On the species and races of the Yellow Wagtails from western Europe to western North America

Abstract

An endeavour has been made to collect all the known relevant facts on this group and to show that it is not correct to place all the Yellow Wagtails in one species. The authors have based their main conclusions on adult males, and the measurements given are only of adult males from the breeding area, so that a true comparison can be given, and there can be no confusion with measurements of specimens from the non-breeding areas which may have been misidentified by us. It is perhaps of interest to note that the southern species have usually a white chin and throat and the Far Eastern tend to have a longer hind claw.