Factors Influencing Distribution and Abundance of the Loggerhead Shrike (Lanius ludovicianus migrans) in South-Central Illinois

The loggerhead shrike (Lanius ludovicianus) is listed as a threatened species in Illinois as a result of population declines that have occurred since approximately 1900. Although Graber et al. (1973) reported that this species had been largely extirpated from the northern two-thirds of Illinois by 1965, there has been no research on shrike distribution or abundance in the state since that time. Consequently, a roadside survey was completed in 32 south-central Illinois counties to delineate the abundance of loggerhead shrikes in the study area and attempt to relate their abundance to land-use patterns among counties surveyed. Two hundred and eleven loggerhead shrikes were observed in 22 of the 32 counties and they were most abundant in nine southeastern counties (Clay, Clinton, Hamilton, Jefferson, Lawrence, Marion, Richland, Wayne, and White). Also observed were 32 active nest sites and nest success appeared to be relatively high in the study area. Shrike abundance was positively correlated with the amount of pastureland, hay meadows, and cover crops and negatively correlated with the amount of harvested cropland and woodland in each county. Changing land-use patterns have, and will continue to, influence the distribution and abundance of the loggerhead shrike in Illinois. Other limiting factors, including competition on the wintering grounds and nesting in marginal habitat need to be addressed in the future