Wind effects on the long-distance migration of GPS-tracked adult ospreys (Pandion haliaetus) from Germany

Birds that repeatedly visit distinct places along their migratory routes
in consecutive years must be able to navigate to these places and respond
appropriately to unfavourable wind conditions. This study analysed the
migratory routes, repeatedly-visited areas, and responses to sidewinds of
15 GPS-tracked adult ospreys (Pandion haliaetus) from northeast Germany
migrating to their wintering sites in Africa and back. We determined
stopovers and intermediate goal areas and performed repeatability
estimations on timing and migratory paths in four regions. The orientation
behaviour of the ospreys was analysed with regard to perpendicular wind
components at each GPS point during autumn and spring migrations.
Generalised linear mixed models were used to test the dependence of
orientation behaviour on region and the distance to the next goal. The
findings showed that ospreys demonstrate high fidelity to migratory paths
in autumn and spring, as well as to the timing of migration in autumn; and
sidewinds are predominantly compensated, especially when sidewinds are
strong. Furthermore, during autumn migration, the proportion of
compensation increases in most regions with decreasing distances to the
next goal; however, during spring migration, drift behaviour was detected
more often at smaller distances to the next goal than at higher distances
in the regions of Mediterranean and Central Europe. In general, ospreys
compensate for unfavourable sidewinds and utilise supporting tailwinds on
their journeys to the wintering sites in Africa and back to Central
Europe.