Postfledging Dispersal

Once they become independent of their parents, the young of many bird species disperse from their natal sites, for a time moving in various directions and progressively further with increasing age (Table 17.9). As birds hatched in particular study areas gradually leave, others hatched elsewhere move in. This moving and mixing happens every year at this time regardless of local conditions. Yet post-fledging dispersal is the least conspicuous of all bird movements, for it occurs at a time when many birds are at their most silent and often moulting. They accumulate no special body reserves, and although they appear in a wider range of habitats and places than when nesting, they undergo no large-scale distributional change. Evidently, the tendency to disperse is inherent (and presumably endogenously controlled), but the actual distances that individuals move may be influenced by environmental conditions, as explained above. After a period of post-fledging dispersal, individuals of many sedentary species appear to stay in those areas thereafter, whereas individuals of migratory species depart for their winter quarters.

Table 17.9 Percentage of European Pied Flycatchers Ficedula hypoleuca caught at different distances from the natal site at successive ages

Age of birds (days)

Number caught

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