Brown-headed Nuthatch occupancy in central Florida and its relationship to forest type, forest structure, and the presence of Red-cockaded Woodpeckers

Abstract

The Brown-headed Nuthatch (Sitta pusilla) is listed as a species of conservation concern throughout most of its range. Forest conditions that support the imperiled Red-cockaded Woodpecker (Picoides borealis) are thought to provide excellent habitat for the nuthatch, but ambiguity exists because the nuthatch has disappeared from some areas where the woodpecker persists. We studied Brown-headed Nuthatches in two forest types that spanned an environmental gradient in central Florida and also differed in terms of forest structure and the presence of woodpeckers. Sandhill forests had mature timber that supported a large woodpecker population (∼70 territories); flatwood forests were dominated by younger pines and supported no Red-cockaded Woodpeckers. We used repeated surveys incorporating broadcast vocalizations and patch-occupancy analysis to assess variation in nuthatch occupancy and detection in relation to forest type, four structural covariates (snag density, basal area of pines and hardwoods, and pine diameter), and proximity to Red-cockaded Woodpecker territories. In our best model, occupancy and detection varied in relation to forest type and pine basal area. Occupancy and detection probabilities were higher in the younger flatwood forests and averaged 0.96 and 0.75 as compared to 0.56 and 0.37, respectively, in older sandhill forests. Occupancy and detection were not influenced by proximity to Red-cockaded Woodpecker territories. The higher encounter rates recorded in younger flatwood forests likely stemmed from differences in habitat quality, while variation attributable to forest structure and woodpecker distribution warrants further study. © The Cooper Ornithological Society 2012.