PARENT SESSION
Poster Session # 6: Urban Ecology.

Monday, August 4 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Distribution of bird diversity across a gradient of urbanization: The West Georgia project.

Stratford, Jeffrey¹, Robinson, W. Douglas^{1, 2}, Chaney, Philip¹, ¹ Center for Forest Sustainability, Auburn, AL² Oregon State University, Corvallis, OR

ABSTRACT- Spread of human cities into rural areas modifies the distribution and abundance of major vegetation groups. This shift in habitat availability modifies the landscape-level characteristics of avian communities. We investigated how bird diversity varied along a gradient from an urban center, Columbus, Georgia, north into rural areas of the piedmont physiographic region. Breeding bird survey-style point counts (n=550) were used to enumerate species richness and diversity. We used landsat imagery to characterize major habitat configurations at each point and evaluated how habitat and bird diversity changed across the gradient. Three species of conservation concern have been nearly eliminated, occurring only in small remnant populations far from urban areas. Neotropical migratory bird richness changed as a complex function of multiple variables, but was most influenced by total forest cover (positive effect) and amount of edge (negative effect) within 200 m of census points. Urban and suburbanizing landscapes were dominated by a few, widely distributed species and by three non-native species. Although bird species richness is strongly influenced by habitat changes as a function of urbanization processes, total richness and diversity in this landscape is only 65% of predicted pre-European settlement values. Large-scale landscape modification has already taken place, leading to a drop in regional bird diversity. A subsequent major decline occurs when landscapes become urbanized. Without major changes in how urban landscapes are designed avian species richness will be reduced by more than 40%, largely through the local extinction of habitat specialists such as many Neotropical migrant species.

Key words: bird diversity, Neotropical migrants, urbanization, vegetation change