Rehabilitated and wild barn owls (Tyto alba):: dispersal, life expectancy and mortality in Spain

The patterns of dispersal. survival and mortality were analysed in rehabilitated barn owls (Tyto alba) in Spain, including both wild birds after recovery from injuries and captive-bred/released individuals. Comparing these figures to local wild populations released individuals showed greater mortality due to starvation and lower life expectancy. Dispersal did nor differ greatly although wild birds in their first year dispersed more than released birds; dispersal was lower in owls released with opportunities of returning for Food and shelter (hacking). A massive mortality is recorded after release (about 4 weeks) but after this period surviving owls resembled wild populations in mortality patterns. Owls released following training programmes with live prey showed higher survival values. Owls released during summer months showed better survival than those released in autumn. These findings suggest the importance of Recovery Centres (RC) on owl survival. It is strongly recommended that Spanish RCs should reconsider their methods in order to optimise results and the efficient use of resources. (C) 2000 Elsevier Science Ltd. All rights reserved.