Can Urban Greenways Provide High Quality Avian Habitat?

Abstract

As natural areas are converted to urban or suburban development, landscape and urban planners are pressed to integrate wildlife habitat into a rapidly changing landscape. Urban greenways provide a broad range of social, economic and environmental benefits, and consequently are enjoying worldwide popularity as a developing form of urban openspace protection. One of the goals of greenway development often is to provide habitat for wildlife. If landscape and urban planners are to strategically design greenways so as to maximize their value to wildlife, they need information on the specific environmental characteristics in and surrounding urban greenways that contribute to their value as wildlife habitat.

I investigated how forested corridor width, land use context, and greenway composition and vegetation structure affected avian community composition in urban greenways in Raleigh and Cary, North Carolina, USA. I surveyed breeding bird communities at 34 greenway study sites using 50-m fixed-radius point counts located at the center of 300m long greenway segments. Each greenway segment's forested corridor width and surrounding land use were determined in ArcGIS. Greenway composition (proportion of mature forest, young forest, managed area, and stream in the greenway study site) and vegetation structure were measured in the field.

Total bird abundance increased with increasing canopy cover in the adjacent landscape and increasing shrub cover within the greenway. Neotropical migrant, insectivore and forest-interior species richness decreased with increasing amounts of managed area, such as trail and other mowed or maintained surfaces, within a greenway. Neotropical migrant species richness and forest-interior species richness and abundance decreased with increasing amounts of building in the adjacent landscape. Insectivore species richness increased with increasing lawn cover in the adjacent landscape, and insectivore abundance increased with increasing amounts of canopy in the adjacent landscape. White-eyed Vireos were recorded only in greenways wider than 300m; Wood Thrushes and Indigo Buntings were recorded only in greenways wider than 100m; and Blue-gray Gnatcatchers, Downy Woodpeckers and Red-eyed Vireos were recorded only in greenways wider than 50m. Urban-adaptors such as Common Grackles and European Starlings were more common in narrower greenways.

Landscape and urban planners can maximize native bird diversity and abundance by minimizing the width of the greenway trail and associated mowed and landscaped surfaces adjacent to the trail, maintaining vegetative structure within the greenway, and giving priority to the protection of greenways in areas of lower development intensity. Greenways wider than 50m provide habitat for a diversity of bird species, but many species of conservation concern require much wider greenways.