Breeding biology and nest survival in Tropical Screech-Owls (Megascops choliba) in the Brazilian Cerrado

Abstract

Different ecological parameters are associated with the selection of nests and breeding sites in birds. Understanding nest-site selection and the subsequent consequences for reproductive success are critical to a full understanding of how natural selection shapes birds’ nesting behavior. Between 2007 and 2008, we evaluated nest-site characteristics and nesting success of Tropical Screech-Owls (Megascops choliba) in an area of Cerrado interspersed with cultivated areas in central Brazil. We compared the characteristics of cavities used for nesting by owls and unused nesting cavities and modeled nest survival in MARK. Models were assessed using Akaike’s Information Criterion for small sample sizes (AICc) and model averaging was used to infer model parameters. Tropical Screech-Owls nested in tree and termite-mound cavities. Nest success was 44.4%, with predation being the main cause of nest failure. We found that Tropical Screech-Owls nested in cavities with different orientations, and closer to the ground than unused cavities. Although the top-ranked models included nest height and nest concealment, multimodel inference showed that these variables had no clear effect on nest survival. Despite the lack of effect of these variables on nest survival, nest-site characteristics commonly associated with a cavity’s microclimate (i.e., orientation of cavity entrance) may still have a stronger influence on nest-site selection.