Impacts of urbanizing landscapes on avian diversity in the Mid-Atlantic Coastal Plain: The role of avian dietary guild

Many migratory bird species are declining in abundance. Habitat loss and fragmentation due to urban development is considered a main cause of these declines, and diversity of bird species generally declines with urban development. However, not all bird species respond similarly. Our research explores how bird species respond differently to urban development, depending on their food resources. We studied the relationship between bird diversity and urban sprawl using spatial analyses of the U.S. Geological Survey’s Breeding Bird Survey (BBS) and National Land Cover Data (NLCD) datasets and U.S. Census population data for the Mid-Atlantic Coastal Plain.  Environmental parameters representing landscape composition, landscape structure, and human population density were measured within 300 meter and 1000 meter buffers for each site.  We applied a hierarchical spatial model and Markov chain Monte Carlo methods to identify the explanatory landscape variables related to breeding bird diversity, according to dietary groups.  Our initial findings indicate that breeding diversity responded differently to urbanization parameters according to the birds’ food resources. Insect-eating birds demonstrated the most negative response to urban development, while birds with flexible diets demonstrated the most positive response. These results suggest that food resources are changing with urbanization, with naturally occurring food resources becoming limiting resources for some bird populations, and anthropogenic food resources augmenting others.  In order to understand how continued urban development will affect bird populations and related conservation efforts, future research must examine urbanization impacts in terms of food webs and community interactions.