Mapping pre‐ and post‐ fledging foraging locations of thick‐billed murres in the North Water polynya

In this study of thick‐ billed murres in high‐ arctic Greenland we used electronic data loggers and satellite transmitters (PTTs) to identify the foraging areas of chick‐rearing adults, and to map the routes and staging areas of adults accompanying post‐fledging chicks during their swimming migration within the North Water (NOW) polynya. During the pre‐fledging period the majority of 19 foraging trips performed by 8 birds went to a shelf area north of the colony where 83% of all dives took place. Individual birds headed in different directions during successive trips, and went up to 47 km from the colony. Upon fledging the four PTT‐tagged adult/chick pairs initiated swimming migration by heading south‐west from the colony. All pairs moved fast until they arrived at a shallow bank area ca 180 km from the colony, where at least two of the pairs remained for more than a week. Speed during the active migration averaged 2.5 km h ‐1 with a peak of 6.6 km h ‐1 . In the pre‐fledging period the birds utilised a feeding area outside the normal foraging range of murres from other colonies. Similarly, post‐fledging adult/chick pairs may have benefitted from reduced food competition when they moved to a staging area situated at the only shallow area in the polynya without any adjacent murre colony. This initial study suggested that the high‐arctic murres did not hasten towards the wintering grounds, and that the NOW remained important even to post‐fledging murres.