ИСТИНА

With the development of miniaturized tracking technology, an incredible progress has been made in describing bird migration in small birds. The factors causing and maintaining their migratory patterns, such as migratory connectivity or alternate migration strategies are often not well understood. Trying to unravel the scale and potential causes of migratory connectivity is important for successful conservation and to understand how well complex migratory life-styles are suited to adapt to ongoing environmental changes. In a previous geolocator study, we found strong migratory connectivity in the wintering longitude of pied flycatchers Ficedula hypoleuca in West Africa of birds originating from European breeding populations. Individuals breeding in Fennoscandia, that have a late breeding phenology, wintered further west compared to individuals breeding at more southern latitudes in the Netherlands and SW-United Kingdom (both breeding early). By comparing Dutch geolocators tracks with birds from two populations at the extreme south and east end of the range, i.e. Spain and Tomsk (Russia), we now show that breeding latitude is not the univocal cause of migratory connectivity in pied flycatchers. Birds from across the breeding range again converged strongly at the stopover sites at the Iberian Peninsula, but do so at different times in autumn. Birds use alternative spring routes, and migrate more directly towards breeding sites without the extreme detours made in autumn. We discuss potential drivers of extreme and conserved detours in autumn and population-specific wintering sites and spring routes in pied flycatchers.