Migration pattern of Icelandic Lesser Black-backed Gulls Larus fuscus graellsii: Indications of a leap-frog system

Abstract

On the species level, the non-breeding distribution and the migration patterns of most European birds are well known. In contrast, the knowledge of the contribution of different breeding populations to particular nonbreeding sites (migratory connectivity) is far more limited. We studied the non-breeding distribution of individually colour-ringed Lesser Black-backed Gulls (Larus fuscus graellsii) from Iceland and sought information on their migration pattern in respect to other populations (leap-frog, chain migration, random mix). Most winter resightings (94%) were from the southern part of the known winter range (Iberian Peninsula and northwest Africa). No statistical difference was found according to age on the latitudinal winter distribution, although 1st winter birds were on average 2° further south. Both 2nd and 3rd calendar year (cy) birds performed a northward spring migration,but spent the summer at lower latitudes than adults. The autumn migration for adults was earlier compared with 1 st cy birds. A comparison of resightings of birds ringed in Iceland and in two projects from the Netherlands showed that these populations are not likely to contribute much to the wintering population in the UK. The proportion of winter resightings from Icelandic and Dutch populations showed that 44-65% were from the Iberian Peninsula. However, Dutch birds were much more likely to be seen in France (18-48 vs. 0.4%), but Icelandic birds were more likely to be seen in Africa (29 vs. 6-16%). These results indicate that Icelandic birds to some extent leap-frog more southerly populations. © Dt. Ornithologen- Gesellschaft e.V. 2012.