Distribution of migratory land birds among forest patches in southern Illinois during spring stopover

Populations of migratory land birds (MLBs) are thought to be in widespread decline. Recently, awareness of habitats used along migration paths, termed “stopover”, and their importance in the persistence of MLBs has increased. Few landscape-scale studies of stopover habitat have been conducted. Accordingly, this research examines forest fragments used as stopover within qualitatively different landscapes. The problem is to determine whether distributions of migrants using forest patches within “habitat-poor” landscapes are similar to those in “habitat-rich” landscapes.; This research identifies landscapes of differing habitat configuration, identifies spatial attributes of 38 randomly chosen sample patches using a Geographic Information System (GIS), observes MLBs within sample patches, and tests hypotheses of bird distributions with these data. Observation of birds within patches was conducted according to standard protocols for timed, unlimited-distance circular-plot point counts. The study area centers on Jackson, Union, and Williamson counties in southwestern Illinois.; Results indicate that landscapes are the primary influence on bird distribution among patches. Qualitative differences between landscapes exist, wherein highest MLB richness and density occur among patches in landscapes of approximately 50% forest cover. Additionally, 5km and 10km scales of observation are ecologically relevant to MLBs. Larger patches were found to contain the greatest richness and density of migratory landbirds regardless of their landscape context. However, small patches have greater density of individuals per unit area. Larger patches harbor a greater number of species than their smaller counterparts, but large patches add increasingly fewer species and fewer individuals as size increases. Small patches therefore “pack” individuals, offering a greater “per unit” benefit than large patches.; Patch isolation and landscape context are found to be significant influences on MLB richness and density among forest patches. Below a “moderate” amount of total forest cover within a landscape (40%), MLB richness and density increase as the amount of forest cover in the surrounding landscape increases. Above this amount of forest cover within a landscape, MLB richness and density decrease within increased forest cover. This suggests that migrating birds detect/select landscapes of total forest cover, and evenly disperse themselves among patches within otherwise habitat-rich landscapes.