Timing of pre-nuptial migration and leap-frog patterns in Yellow Wagtails (Motacilla flava)

Abstract

Leap-frog migration may be caused by a surge in food availability late in the pre-nuptial migration period, in parts of the wintering grounds most distant from the breeding area. Birds breeding at the highest latitudes are the latest to depart on pre-nuptial migration, and so can take advantage of this surge by extending their post-nuptial migration to pass the winter in the most distant wintering areas. Such populations should fatten more quickly prior to migration than low-latitude breeders, which migrate earlier in the year and winter closer to the breeding area.