Intrinsic And Extrinsic Factors Predict Local Recruitment And Natal Dispersal Distance In A Resident Passerine, The Eastern Bluebird (Sialia sialis)

Natal recruitment and dispersal distances can have important impacts on population dynamics and are influenced by ecological and individual factors. I assessed the intrinsic and extrinsic determinants of local recruitment and natal dispersal from a 3-year study of the breeding ecology of eastern bluebirds (Sialia sialis) in the mountains of North Carolina. Predictors included: offspring sex and body condition, year and seasonality of nesting, and estimates of habitat quality and nest site availability. Offspring were more likely to recruit and dispersed shorter distances when there was greater availability of nestboxes near their natal area. Further, bluebirds that weighed less for their skeletal size were more likely to recruit after fledging from territories with lower percentage of open pasture and grasslands and closer to forest edges, which may be explained by predation pressure following fledging. Alternatively, heavier bluebirds were more likely to recruit when fledged from more open territories but tended to disperse further; this may be explained by competition for nesting sites rather than predation pressure. Overall, dispersal in this species is influenced jointly by intrinsic and extrinsic factors suggesting that the interaction of individual quality, predation, and competition likely shapes natal philopatry in resident passerines.