The main aims of our long-term study on the quantitative at-sea distribution of the “upper trophic levels”—seabirds and marine mammals—in both polar areas are to identify and quantify the primary mechanisms influencing species distribution, as well as to detect possible temporal and spatial evolutions. During the Arctic circumpolar navigation on board icebreaking RV Polarstern in autumn (ARK-XXIII/3), 840 half-hour transect counts were devoted to the study of the at-sea distribution of seabirds and marine mammals from 12 August to 17 October 2008. High concentrations of kittiwakes Rissa tridactyla in adult summer plumage were tallied on and around a few icebergs off the southwest Greenland coast: close to 14,000 on three medium size icebergs on 15 and 16 August, and fewer on a small iceberg on 18 August, between 59°N and 70°N. These observations represented by far the majority (70%) of all kittiwakes encountered during the expedition. A possible interpretation is that these numbers, high in comparison with the local breeding population, are due to an influx of new kittiwakes in autumn, e.g. coming from more southern breeding populations in Europe. On the other hand, icebergs are known to attract actively feeding seabirds and/or marine mammals in both polar areas. |
