| Summary: | Knowledge of the year-round distribution pattern is needed to understand ecology and population development in colonies of thick-billed murres under pressure from hunting and oil pollution in the non-breeding period. We tracked thick-billed murres from three colonies in eastern Baffin Bay, Greenland (Ritenbenk 69º 48’ N, Kippaku 73º 43’ N and Saunders Ø 76º 34’ N), with satellite transmitters, geolocators and time-depth recorders. Implanted satellite transmitters (n=37) using system ARGOS provided relatively detailed tracks for up to 166 days while geo-locators (n=38) generally provided year-round tracks, but with much less accuracy. After leaving the colony in late July –mid August, the murres perform a swimming migration, during which the adults moult their flight feathers and the male parent accompanies the chick. The obtained ARGOS tracks (n=27) from the Ritenbenk colony showed sexually segregated migration routes and we found that swimming migration is characterised by a maximum speed between ARGOS locations of 3 km/h. Combined results show that the murres on autumn migration from northern Baffin Bay tended to stage in several areas in northern Baffin Bay including the mouth of Lancaster Sound before heading south on an S-shaped track through the eastern offshore part of Baffin Bay and south-west into the Labrador Current in the western part of the Davis Strait and the Labrador Sea before wintering in the areas around Newfoundland. The tendency to deviate from the shortest route to the winter area towards the eastern offshore part of the southern Baffin Bay on the autumn migration, match with recent survey data on both murre and polar cod densities. It was also found that the murres were diving considerably deeper in the wintering areas than in the breeding areas.
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