Effects of Conservation Practice and Site Age on Vegetation Structure and Avian Habitat Use in Fields Enrolled in the Conservation Reserve Enhancement Program

Farmland set aside programs provide important habitat for many wildlife species, yet little information exists regarding how vegetation structure and species respond to conservation practice and site age. This information could provide managers with a guide for how to implement, enhance, and maintain wildlife benefits of these programs. Here, we describe how avian species respond to conservation practice and time since restoration at 172 sites enrolled in the Conservation Reserve Enhancement Program (CREP) in Illinois. To do this we surveyed sites enrolled in four different conservation practices (CPs) within CREP during the breeding seasons of 2012 – 2015 using point counts and vegetation surveys. Vegetation structure and composition varied among CPs with hardwood tree plantings having the greatest amount of understory vegetation, tree and shrub cover, and lowest distance to nearest tree. Conversely, permanent wildlife habitat had the greatest distance to nearest tree, grass cover, and least tree cover. Cover of tree and live vegetation increased and distance to nearest tree decreased with site age and there were conspicuous differences among CPs and site age for these variables and bare ground cover. Avian densities varied among CP types, however only Dickcisselswere significantly greater in sites enrolled as permanent wildlife habitat and, similarly, Bell’s Vireo and Field Sparrow were greater in hardwood tree plantings. Dickcissel density decreased and Field Sparrow density increased as fields aged, but these relationships were not consistent among CP types. Differences among CPs largely resulted from differences in dominance in woody vegetation due to differing management goals. Interestingly, many of our focal species had wider successional tolerances than previously suggested. Our results demonstrate that conservation benefits change over time depending on the starting CP and this information can be used to predict temporal changes in habitat suitability and target conservation benefits toward conservation priority species.