The Breeding Ecology of, and Effects of Military Activity on, the Henslow's Sparrow at Fort Drum

Abstract

The Henslow's Sparrow (Ammodramus henslowii) lives in one of the fastest declining habitats in North America, the tall grass prairie. Concurrently, the Henslow's Sparrow population nationwide declined over 91% between 1966-1993. Conservation of Henslow's Sparrows requires in-depth research into the species' breeding ecology, habitat selection, and how humans impact the species. Between 1998 and 2000, I studied Henslow's Sparrow breeding ecology at Fort Drum, New York, an active army base supporting 10,000 troops and part of the largest Henslow's Sparrow breeding population in the Northeast. I studied the abundance and distribution of the Henslow's Sparrow, along with the Grasshopper Sparrow and Savannah Sparrow, using 48, 100-m radius point count plots. All three species' populations fluctuated annually between 1995-2000, based on data collected during my study coupled with data from the Environmental Division of Fort Drum Grassland Bird Study (1995-1998). The Savannah Sparrow population within 2,340 ha western grassland at Fort Drum was estimated at over 250 pairs while Grasshopper Sparrow numbers were minimal at less than 10 pairs. The point count data, however, underestimated Henslow's Sparrows' numbers when compared to banding data; based on banding data and field observations, I estimated the Henslow's Sparrow population in my study area to be 30-40 pairs.