NEST-SITE CHARACTERISTICS OF BACHMAN'S SPARROWS AND THEIR RELATIONSHIP TO PLANT SUCCESSION FOLLOWING PRESCRIBED BURNS

摘要

Prescribed fire is a frequently applied land-management tool for the preservation and maintenance of southern pine woodlands. Many avian species benefit from the use of prescribed fire in pine woodlands; however, the effect fire has on nesting site characteristics is not well understood for many disturbance-dependent species. We located nests of Bachman's Sparrows (Peucaea aestivalis) in mature longleaf pine (Pinus palustris) forests managed using frequent prescribed fires (return intervals ≤2 years). Vegetation characteristics were measured at each nest (n ＝ 37), within a 0.04-ha area immediately adjacent to nests, and at different time intervals following burns within a larger 20-ha area surrounding nests. We examined vegetation characteristics within the 20-ha area 2, 6, 12, and 18 months after prescribed burns to compare post-fire plant succession with site characteristics associated with nest sites. Nest sites had lower amounts of grass standing crop, grass ground cover, and higher amounts of woody vegetation than found in the 0.04-ha area immediately surrounding nests. Vegetation structure at nests sites was similar to the structure measured across the 20-ha area <6 months following burns, but vegetation structure at ground level began to deviate ≥6 months after fires such that ≥50% of the values differed from the values recorded at nest sites. Results point to the importance of open vegetation structure at ground level and the need for frequent burning to maintain appropriate nesting habitat. Vegetation characteristics associated with nest sites appear to be highly ephemeral and tightly linked to conditions at ground level. As such, suitable nest sites likely represent a subset of areas occupied by singing males.