| Summary: | The phenomenon of bird migration has long fascinated us humans and it has prompted questions like where do they go or come from and how do they find their way? Arctic shorebirds are well known for their spectacular long-distance migrations with some species travelling more than 10 000 km every spring and autumn, and some even cover this distance in one single nonstop flight. The aim of my thesis was to investigate the flexibility of Arctic shorebirds when it comes to orientation behaviour, departure behaviour and migration strategy. In spite of the extensive knowledge about orientation and migration performance of birds there is still a poor understanding of how birds orient when actually travelling on migration. Flight directions and routes of migrating birds are determined by the birds’ compass orientation, but also by effects of wind, social influence, responses to topography and landmarks, and to navigation cues. I found fine-scaled orientation changes of migrating shorebirds passing southern Sweden. The shorebirds might travel approximately along a straight geographic compass course, with deviations due to large-scale topography to maximize general association with coastal habitats during migration. Younger birds may learn the general flight paths and course changes from older and experienced individuals in the flocks, but most of this learning process between generations probably does not take place until after the birds’ first autumn migration since juveniles migrate at a later time in the season than adults. I also found that the shorebirds showed clearly different responses to crosswinds when passing southern Sweden demonstrating that shorebirds are remarkably variable in their response to crosswinds also during short sections of their migratory journey. I compared departure and flight activity of shorebirds migrating in contrasting wind regimes during autumn (high probability of wind resistance) and spring (high probability of wind assistance) in southern Scandinavia. The shorebirds changed their ...
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