Post-release survival of unnecessarily captive reared owlets

Nowadays human activity is a major threat to wildlife. Birds of prey are particularly affected due to their location at the top of trophic pyramids and to their low numbers. Ethical and ecological considerations have led to the development of programmes to treat birds with injuries at Rehabilitation Centres (RC) and their later release back into the wild. This paper deals with a crucial aspect of that programme: the survival success of birds of prey after such release. In recent years an increasing number of orphaned but uninjured Strigiform fledglings entered the RC near Parma. Most of these are collected by people from the base of trees because they have fallen either from the nest or when learning to fly. The fledglings are generally attended by parents but people believe they are injured or abandoned and need help to survive from predators. Such human behaviour is a consequence of the Italian people's increasing concern for animal species. As a result, a large number of young owlets are unnecessarily captive reared and this is potentially affecting negatively their post-release survival in the wild. In a first study a sample of 7 young long-eared owls (Asio otus) was studied after release. The owlets remained very close to the release site (less than 1700 m) and did not avoid human settlements. They increased their distance from the release site, but their survival rate was very low; in fact, 3 birds died within a few days. A second study analyzed a sample of young tawny-owls (Strix aluco) released in a woody area. In contrast to long-eared owlets they were more reluctant to move away from the release site, had smaller home ranges, and their survival rate was higher. The results show how rehabilitation of birds of prey is very important to aid recovery from injures, but is almost useless if not accomplished by good monitoring and surveillance of individuals after release into the wild.