Conserving a charismatic grassland species in Illinois: the barn owl

As a result of the precipitous loss of grasslands and savannas that the Midwestern U.S. has experienced, populations of many species native to this habitat have declined. One such species is the barn owl, Tyto alba, which is threatened or endangered in 5 states. The conversion of grasslands into agricultural or developed areas has cost barn owls both suitable foraging habitat and nest sites. To mitigate this loss and support barn owl populations, many states, including Illinois, have installed nest boxes in or near grassland habitat. Many of these boxes were never monitored to document their success. Adding to the uncertainty of the barn owl population in Illinois is their secretive, nocturnal nature. Since owls that nest outside of nest boxes are rarely discovered, an effective large scale survey method is needed. My goals for this project were to describe barn owl use of nest boxes, learn how they selected their nest sites, determine factors correlated with nest survival, and test playback surveys as a method of detection. To this end, I checked all known nest boxes in Illinois and monitored active nests until they fledged or failed. I then compared land cover at occupied and unoccupied nest boxes. To determine a response rate for barn owls to broadcasted calls, I conducted nighttime playback surveys close to active nests. I found that barn owl occupancy of nest boxes was positively related to percent cover of grassland and negatively related to percent cover of corn and soybeans with 2 km. Daily survival rate was also positively related to grass cover. Barn owls responded to active playback surveys at a rate of 48.8%, irrespective of time of night, date, or age of the nest. This information is intended to assist biologists in the process of monitoring, managing, and evaluating the status of barn owls in Illinois, with the ultimate goal being the recovery and delisting of the species