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Greenways for Wildlife

If urban and landscape planners are to successfully incorporate the needs of wildlife into greenway planning and design, they must have some idea of which characteristics of greenways contribute to their wildlife habitat value.

Greenways for Wildlife seeks to address this need by establishing design guidelines for greenways in the language of landscape and urban planners.

We are developing recommendations on how forest corridor width, adjacent development intensity, and other factors can be managed to attract a variety of wildlife.

In Progress
No work currently in progress (posted 2010 June 4)

Completed Studies
  • Breeding bird habitat
  • Migrant bird stopober habitat
  • Mammalian nest predators
  • Aquatic salamanders
  • Exotic invasive vegetation
  • Publications
    We've provided PDFs of student theses, but we can't provide PDFs of published manuscripts because of copyright restrictions.
    We can provide copies of the published papers on request.
    Breeding Bird Habitat

  • Hull, Jamie R. 2003. Can urban greenways provide high quality avian habitat? MS Thesis, North Carolina State University, Raleigh, NC. (PDF 700Kb)
  • Mason, J.H., C.E. Moorman, G.R. Hess, and K.E. Sinclair. 2007. Designing urban greenways to provide habitat for breeding birds. Landscape and Urban Planning 80: 153-164.

    Migrant Bird Stopover Habitat

  • Kohut, Salina M. 2005. Avian use of suburban greenways as stopover habitat MS Thesis, North Carolina State University, Raleigh, NC. (PDF 950Kb)
  • Kohut, S.M., G.R. Hess, & C.E. Moorman. 2009. Avian use of suburban greenways as stopover habitat. Urban Ecosystems 12(4): 487-502.

    Exotic Invasive Vegetation

  • Vidra, Rebecca l. 2004. Implications of exotic species invasion for restoration of urban riparian forests. PhD Thesis, North Carolina State University, Raleigh, NC. (see Chapter 4)
  • Vidra, R.L. & T.H. Shear. 2008. Thinking Locally for Urban Forest Restoration: A Simple Method Links Exotic Species Invasion to Local Landscape Structure. Restoration Ecology 16(2): 217-220.
  • Mammalian Nest Predators

  • Novotny, Kristen E. 2003. Mammalian nest predator response to greenway width, habitat structure, and landscape context. MS Thesis, North Carolina State University, Raleigh, NC.
  • Sinclair, K.E., G.R. Hess, C.E. Moorman, and J.H. Mason. 2005. Mammalian nest predators respond to greenway width, landscape context, and habitat structure. Landscape and Urban Planning 71(2-4): 277-293.

    Aquatic Salamanders

  • Miller, Jennifer E. 2005. Impervious surface cover: Effects on stream salamander abundance and a new method of classification using feature analyst. MS Thesis, North Carolina State University, Raleigh, NC. (PDF 3.5Mb)
  • Miller, J.E., G.R. Hess, & C.E. Moorman. Southern two-lined salamanders in urbanizing watersheds. Urban Ecosystems 10(1): 73-85.
  • Summary of Findings - Thesis Abstracts
    HULL, JAMIE REBEKAH. 2003. Can urban greenways provide high quality avian habitat?
    (Under the direction of Christopher E. Moorman and George R. Hess.)

    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.

    >> more on breeding bird habitat >>

    KOHUT, SALINA MARVELLE. 2007. Avian Use of Suburban Greenways as Stopover Habitat.
    (Under the direction of George R. Hess and Christopher E. Moorman.)

    The decline of Neotropical migrant songbirds has called attention to the need for habitat conservation along the entire migratory route, and scientists now recognize the need to conserve stopover habitat in addition to habitat on the breeding and wintering grounds. Greenways are a popular means for accomplishing conservation goals in suburban areas and might provide stopover habitat in urbanizing areas where habitat loss and alteration are accelerating.

