Breeding Bird Response to Midstory Hardwood Reduction in Florida Sandhill Longleaf Pine Forests

Abstract

The dramatic loss and degradation of longleaf pine (Pinus palustris) forests in the southeastern United States have contributed to the declines of several bird species associated with this ecosystem. We examined breeding bird response to habitat restoration in longleaf pine sandhill forests of northwest Florida, USA. We compared habitat variables and abundance of breeding birds among 3 hardwood reduction techniques (prescribed spring burning, herbicide application, mechanical felling-girdling) and maintenance of fire exclusion (control). We also examined abundance of breeding birds in fire-maintained, non-experimental reference sites as a means to gauge management success based on similarity analysis. All 3 hardwood reduction methods decreased midstory hardwoods and canopy cover, and increased herbaceous cover compared with fire-suppressed control plots, but had little effect on longleaf pine basal area. Midstory hardwood reduction methods increased the similarity of the breeding bird species assemblages to those found in the reference plots, compared with the fire-excluded control plots. Species that most strongly contributed to the similarity between the hardwood reduction and the reference plots were, in decreasing order of importance: red-cockaded woodpecker (Picoides borealis), red-headed woodpecker (Melanerpes erythrocephalus), tufted titmouse (Baeolophus bicolor), and brown-headed nuthatch (Sitta pusilla). Depending on the similarity index used, additional but weaker contributors to the similarity between the hardwood reduction and the reference plots were northern cardinal (Cardinalis cardinalis), Bachman's sparrow (Aimophila aestivalis), and Carolina chickadee (Poecile carolinensis). Species associated with hardwoods (e.g., tufted titmouse, northern cardinal, Carolina chickadee) contributed to greater similarity of the reference condition by decreasing in abundance after hardwood reduction, whereas open-habitat species increased in numbers, compared with birds on the fire-excluded control plots. Only the detection rates of cardinals and Carolina chickadees were not different among hardwood reduction methods. Two notable species of concern that increased in all hardwood reduction plots compared with the control, but were not strong contributors of the similarity to the reference condition, were northern bobwhite (Colinus virginianus) and southeastern American kestrel (Falco sparverius paulus). Our results suggest that these management methods were beneficial to landbirds characteristic of fire-maintained longleaf pine sandhills in northwest Florida. However, northern bobwhites and Bachman's sparrows may require more intensive management than red-cockaded woodpeckers, such as shorter burn intervals, as these species depend directly on ground cover vegetation. We recommend prescribed spring burning as the most economical and ecologically desirable method for managing breeding bird habitat in longleaf pine sandhill forests.