Effects of food provisioning and habitat management on spatial behaviour of Little Owls during the breeding season

摘要

The population of Little Owls in Denmark is close to extinction. The main cause is food limitation during the breeding season. Efforts to improve breeding success include providing breeding pairs with supplementary food and attempts to improve foraging habitats by creating short grass areas near the nests. In addition to increasing the reproductive output, feeding and habitat management may cause parents to work less hard improving their future reproductive value. We studied working efforts of five radio-tagged Little Owl pairs in years of absence and presence of food provisioning, and/or access to short sward vegetation areas near to the nest. We quantified movement as the minimum flight distance hour(-1) (MFD), using the mean distance from the nest (DN) as a supplementary index. Under unmanipulated conditions, males had higher MFD and DN than females. If provided with food and/or areas with short sward vegetation, males but not females reduced their MFD and DN significantly. If MFD was adjusted for DN ( the two measures correlated positively), both sexes reduced their DN-adjusted MFD as response to food provisioning but not to habitat provisioning. Food provisioning therefore had similar proximate effects on the foraging effort of males and females, whereas provisioning of short sward habitats had an indirect effect on male but not female MFD, because of decreased commuting distances between nest and foraging sites. The results indicate that food provisioning not only leads to increased reproductive output in an endangered raptor, but also to decreased working effort, which in turn may improve adult survival.