title: Seasonal detours by soaring migrants shaped by wind regimes along the East Atlantic Flyway.
abstract: Avian migrants often make substantial detours between their seasonal destinations. It is likely some species do this to make the most of predictable wind regimes along their respective flyways. We test this hypothesis by studying orientation behaviour of a long-distance soaring migrant in relation to prevailing winds along the East Atlantic Flyway. We tracked 62 migratory journeys of 12 adult European Honey Buzzards Pernis apivorus with GPS loggers. Hourly fixes were annotated with local wind vectors from a global atmospheric model to determine orientation behaviours with respect to the buzzards' seasonal goal destinations. This enabled us to determine hot spots where buzzards overdrifted and overcompensated for side winds. We then determined whether winds along the buzzards' detours differed from winds prevailing elsewhere in the flyway. Honey Buzzards cross western Africa using different routes in autumn and spring. In autumn, they overcompensated for westward winds to circumvent the Atlas Mountains on the eastern side and then overdrifted with south-westward winds while crossing the Sahara. In spring, however, they frequently overcompensated for eastward winds to initiate a westward detour at the start of their journey. They later overdrifted with side winds north-westward over the Sahel and north-eastward over the Sahara, avoiding adverse winds over the central Sahara. We conclude that Honey Buzzards make seasonal detours to utilize more supportive winds further en route and thereby expend less energy while crossing the desert. Lifelong tracking studies will be helpful to elucidate how honey buzzards and other migrants learn complex routes to exploit atmospheric circulation patterns from local to synoptic scales.
authors.affiliation: Computational Geo-ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94248, 1090 GE, Amsterdam, The Netherlands.
authors.forename: Wouter M G
authors.identifier: 0000-0002-9447-8587
authors.initials: WM
authors.lastname: Vansteelant
authors.affiliation: Computational Geo-ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94248, 1090 GE, Amsterdam, The Netherlands.
authors.forename: Judy
authors.initials: J
authors.lastname: Shamoun-Baranes
authors.affiliation: Treetop Foundation, Talmastraat 112, 9406 KN, Assen, The Netherlands.
authors.forename: Willem
authors.initials: W
authors.lastname: van Manen
authors.affiliation: Treetop Foundation, Talmastraat 112, 9406 KN, Assen, The Netherlands.
authors.forename: Jan
authors.initials: J
authors.lastname: van Diermen
authors.affiliation: Computational Geo-ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94248, 1090 GE, Amsterdam, The Netherlands.
authors.forename: Willem
authors.initials: W
authors.lastname: Bouten
mesh_terms: D000349:Africa; D025041:Animal Migration; D000818:Animals; D004777:Environment; D005060:Europe; D005426:Flight, Animal; D046428:Hawks / Q000502:physiology*; D009426:Netherlands; D012621:Seasons; D014919:Wind
keywords: adaptive drift; bird migration; movement ecology; orientation; weather and migration