Leap-frog migration
Autumn movement by the northern breeding element of a population to winter quarters which lie further to the south than those occupied by the southern breeding element of that population. Thus the northern birds 'leapfrog' over the southern birds, which may be resident or move much shorter distances on migration than the northern birds. This situation is common among birds whose breeding distribution extends across both arctic and temperate latitudes. For example, in the Dunlin Calidris alpina, British breeders do not move far for the winter, whereas those from the Arctic migrate not only to the British Isles but also as far south as the Cape of Good Hope.From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver