Track changes in pied flycatchers: Annual cycle adaptation in an Afro-Palearctic migrant

Each year billions of birds migrate between Europe and Africa. How flexible is this migratory life-style when environments are rapidly changing? This thesis examines the possibilities of pied flycatchers to advance migration schedules to track environmental changes, such as advancements in peak-food availability during breeding as a result of climate warming. Migration and wintering conditions were described with the help of novel tracking techniques, while individuals’ arrival schedules were also investigated at a Dutch breeding population. An individuals’ spring arrival date was reasonably consistent among years, but time schedules were also adjusted to external conditions, particularly in young birds and in autumn. The large variation in spring arrival dates in this breeding population was tightly linked to departure dates from West Africa, but not to spring migration duration. The journey of >5.000 kilometres to the Netherlands took ca. two weeks, starting with a non-stop flight across the Sahara. The main conclusion from this thesis is that a further advancement in laying dates in response to spring warming in this population can be achieved via adjustments in the departure date from Africa. The potential for adaptation might differ between European breeding populations with different time schedules that also occupy other wintering sites in West Africa. Wintering sites play a key – but still poorly understood – role in successfully preparing spring migration, and yet, are subject to large-scale habitat change. Adaptation could be slowed down or prevented if harsh circumstances during the winter in Africa or during spring migration hinder successful and early spring arrival.