WINTER ABUNDANCE OF AND HABITAT USE BY HENSLOW'S SPARROWS IN LOUISIANA

摘要

Population trend data indicates the Henslow's Sparrow (Ammodramus henslowii) is declining. Little information is available on the status, distribution, and habitat requirements of this species during winter. We obtained winter density estimates of Henslow's Sparrows and quantified and compared habitat structure along transects occupied and unoccupied by birds in longleaf pine (Pinus palustris) forests in westcentral Louisiana. We flushed Henslow's Sparrows from 14 transects during four surveys of 48 20- X 100-m transects from January to February 1996, and 20 transects during four surveys of 46 of the same transects from December 1996 to February 1997. The range of Henslow's Sparrow densities for both survey periods combined was 0.0―13.8 birds/ha (median = 0.0, 75th percentile = 1.3, 95th percentile = 5.0). We used logistic regression to evaluate the association of vegetative structure with Henslow's Sparrow habitat use. The most parsimonious model included litter depth and herbaceous cover as habitat variables predictive of Henslow's Sparrow occurrence. The model correctly classified the occupancy status of 79% (52 of 66) of observed transects. The number of Henslow's Sparrows observed in transect surveys declined with increased number of growing seasons since the last burn, suggesting fire may influence habitat quality.