2025 Midwest Fish & Wildlife Conference

AUTHORS: Lauren C. Scopel, Illinois Natural History Survey; T.J. Benson, Illinois Natural History Survey; Maximilian L. Allen, Illinois Natural History Survey; Kirk W. Stodola, Illinois Natural History Survey

ABSTRACT: Wildlife face increasing threats from a variety of anthropogenic sources, yet wildlife research, monitoring, and conservation funding is increasingly at risk. Wildlife managers thus face pressure to become more efficient, reducing time available for long-term survey efforts. One potential way to complement existing surveys is the use of publicly available federal or citizen science data. We integrated data from the Illinois Department of Natural Resources (IDNR), the Breeding Bird Survey (BBS), and eBird to analyze the distribution of Northern Bobwhite (Colinus virginianus) and Ring-necked Pheasant (Phasianus colchicus) in Illinois between 2010-2022. We used dynamic occupancy models and Bayesian methods to track long-term changes for each species, while also examining potential bias in sampling design for each survey type. Bobwhite and pheasant occupancy declined over the 13-year period and were negatively associated with urban land cover. Of the three surveys, IDNR had the greatest detection rates for both species, whereas eBird detection rates were lowest, especially for bobwhite. eBird data, unlike the other data sources, also showed a bias in sampling effort, where users preferentially surveyed urban and wetland areas relative to their occurrence in the state. Our results indicate that intensive monitoring should continue for gamebirds in Illinois, given their ongoing declines. BBS and eBird data can complement high-quality IDNR data, but eBird data especially need additional treatment during analysis to ensure more accurate occupancy estimates.