Wetlands as habitat in urbanizing landscapes: Patterns of bird abundance and occupancy

Wetlands in urban landscapes provide nesting opportunities for wetland breeding birds as well as enhanced food resources that may be utilized by opportunistic species and those that can tolerate human activity. We investigated the degree to which birds utilize urban wetlands by examining breeding bird communities in urban and rural wetlands and nearby uplands in the northeast US. From mid-May through June in 2008, we conducted 10-min, 50 m radius point counts at 99 randomly chosen sites along a gradient of watershed urbanization. Bird abundance and species richness was significantly higher in wetlands versus uplands, and at urban wetlands versus urban uplands, but not at rural wetlands versus rural uplands. Overall, more species were present at wetland versus upland sites, but the difference between wetland and upland was less for human-tolerant species. While the amount of natural vegetation within a 50 m buffer of a site was significantly negatively correlated with the amount of urban land within 1 km, bird abundance and species richness increased. Species-specific habitat models using general vegetation classes showed differences in bird habitat associations as watersheds became more urbanized. Our findings demonstrate the importance of wetland habitats for birds, and add to the body of evidence that supports the protection and restoration of wetlands as a means towards maintaining or enhancing habitat heterogeneity and biodiversity in urban landscapes.

Research highlights▶ Species-specific habitat models using general vegetation classes showed differences in bird-habitat associations as watersheds became more urbanized. ▶ Birds may be responding to mesic conditions by preferentially using wetland habitats, particularly in urban areas. ▶ Wetlands may also be supporting less ubiquitous or human intolerant birds that are targets for conservation. ▶ Changes in the extent of urbanization may impact bird use of remnant natural habitats to the extent that wetlands may be inordinately beneficial to maintaining populations of some species in human-dominated landscapes.