Consequences of Eagle Owl nest-site habitat preference for breeding performance and territory stability

I tested the hypothesis that nest-site habitat preferences are adaptive in an Eagle Owl (Bubo bubo) population fromCentral Spain. Eagle Owls preferred to settle in areas linked with watercourses and with more irregular topography (physiographic gradient) and cover of dehesas andMediterranean forests (vegetation gradient), whereas they avoided sources of human disturbances (human use gradient). Eagle Owls nesting in preferred positions along the physiographic gradient suffered lower clutch loss, probably due to reduced predation. Pairs settled in preferred habitats produced higher quality fledglings but notmore fledglings.Diet analysis suggested that directional selection on fledgling quality could be partially due to better foraging performance in preferred habitats. Territories located in non-preferred habitats showed lower stability, suggesting an adaptive response to spatial variation in fitness that may be mediated by high rates of adult mortality or of breeding dispersal in non-preferred habitat. Overall, these results suggest that habitat preferences are adaptive in the Eagle Owl study population and conservation policies should be focused on protecting preferred habitats.

J. Ortego, Ornis Fennica 84:78-90. 2007