Abstract

North American grassland birds show long-term population declines that generally exceed the declines of other bird groups. Efforts to conserve grassland birds require knowledge of ecological and habitat requirements during both the breeding and nonbreeding periods of annual life cycles. Nonbreeding habitat associations may affect survival and the acquisition of resources needed for migration and breeding. We focused on the winter habitat associations of a suite of co-occurring grassland sparrows in the dry prairie of south-central Florida, an understudied region within the wintering range of Grasshopper Sparrows (Ammodramus savannarum pratensis) and Henslow's Sparrows (A. henslowii). During the nonbreeding winter months, these two migratory sparrows commingle with resident Bachman's Sparrows (Peucaea aestivalis) and federally endangered Florida Grasshopper Sparrows (Ammodramus savannarum floridanus). We investigated sparrow habitat associations within two defined plant communities of the dry prairie ecosystem, the dry-mesic and wet-mesic prairie, for four prescribed fire treatments over two consecutive winters. Grasshopper and Henslow's sparrows showed higher relative abundance in wet-mesic prairie and Bachman's Sparrows were more abundant in dry-mesic prairie across all fire treatments. Florida Grasshopper Sparrows were detected only in the first and second years post-burn; samples were too small to yield information on potential preferences between the two prairie communities evaluated. We used an information-theoretic approach to select models that best predicted abundances for each species (except Florida Grasshopper Sparrows) based on time since fire and plant community. Abundances of Grasshopper and Bachman's sparrows were best predicted by plant community association and secondly by time since fire; whereas for Henslow's Sparrows, habitat and time since fire were equally important. This is the first concurrent study of these four sparrow taxa in peninsular Florida and indicates that time since fire influences the habitat preferences exhibited by wintering sparrows, but that this role differs across co-occurring species and dry prairie plant communities.

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