Influences of landscape characteristics on the nesting ecology of female wild turkeys and behavior of raccoons

Abstract

Nest predation is the principle source of reproductive failure in many bird species. Understanding nest predation requires knowledge of interactions between landscape characteristics, and the ecology and behavior of birds and local nest predators. I studied nesting ecology and multi-scale habitat selection of female wild turkeys and the habitat selection and searching behaviors of raccoons, an important nest predator, in a bottomland hardwood forest in Louisiana. My objective was to evaluate the relationships between habitat, wild turkey nest site selection, and raccoon foraging behavior. I used first-passage time (FPT) analysis on nightly foraging tracks of raccoons during the turkey nesting period to test the applicability of the method to a terrestrial predator, determine whether raccoons engage in area-restricted searching (ARS), and to identify areas of concentrated searching activity. Mean turkey home ranges sizes varied from 673ha during pre-incubation to 363ha during brood-rearing. Mature upland forests were selected by turkeys year round. Wild turkeys nested in upland forests (n = 35) and openings (n = 6) offering understory cover, often close to forest edges. Wild turkey reproduction was characterized by low nesting rates (60%) and average nest success rates (39%), and nest predation was the leading cause of nest failure (34%). Mean raccoon home range sizes ranged from 177ha during breeding to 120ha during summer. Seasonal habitat selection varied, presumably as a response to spatio-temporal changes in food availability. Evidence of ARS was found in 55 of 58 paths analyzed and could be induced by supplemental feeding, validating the assumption that ARS represented foraging activity. ARS was associated with lower elevations and shallow standing water, whereas raccoons moved quickly through upland forest habitats with sparse understory vegetation. These results suggest that nest predation by raccoons is incidental rather than the result of targeted searching in habitats with similar structure to those selected by wild turkeys for nesting in this system. This represents the first time FPT has been applied to a terrestrial predator and researchers should consider FPT in future studies of habitat use and foraging ecology of terrestrial predators