STATUS AND HABITAT SELECTION OF THE HENSLOW SPARROW IN ILLINOIS

Henslow's Sparrows (Ammodramus henslowii), formerly abundant thourgh-o ut Illinois, now are rare and local in occurrence there. Analyse of di stribution and abundance patterns within a representative sample of gr assland fragments showed that habitat area is the most important facto r influencing Henslow's Sparrows in Illinois. Henslow's Sparrows rarel y were encountered on grassland fragments less than 100 ha. However, i n large fragments habitat structure also significantly influenced dist ribution and abundance patterns. Henslow's Spar-rows preferred areas h aving tall, dense vegetation with a high proportion of residual standi ng dead plant material. Prescribed burning and mowing removed the tall , dense vegetation this species prefers and significantly reduced bird densities within parts of grasslands that had been recently managed.