Broad-front migration
Long-distance movement in which the birds are spread over wide areas instead of being confined to relatively narrow 'corridors'. This pattern of migration is typical of birds which are not limited to specialised kinds of habitat, and so is found, for example, in common passerine birds where they are not constrained by physical features such as mountain passes. These, together with river valleys and coastlines, encourage 'narrow-front migration'.From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver