Competitors and predators alter settlement patterns and reproductive success of an intraguild prey

The spatial distribution of predators is affected by intra- and interspecific interactions within the predator guild. Studying these interactions under fluctuating food availability, while taking habitat characteristics into account, offers a quasi-experimental set up to determine the relative impact of con- and heterospecifics on reproductive success of predators. We analyzed the settlement decisions and reproductive success of Eurasian pygmy owls (Glaucidium passerinum) in the presence of both breeding conspecifics and their competitor and intraguild predator, Tengmalm's owls (Aegolius funereus), under fluctuating abundance of their primary prey (voles). We used detailed data, collected across 11 years in a large study area (1300 km²), on the spatial and temporal variation of habitat characteristics in all available nesting sites, local densities of both species, and vole abundance. We found that pygmy owls strongly avoided breeding close to conspecifics but did not avoid Tengmalm's o...