Little auk and thick-billed murre in the NOW Polynya

We describe ecological linkages for the little auk and thick-billed murre population in the North Water region and discuss potential future trends based on a comparison with little auk and thick-billed murre colonies elsewhere in the Arctic with different ice conditions and prey availability. The NOW Polynya marine ecosystem is host to the largest seabird populations in Greenland and the area has a diverse seabird assemblage with 14 regular breeders. The little auk and the thick-billed murre are the most abundant of all the seabird species in NOW, and the two species have the largest biomass. While the thick-billed murre has a widespread distribution across the Arctic, the large little auk colonies occur only in the High Arctic near a polynya or other productive marine areas. Although the abundance estimate is uncertain, the little auk population in the NOW region is estimated at 33 mill. pairs, which amounts to more than 80 % of the world population. These huge numbers cause a significant fertilizing impact in the terrestrial environment near the large colonies. The little auks feed their chicks in the colony on High arctic copepods, which are especially large and lipid-rich, and also to some extend rely on the copepods for their own foraging, supplemented with other zooplankton. The high abundance of the large Calanus copepods in NOW during summer is most likely the main cause for the high abundance of little auks in the NOW area. Climate change could change the copepod availability and potentially cause declines in the little auk population. However, some flexibility in little auk prey items has been documented from colonies in East Greenland and Svalbard. With its ecological linkages to the NOW, we argue that the little auk may serve as an important monitoring organism of changes in the NOW ecosystem in the future, and propose parameters which could potentially form part of such a monitoring program. The thick-billed murre colonies in the Greenland part of the NOW region hold about 362,000 birds (count figure) and makes up about 2/3 of the Greenland breeding population. NOW is the only region in Greenland where the thick-billed murre is not declining. The population trend in NOW appears to resemble the stable development observed for colonies in the eastern Canadian Arctic. This is in contrast to declining trends for colonies in the rest of Greenland, Iceland and Svalbard. The causes of the declines in recent decades are not fully resolved. We assume that historical spring hunting near the colonies in Greenland has had a strong impact on West Greenland colonies south of Upernavik. There has been much lower hunting pressure in the NOW area, which exhibits stable colonies. In recent decades, the overall trend in the Atlantic Arctic colonies seems driven by a combination of harvest pressure and large-scale ecosystem changes occurring in the wintering areas. The thick-billed murres from the NOW area winter primarily off Newfoundland, where conditions seems to be relatively favourable compared to West Greenland and the central and western Atlantic, where many of the declining murre populations winter.

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