Patch and Landscape Configuration Effects on Avian Species Richness in Restored Shrublands

Agricultural intensification has had large negative effects on biodiversity worldwide. In the US population declines of many early successional bird species have been linked with habitat loss due to agriculture. Private land restoration programs, such as the Conservation Reserve Enhancement Program, which convert agricultural land into early successional habitat, have been important to many populations of declining birds in landscapes dominated by agriculture. However, these habitats are often small, isolated, and embedded within highly fragmented landscapes which can negatively influence species richness. In order to understand how these programs can maximize bird conservation on private land restored habitats we evaluated how patch characteristics, habitat amount, and configuration affect the maximum number of bird species within each patch. We calculated species richness from point count surveys for birds in 102 randomly selected restored shrubland patches (x ̅ = 11.4 ha, range = 3–122 ha) in 10 counties in Western Illinois from 2012-2015. We measured patch characteristics as patch size and age. We quantified the landscape composition as the proportion of crop, grassland, development, and forest within buffers at two scales, 200 m and 1200 m using ArcGIS 10.1. Surprisingly, patch size was not a good predictor of species richness. Our top models indicated a positive relationship between species richness and the amount of grass within a 1200 m radius and a negative relationship between species richness and patch age. Our results suggest that private land restored shrubland habitats should be managed at 5-10 year intervals to maintain species richness and species richness will be higher in patches in landscapes with greater amounts of grassland habitat.