Compounding effects on nest-site dispersal of Barn Owls Tyto alba

Capsule Recovery distances of Barn Owls ringed as pulli are conditional on ringing date but not on population density. Aims To test whether ring recovery distances (proxy for natal dispersal distances) were conditional on population density and reproductive timing. Methods We used ringing data of pulli ringed in Denmark (1921-2009; n = 590) and GLMMs to test density, recovery time, ringing date and brood size for their influence on dispersal probability and recovery distance. Results The probability of being recovered > 1 km from the nest-site as well as total recovery distances increased steeply from 0 to 100 days after ringing, being stable thereafter, and was also impacted by brood size. Owls ringed very early or late in the breeding season were more likely to be recovered, 1 km from the nest-site at a recovery time where dispersal seemed to be completed. Conclusions Owls from early and late broods showed lower dispersal distances than others on average, despite non-philopatric owls having equal recovery distances regardless of ringing date. Overall, dispersal probability and recovery distances did not correlate with population density, but there is some evidence that young owls dispersed faster in denser populations.