Distribution and Abundance of Birds in the Loess Hills of Western Iowa

Recent investigations have provided a good understanding of the distribution and abundance of birds in the Loess Hills. Surveys have been conducted during natural history forays sponsored by the State Preserves Advisory Board and by our quantitative investigation during 1982-83. Fifteen stations covering the entire length of Iowa\u27s Loess Hills landform were visited. Three habitats were sampled at each station: native grassland, agricultural (brome or alfalfa) field, and forest. This paper describes typical bird communities of each habitat and compares species composition within and between stations. Grassland bird communities tend to be richer in the northern Loess Hills; the opposite is true for forest bird communities. Cultivated grasslands generally support a greater diversity of species than do native prairies. A notable exception occurs in Plymouth County, where extensive tracts of prairie are inhabited by a relatively diverse assemblage of grassland birds. We propose that small area, steepness of slope, and other factors render today\u27s prairie remnants poorly suited for grassland birds. The best quality grasslands in the Loess Hills probably occurred in lowlands or on gentle slopes, which today have been converted to agriculture. The richest diversities of birds in the Loess Hills occur in forests, a habitat type that was not extensive at the time of settlement