Life path analysis: scaling indicates priming effects of social and habitat factors on dispersal distances

1. Movements of many animals along a life-path can be separated into repeti tive ones within home ranges and transitions between home ranges. We sought relationships of social and environmental factors with initiation and dist ance of transition movements in 114 buzzards Buteo buteo that were marked a s nestlings with long-life radio tags. 2, Ex-natal dispersal movements of 51 buzzards in autumn were longer than f or 30 later in their first: year and than 35 extra-natal movements between home ranges after leaving nest areas. In the second and third springs, dist ances moved from winter focal points by birds that paired were the same or less than for unpaired birds. No postnuptial movement exceeded 2 km. 3, Initiation of early ex-natal dispersal was enhanced by presence of many sibs, but also by lack of worm-rich loam soils. Distances travelled were gr eatest for birds from small broods and with relatively little short grass-f eeding habitat near the nest. Later movements were generally enhanced by th e absence of loam soils and short grassland, especially with abundance of o ther buzzards and probable poor feeding habitats (heathland, long grass). 4. Buzzards tended to persist in their first autumn where arable land was a bundant, but subsequently showed a strong tendency to move from this habita t. 5. Factors that acted most strongly in 1/2-km buffers round nests, or round subsequent focal points, usually promoted movement compared with factors a cting at a larger scale. Strong relationships between movement distances an d environmental characteristics in 1/2-km buffers, especially during early ex-natal dispersal, suggested that buzzards became primed by these factors to travel far. 6. Movements were also farthest for buzzards that had already moved far fro m their natal nests, perhaps reflecting genetic predisposition, long-term p riming or poor habitat beyond the study area.