Habitat factors influence bird communities in artificial urban wetlands

Background/Question/Methods In natural wetlands factors such as habitat heterogeneity, hydrology, wetland size, adjacent habitat, and wetland density within the landscape influence bird community composition.  It is unclear to what degree these factors influence community structure in an urban system, especially in artificial wetlands such as stormwater ponds. Stormwater ponds are built during development of an area to sequester runoff, sediment, and pollutants from impervious surfaces and construction sites.  Other factors related to the design and function of these ponds may also contribute to species composition. Here we investigated the influences of within pond characteristics and adjacent landscape composition on bird species richness in stormwater ponds in an urban watershed in Baltimore County, Maryland. We surveyed bird communities in 68 ponds using modified point count surveys three times from May 20 – July 15, 2009. To survey the habitat structure within ponds we recorded percent cover, density and height of vegetation, including shrubs and trees. We measured pond area using a Geographic Information System and used hydrological classifications from the National Wetlands Inventory to quantify hydroperiod.
Results/Conclusions Species richness ranged from 0 to 30 within individual ponds. We found that hydrology, habitat complexity, and habitat size explained 56% of the variation in species richness among stormwater ponds. Most birds observed at the stormwater ponds were birds commonly found in urbanized areas and did not include many species found in natural wetlands of the region. Future analysis will include adjacent landscape structure and geographic distance among wetlands. To date, our results suggest habitat characteristics influence bird species richness within stormwater ponds; however larger scale factors may filter the pool of bird species that could be observed in these urban habitats.