Modeling species distributions: Indiana's terrestrial vertebrate communities with special emphasis on the Henslow's sparrow

Over the last two centuries, wildlife habitats have disappeared or become heavily fragmented across Indiana. The aim of the Indiana Gap Analysis Project (INGAP) is to evaluate Indiana's present landscape for remaining areas of biological importance. My research as part of the INGAP focused on the development of models that predict the geographic distribution of each of the 290 terrestrial vertebrate species in Indiana. These models are based on known habitat associations for each species and a geographic vegetation classification of Indiana with seventeen distinct habitat types. Models based on the standard methods of gap analysis were generally acceptable, but mainly for species with broad habitat preferences. I therefore developed advanced modeling procedures for 107 species that specialize on habitat edges or habitat adjacent to streams, or occur only in large blocks of habitat. I focused specifically on the advanced model for the Henslow's sparrow, a state-endangered bird, to reveal potential habitat for this species in southwestern Indiana. This model predicted the occurrence of this sparrow in 19 large reclaimed coal mine grasslands, and subsequent field work in these mines documented a large, previously undiscovered population of Henslow's sparrows. A further elaboration of this advanced model showed that both landscape composition and habitat configuration had surprisingly little effect on Henslow's sparrow abundance, suggesting that these large grasslands may exceed the size thresholds for such effects. Reclaimed coal mines clearly serve to promote the conservation of Henslow's sparrows and other grassland birds.