Social interactions between two owl species sometimes associated with intraguild predation

摘要

Species may act simultaneously as competitor and predator for other species at the same trophic level. This is known as Intraguild Predation (IGP). Most research on this topic describes the final steps of this phenomenon, when one species suffers lost progeny or decreased numbers due to predation and competition by another species. However, little is known about the mechanism that regulates this interaction in previous steps. In this work two species of the same guild (Little Owl Athene noctua and Barn Owl Tyto alba) were selected to test the hypothesis that the hunting and social behaviour of the Little Owl would be conditioned by the presence of Barn Owls. Nine Little Owls were radio-tracked and monitored for nine months. 1223 fixes were obtained and 250 hours of listening were recorded. Moreover, during this time Barn Owls were detected 66 times screeching, hunting or flying in the same areas as the monitored Little Owls. The subsequent activity (movements and voices) of tagged and untagged Little Owls was observed during 30-minute periods. The results show that Little Owl behaviour was affected by Barn Owl presence. When Little Owls noted the presence of Barn Owls, they stayed quiet and silent, or alternatively, sought refuge in the branches of trees or in secure holes in buildings, resuming their activities minutes later, when the risk of predation was presumably lower. This behaviour may have enabled survival and successful breeding of Little Owl in close proximity to Barn Owls.