Habitat variables associated with Brown-headed Nuthatch (Sitta pusilla) nesting success in East Texas forests

This study examines how forest structure habitat variables affect nesting success in the Brown-headed Nuthatch in East Texas forests. Previous studies have suggested that Brown-headed Nuthatches have strong breeding habitat preferences that may affect the likelihood of nesting success. A total of 37 nests were observed from 2008--2010 in three forest sites. I compared habitat variables measured at both successful and failed nest sites in an attempt to find variables associated with nesting success. Logistic exposure models indicate a wide range of correctly predicting nest outcome (54--89%). Reduced ability to correctly predict nest outcome in initial models was attributed to inclusion of nests in the relatively unmanaged Stephen F. Austin Experimental forest site. Nest site data were then split into unmanaged habitat (SFA Experimental Forest data) and managed habitat (Boykin Springs and Bannister WMA data) and models were built for each. The most accurate model for predicting nesting success was developed using nests located in the managed habitat and included seven habitat variables. Increased probability of nest success was associated with smaller diameter nesting snags, sites with reduced basal area of pine midstory, and sites with increases in percent bark remaining on the snag, percent herbaceous ground cover, distance from open areas, and number of large and small snags in the habitat. Models developed from nests in unmanaged habitat predicted nest outcomes less than those developed in managed habitat. The results of the model from the managed sites show that management of good quality habitat and conversion of currently unmanaged habitats to conditions described by the managed habitat model may lead to an increase in nesting success in this species.