    My study examined the effects of greenway forested corridor width, greenway vegetative characteristics, and adjacent land cover on the species richness and abundance of migrant songbirds during spring and fall migration. I conducted the study to provide city planners with management recommendations for the construction and maintenance of greenways that will benefit migrating songbirds. During spring and fall migration, 2004, and spring migration, 2005, I surveyed birds in 47 segments of public greenway in Raleigh and Cary, North Carolina, USA representing a range of forested corridor widths and adjacent land covers. I also surveyed three reference sites along trails in William B. Umstead State Park, the largest contiguous forested area (2,201-hectares) nearest the study greenways.

    Migrant species richness was higher in wider greenways in both spring and fall. During spring migration, migrant bird richness and abundance generally increased with tree height and percent hardwood tree composition, and abundance was greater in greenways with more shrub cover. During fall migration, migrants occurred most commonly in greenways with lower canopy cover and higher shrub cover. Although forest-interior migrant richness was not correlated with greenway forest corridor width in either season, they were more abundant in the reference sites than in the greenways during spring and fall. During spring, forest interior migrants were less common in greenways surrounded by more bare earth and pavement cover, both signs of intense development.

    Though migrants used greenways of all widths, forested corridors wider than 150 m had the greatest overall diversity and abundance of migrants. Therefore, planners should conserve the widest greenway corridors possible. Shrub and ground cover should be retained within the greenway to provide the complex vegetative structure that migrants use. In urbanizing areas, planners can provide stopover habitat for forest-interior migrants by constructing greenways in areas of lower development intensity and by conserving larger parks or reserves in addition to greenways.

    >> more on migrant bird stopober habitat >>

    NOVOTNY, KRISTEN ELISE. 2003. Mammalian Nest Predators Respond to Greenway Width, Habitat Structure, and Landscape Context.
    (Under the direction of George R. Hess.)

    Birds of conservation concern breed in suburban greenways, yet abundant populations of mammals that depredate bird nests may compromise nest success. We evaluated how three factors influenced total mammalian nest predator abundance and individual species abundance in greenways of Raleigh and Cary, North Carolina, USA: 1) the width of the forested corridor containing the greenway, 2) the type of land-use adjacent to the forested corridor, and 3) the habitat structure within the greenway. Forest corridor width and adjacent land-use were measured for 34 greenway segments using aerial photographs. Several measures of habitat structure within the greenway were collected in the field during September 2002, including trail width and surface type, stream width, and percentage of mature forest. We measured the relative abundance of mammalian nest predators with scentstation transects, operated for five nights during the 2002 breeding season.

    Mammalian nest predators were significantly more abundant in greenways within narrower forested corridors. Mammalian nest predator abundance was lowest in greenways with forested corridors wider than 200 meters, and continued to decline as forest corridor width increased. Most of the species we identified are known to inhabit edge habitat, which was present throughout greenways within narrow forested corridors. We found no relationship between categorical measures of land-use context (lowdensity residential, high-density residential, office/institutional) and mammalian nest predator abundance. Specific landscape features adjacent to the greenway, however, did affect mammalian nest predator abundance. Greenways adjacent to landscapes with fewer buildings had a higher abundance of total mammalian nest predators, and the abundance of individual species varied with the amount of canopy, lawn, and pavement in the adjacent landscape.

    The habitat structure of the greenway was correlated with the mammalian nest predator community, yet no habitat structure variables were significant in all species models. Segments with wider trails had a higher abundance of mammalian nest predators, as did sampling areas located closer to trails and with more mature forest. Raccoon abundance was higher in segments with wider trails, and lower in segments near parking lots or roads, playing fields, and backyards. Opossum abundance was higher in segments near water and trails. Gray squirrel abundance was higher in segments near backyards. Domestic cat abundance was higher in segments with more mature forest, near parking lots or roads, and lower further from streams.

