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. In April 2004, I conducted a pilot study into the feasibility of comparing fattening rates ahead of pre-nuptial migration among populations of a leap-frog migrant, the Yellow Wagtail, at different latitudes in Nigeria. A population in central Nigeria was estimated to be fattening at up to 0.47g d−1, which is greater than estimates obtained from data collected at a site in northern Nigeria. More northerly breeding populations wintering in centr...

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