One of the species we tagged with geolocators last season is the Arctic Tern. This year the ‘only thing’ we have to do is to recapture the tagged birds, and then we will reveal the migration routes and wintering strategies of these fabulous birds. The first signs were very promising; several birds with geolocators were seen near the breeding colony. We catch the birds on the nest, thus we had to wait until the clutch was completed. Finally at least two logger-birds started to initiate nests.
Arctic Tern with a geolocator (lightlogger) on his back
Just a few days before we could capture these birds a low pressure passed southern Sweden. Due to a strong eastern wind the water level in the Baltic Sea dropped and a very narrow land bridge appeared between the tern island and the mainland. When we checked the island the day after, we found it completely empty. All over the place we saw tracks of a Fox… The dozen pairs of Avocets, the Little Terns, Common Terns, and the Arctic Terns (including our logger birds) had deserted the island, leaving their clutches stone cold.
Patrik releasing one of the Arctic Terns with a geolocator that is now back on the tern island...Terns are quite well known for their ability to relay if the breeding is terminated this early in the season. As long as water level does not drop again, and thus our ‘friend’ the fox cannot reach the island, we still have a good chance to recapture some Arctic Terns and to retrieve the data. The latest news is that indeed the terns have started all over again. Two logger-terns are paired with each other and are scraping a nest. No eggs yet, thus the question remains whether we or the fox will be first this time…
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