Grassland-obligate birds are undergoing some of the steepest population declines of all North American passerines. Few studies have addressed these species' patterns of habitat use in their winter ranges in the southeastern United States. The dry prairie of south-central Florida constitutes one of the largest areas of contiguous grassland remaining within this region and during winter supports a diverse group of migratory grassland-obligate birds. Modern land-use of this region has altered the ecosystem's natural fire regimes and shifted the vegetative community away from graminoids and forbs toward overabundance of woody-stemmed species such as the saw palmetto (Sereona repens). Simultaneously, the prairie's historic range has decreased with urban development and conversion to agriculture. In order to understand how these changes affect overwintering grassland birds, we documented the dry prairie's winter bird community and evaluated the effects of habitat characteristics and time since fire on the occurrence of the Grasshopper Sparrow (Ammodramus savannarum pratensis) and Sedge Wren (Cistothorus platensis), two winter residents. We surveyed birds via flush transects and used an information-theoretic approach to select models that best predicted the species' occurrence. Time since fire was the best predictor of the Grasshopper Sparrow both years of our study, and occupancy by the Grasshopper Sparrow was six times more likely if transects were burned within the previous year. The Sedge Wren favored longer intervals between fires, and its response to habitat covariates in the two years differed. These results highlight the need for dry prairie to be managed with natural (1–3 years) fire-return intervals to maintain wintering habitat for declining grassland birds.
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Vol. 111 • No. 3