||Bachmanís Sparrow (Aimophila aestivalis) is a national species of conservation concern because of declining populations and loss of savanna ecosystems. Populations have decreased an average of 1.6 % per year from 1966 to 2007 across the entire range based on analyses from North American Breeding Bird Survey data. Bachmanís Sparrows are traditionally found in pine savannas in their core range along the Gulf and Atlantic coasts, but use oak savannas in the northerly portion of their range, which reaches as far as Illinois and Pennsylvania. Fort Campbell, located on the border of Tennessee and Kentucky, contains the largest known breeding population of Bachmanís Sparrows in oak savanna habitat. The goal of our research at Fort Campbell during 2009-2010 was to document population size, habitat use, and breeding ecology. Forty-three Bachmanís Sparrows were found in patches of frequently burned and disturbed areas, and territories were mapped for 27. Occupied territories had a higher percent cover of forbs (27.67%) than the adjacent available savannas (20.45%), but did not differ in percent cover of native warm-season grasses (28.68%, 27.58%), standing senescent grass (6.79%, 4.56%), woody species (9.48%, 10.47%), sericea lespedeza (5.7%, 2.8%), litter (13.90%, 11.94%), or bare ground (15.11%, 16.62%). Territory size per bird was 2.66 ha +- 0.57and basal area per territory was 2.25 m2/ha +- 0.65. Occupancy of Bachmanís Sparrows on point counts was low during both breeding seasons (ψ=0.1), demonstrating the difficulty of using traditional ground- based monitoring for accurate population estimates. Our long-term goal is to use these data to develop a conservation strategy to both monitor and enhance populations of this high-priority species at Fort Campbell and elsewhere in the region.