    To reduce the risk of avian nest predation by mammals, greenways should be designed with wider forest corridors and narrower trails, particularly natural dirt footpaths instead of paved or cleared trails. Additional features of greenways are likely to increase the abundance of particular species. Greenway forest corridors with more paved areas in the adjacent landscape are likely to have higher abundances of rats and mice, and domestic cats if the paved area borders the greenway. Increasing lawn in the adjacent landscape is likely to increase opossum abundance in greenways. Greenways that border backyards are likely to have a higher abundance of gray squirrels. Increasing canopy cover in the adjacent landscape will positively influence raccoon abundance, as will increasing mature forest within the greenway habitat for total mammalian nest predators and domestic cats. Many of these vegetative characteristics also create habitat for birds of conservation concern. Management of these features must balance reduction of predator communities with promotion of desired bird communities.

    >> more on mammalian nest predators >>

    MILLER, JENNIFER ELIZABETH. 2005. Impervious Surface Cover: Effects on Stream Salamander Abundance and A New Method of Classification Using Feature Analyst.
    (Under the direction of George R. Hess.)

    Increasing impervious surface cover associated with urbanization degrades water quality and alters wildlife habitat. Forested riparian buffers are one popular method of mitigating the effects of impervious surface cover. My study was designed to investigate the effects of impervious surface cover and forested riparian buffer width on the abundance of larval southern two-lined salamanders (Eurycea cirrigera). I sampled 50-meter reaches of 43 streams, representing the range of impervious surface cover and forested riparian buffer width combinations across Wake County, North Carolina, USA in 2004. Additionally, I measured physical and chemical stream properties to account for local habitat effects.

    Percent impervious surface cover in the catchment, percent detritus cover in the stream, percent pebble substrate in the stream, and average water conductivity were significant predictors of larval E. cirrigera abundance. Forested riparian buffer width was not a significant predictor. Larval E. cirrigera abundance was lower than anticipated in several streams that appeared to provide good habitat. I discovered that salamander abundance was low in intermittent streams with substrate that is highly sedimented below the surface layer. I suspect that intermittency combined with filled substrate interstices reduced the ability of salamanders to migrate with the water column during dry periods, resulting in low abundances. My research is consistent with a growing body of literature documenting the negative effects of impervious surface on stream biota. In my study, low flow events significantly affected larval E. cirrigera abundance. My findings also suggest that salamander abundance cannot be predicted by measuring the forested buffer width only at the sampling location. A catchment-wide quantification of the stream buffer system, accounting for culverts and other breaches, might yield a better predictive model.

    (Omitted paragraph on feature analyst.)

    >> more on aquatic salamanders >>

    VIDRA, REBECCA LYNN. 2004. Implications of exotic species invasion for restoration of urban riparian forests.
    (Under the direction of Dr. Theodore H. Shear.)

    Chapter 4 abstract: Protection of riparian buffers is becoming increasingly common in urban areas to provide flood protection, sediment filtration, wildlife habitat, and recreational opportunities. Unfortunately, these long, linear strips of forest are susceptible to invasion by exotic species, which can compromise both the native species composition and ecological functions of these buffers. We investigated the influence of landscape structure on buffer invasion in central North Carolina, USA. We assessed the effect of buffer width and landscape context on the exotic species richness, individual species cover, and total exotic species cover in 23 riparian buffers distributed across a rapidly urbanizing region. We characterized landscape context as the proportion of the adjacent landscape that fell into two land cover types: building cover and canopy cover. The most significant predictor variable of exotic species invasion is the amount of canopy cover in the adjacent landscape. Increasing canopy cover is positively correlated to both exotic cover and species richness. Building cover is positively correlated to percentage cover of ornamental exotics but not to total species richness. While the relationship between buffer width and cover and richness of exotic species is negative, this relationship is only significant for buffers narrower than 150m. These results suggest that buffer width, while important, is not the only important factor in determining susceptibility to invasion. The adjacent landscape context significantly influences the extent of invasion, likely by serving as both a source of exotic propagules and by providing external disturbances. We suggest that managers and others interested in conserving native riparian buffer communities focus on the landscape structure of the site to prevent future invasion by exotic plant species.

    >> more on exotic invasive vegetation >>