RESPONSE OF BIRD SPECIES DENSITIES TO HABITAT STRUCTURE AND FIRE HISTORY ALONG A MIDWESTERN OPEN–FOREST GRADIENT

Abstract

Abstract Oak savannas were historically common but are currently rare in the Midwestern United States. We assessed possible associations of bird species with savannas and other threatened habitats in the region by relating fire frequency and vegetation characteristics to seasonal densities of 72 bird species distributed across an open–forest gradient in northwestern Indiana. About one-third of the species did not exhibit statistically significant relationships with any combination of seven vegetation characteristics that included vegetation cover in five vertical strata, dead tree density, and tree height. For 40% of the remaining species, models best predicting species density incorporated tree density. Therefore, management based solely on manipulating tree density may not be an adequate strategy for managing bird populations along this open–forest gradient. Few species exhibited sharp peaks in predicted density under habitat conditions expected in restored savannas, suggesting that few savanna speciali...