Landscape characteristics, spatial extent, and breeding bird diversity in Ohio, USA

Avian communities are often used by ecologists as indicators of environmental decline over large spatial areas, because of the ease with which birds can be monitored by nonprofessionals and the availability of continent-wide breeding bird data. The influence of scale on the relationship between bird diversity and the characteristics of the landscape, which can serve as proxies for decline, is receiving greater attention but is still not well understood. We combined data from the Breeding Bird Survey with landscape characteristics derived from the National Land Classification Data for Ohio, USA, to determine the effects of landscape extent on relationships between birds and landscape characteristics. These relationships were determined through previous work to be correlated with avian richness and diversity. We created areas of varying sizes using buffers around each of 58 routes, and calculated diversity for several groups of birds: all birds, five habitat guilds, and three migration guilds. The landscape extent over which landscape characteristics were considered affected the relationship between these characteristics and bird richness and diversity overall, as well as richness and diversity for several of the habitat and migratory guilds. Diversity of woodland birds, Neotropical migrants, and richness of short-distance migrants were best explained by the landscape characteristics examined here, possibly due to a less homogeneous collection of species in the other guild groups. These results suggest that more attention is required in selecting the appropriate scale when using landscape characteristics to predict or manage avian communities, as some characteristics may be more useful for management activities over small areas versus efforts over larger areas.