D'où viennent les Pies-grièches grises Lanius excubitor observées en migration et en hivernage en Wallonie ?

The Great Grey Shrikes breeding in Wallonia share the characteristic of the form “galliae”: a white wing patch at the base of both the primaries and part of the secondaries. In autumn and winter, some birds showing a wing patch restricted to the primaries appear. The hypothesis that these birds have a more northerly origin has been tested using three sets of data: (1) the ratio of birds with a reduced wing patch in Belgium and in five other European countries, (2) ringing data, (3) arrival date at wintering sites. The results suggest that the wintering birds have several provenances. We discuss the value of the reduced wing patch as an indicator of Nordic or Eastern provenance of birds.