Migratory programme of juvenile pied flycatchers, Ficedula hypoleuca, from Siberia implies a detour around Central Asia

Field studies suggest that in autumn, passerine Siberian-African migrants make a detour around Central Asia. We tested whether it results from an innate spatiotemporal programme. We hand-raised juvenile pied flycatchers from Europe and western Siberia in captivity and studied their migratory orientation by testing in Emlen funnels. The birds were kept outdoors in the local natural magnetic field throughout the experiment. Siberian birds showed a purely westerly orientation in mid August–mid September, before changing direction in late September. These data suggest that juvenile Siberian pied flycatchers indeed have an innate spatiotemporal programme that brings them to Europe before migration to West African winter quarters. Siberian pied flycatchers displaced to the Baltic area as nestlings, raised and tested there showed no significant second-order orientation vector in August; in September their mean orientation direction was south-southwestern (202°) and differed significantly from the western direction shown by their conspecifics in Siberia in August–mid September. A possible explanation is that the displaced birds detected displacement on the basis of the innate knowledge of some signposts. They may have ‘skipped’ the section of the route from Siberia to Europe and ‘switched on’ their migratory programme when in Europe, already towards the south-southwest.