Agricultural Land Use and Grassland Habitat in Illinois: Future Shock for Midwestern Birds?

Populations of many common grassland birds in the midwestern United States have been declining in recent decades. These declines have been particularly pronounced in Illinois, where the prairie has been severely fragmented and disturbed by farming. This article describes transitions in agricultural land use in Illinois since the early 1800s, their effects on grassland habitat, and responses by avifauna. Furthermore, factors affecting nesting by birds are considered from a landscape perspective for a study area in central Illinois during the period (1973–1981) when cropping became so intensive that grassland persisted primarily as linear edges. There was a paucity of avifauna nesting on grassy edge habitats on the study area, with a mean of 2.2 nests per ha, representing only eight species. Nest densities and species diversity were highest on study plots where grassland was nearby, where cover types were heterogeneous, and where there were corridors connecting plots to the surrounding landscape. Nest success was variable from year to year, and for Ring-necked Pheasants ( Phasianus colchicus ) the average annual nest success on edge habitats was positively related to the total amount of grassy cover (including hay and small grains) per nesting pleasant. The findings suggest that it is too simplistic to conclude that linear habitats, compared to field settings, are "predator traps." Responses by birds to habitat deteríoration in Illinois may foretell future trends elsewhere in North America where farming practices are becoming more intensive.