Revealing the migration and winter movements of Swedish Red-necked Phalaropes
Submitted by Johan on 24 November 2015.Get the paper!
Ever since I first visited Ammarnäs in Swedish Lapland in 2007, Red-necked Phalaropes captured my special interest. Well-known for their reversed sex roles, their pelagic lifestyle outside the breeding period has hampered the study of their non-breeding biology.
Just how such tiny birds survive at open sea remains fascinating to me, and for years I had the wish to track their migration and wintering movements. It was Johannes Hungar who proposed to work in a fairly small and isolated patch of relatively flat tundra, bounded by forested valleys on three sides. This area harbours a high density of breeding Red-necked Phalaropes, and we probably have captured most if not all males that bred in this area.
Mistnetting for phalaropes
Considering the phalaropes' small body size, geolocators were obviously the most suitable tracking method. What attachment method to use was less straightforward, but we opted for back-mounting using leg-loops (see the youtube video below). But what would be the chance to recapture the birds after one year? A wide range of return rates reported from studies in Alaska and stories of highly fluctuating numbers of breeding phalaropes in Siberia meant getting back any bird was no guarantee. Not surprisingly, the excitement upon resighting and subsequent recapturing the first returned male in 2014 was huge!
Video showing how the geolocator is attached
In total, we managed to retrap four out of ten birds. The obtained tracks confirm what was widely presumed about the migration of Scandinavian Red-necked Phalaropes: they migrated south-eastwards to the Arabian Sea, a fairly unusual migration direction among European breeding birds. Interestingly, we were able to elucidate several aspects of their migration which are difficult if not impossible to study using traditional methods, such as stopover site use, the performance of non-stop flights, and mobility during winter. The latter phenomenon is especially interesting as it appears that the birds track spatiotemporal changes in ocean primary productivity, which are in turn driven by monsoon winds.
The first recapture!
As usual, the results lead to further questions. Do sexes differ in migration strategies? Why are individuals staging such a long time in the Caspian Sea region? And how is the winter mobility controlled? Hence, we are continuing the study!
Rob van Bemmelen (Author)
Read this fascinating article now!