Nest Density, Productivity, and Habitat Selection of Red-Shouldered Hawks in a Contiguous Forest

Abstract

We measured habitat selection, productivity, and nest density of Red-shouldered Hawks (Buteo lineatus) breeding in a largely contiguous forest in northern Wisconsin. We located and followed the reproductive success of 71 breeding attempts within an estimated 26 territories between 2002 and 2006. Mean reproductive rates were 0.7 young per breeding attempt and 2.0 young per successful nest, and nest success averaged 35% per year. Annual nest density ranged from 0.10–0.16 nests per km2. Micro- and macrohabitat variables were measured at 400-m2 circular plots centered on nest trees and at random plots located in similar forest types. When compared to random plots, nesting areas were significantly shorter distances from the nearest lake or treeless wetland (P < 0.001). The logistic regression model that provided the best fit for our data included the distance to nearest trail or road and the distance to nearest lake or treeless wetland. At the microhabitat scale, nesting areas had greater basal areas and fewer sapling-sized trees (i.e., trees 3–13 cm in diameter at breast height) than found at random plots. The low reproductive success in combination with the observed nest density suggests that immigration of Red-shouldered Hawks from outside the study area may be critical to maintaining this breeding population.