Habitat use by loggerhead shrikes (Lanius ludovicianus) at Midewin National Tallgrass Prairie, Illinois: An application of Brooks and Temple's habitat suitability index

摘要

Declines in loggerhead shrike populations have been attributed to pesticide use and habitat loss on the breeding grounds and factors outside the breeding range. To determine the role of breeding habitat limitation, Brooks and Temple (1990) designed a habitat suitability index for shrikes based on data from Minnesota. This paper describes an application of their model to a site in Illinois. Like Brooks and Temple, I found that breeding habitat does not appear to limit shrike populations and shrikes seem to be making settlement choices based on discernable habitat criteria. I suggest changes to the model for adaptation to Illinois shrike populations, including an adjustment of the cutoff for "suitable" habitat, an adjustment of the conversions of variables leading to the calculation of the index (V4 to S14), the use of GIS to measure variables (usable foraging habitat) and the addition of variables (length of fence) used in the model.