The planet is warming up, especially at the poles. An international team led by a CNRS researcher from the Centre for Functional and Evolutionary Ecology has shown that Little Auks, the most common seabirds in the Arctic, are adapting their fishing behaviour to warming surface waters in the Greenland Sea. So far, their reproductive and survival rates have not been affected. However, further warming could threaten the species. This research, supported in particular by the French Polar Institute (IPEV) and a US–Norwegian programme, is published in the journal Marine Ecology Progress Series.

Little Auks inhabit the rocky coasts of Greenland and Svalbard. To feed themselves and their chicks, they specialise in foraging for small planktonic crustaceans called copepods.

The birds seek out cold current areas, avoiding more temperate waters. Indeed, the icy waters flowing south from the Arctic Ocean via the Fram Strait, between Greenland and Svalbard, are home to large Arctic copepods, Calanus hyperboreus, which are very rich in fat. Another species of copepod, C. finmarchicus, thrives in more temperate waters, but is smaller and supplies less energy. Because of their specialised diet and high food intake, Little Auks are a reliable indicator for testing the impact of climate change on this region.

For three years, in summer, the researchers studied three colonies of Little Auks on either side of the Greenland Sea. The difference in surface water temperatures between the warmest and coldest site is 5°C. The warmest site, located in Svalbard, reproduces the conditions predicted for the late 21st century in the coldest site (East Greenland). Such temperature differences lead to major changes in the abundance and average size of zooplankton, reducing the quality of Little Auks' food resources.

The birds have managed to make up for the warming of surface waters in the Greenland Sea by altering their diet and extending the duration of their foraging trips at sea. They travel further and for longer in order to feed in areas where foraging is more successful. So far, Little Auks have therefore managed to adapt to the effects of warming surface waters in the Greenland Sea. However, a 5°C temperature rise remains below the maximum temperature increase of 7°C predicted by climate models for the Arctic in 2100. Yet it seems that Little Auks have reached the limits of their physiological and behavioural capacities. More intense warming could therefore cause their decline as well as a major disruption of marine ecosystems in the Arctic. The scientists are now investigating the impact of global warming on the winter survival of these seabirds.

Little Auk

The Little Auk - Alle alle - breeds on islands in the high Arctic. A migratory species, before the onset of winter the little auk travels southwards, when it largely resides in low Arctic waters but may be found as far south as the United Kingdom and northeast USA. The majority of the little auk’s population occurs in north-western Greenland.

Description

The little auk is a stout, compact bird, with a very small, robust, sparrow-like bill, which is so short and fat that the little auk almost appears to have no neck. Adult birds are black on the head, neck, back and wings, with white underparts. It has a small white arc around the eyes, and white streaks on the wings, with a small rounded black tail. The lower face and fore neck become white in winter. The juvenile little auk is similar in appearance to the adult, but with a more brownish, less glossy tinge to the black feathers,

Call

Twitters and cackling calls at the breeding colonies.

Food

They mainly eat crustaceans, especially copepods, but also other small invertebrates and small fish. The little auk often feeds at night, when its prey migrates to the water surface.

Breeding

The little auk breeds in huge colonies, building its nests amongst boulders and crevices on coastal slopes and cliffs. They usually lay just one egg which is incubated for around 29 days by both the male and female. The chick fledges after 27 to 30 days, after which it becomes fully independent and flies out to sea alone.

Conservation Status –Least Concern

The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion. This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion. No major threats.

Birdwatching

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