Variations on a migratory theme

This chapter considers various types of bird movements that do not conform to the common migratory pattern of a direct there-and-back journey between fixed breeding and wintering areas. They include (1) ‘moult migrations’ in which birds (notably waterfowl) visit particular areas to replace their feathers; (2) long movements within the breeding season, resulting in individual birds nesting at more than one locality; (3) long movements within the non-breeding season, including irruptions and weather movements; (4) opposite direction migrations, in which some species migrate to higher, rather than lower, latitudes after breeding, but at the same time as other migrants migrate to higher latitudes to breed; and (5) nomadism in which birds move around in various directions and distances, seeking areas where conditions are suitable at the time. These variants can all be related to the particular ecological circumstances faced by the species concerned.