Abstract
The long‐eared owl is a nocturnal predator which winters communally and breeds in the same areas in loose colonies during the spring. We tested the hypothesis that roosts, particularly stable roosts, are formed by close relatives, a condition under which group‐related behaviours such as information sharing or helping at nest are more likely to be developed. DNA fingerprinting analysis was used to examine genetic similarity within and between two long‐eared owl populations, one wintering in a traditional roost and the other in an unstable roost, and both breeding around their roosting sites. Although genetic similarity within roosts was higher than that between roosts, the difference was not significant. Observed genetic similarity within roosts was smaller than that reported in the bird species whose roosts work as information centres. On the other hand, the presence of some closely related individuals in the roost and behavioural observations suggest that co‐operation between kin might have occurred, at least in one of the two study sites.