• Glennon, Michale
  Wildlife Conservation Society Adirondack Program
  
• Krester, Heidi
  Wildlife Conservation Society Adirondack Program
  

Our prior research in the Adirondacks has shown that a zone of up to 200m from a residential house is an area in which bird community characteristics, and potentially those of other wildlife, are altered. This results in an “ecological impact zone” of some 31 acres surrounding a single home. In order to determine if the impacts associated with homes were due to houses and their occupants or to adjacent roads, we set out to measure the ecological impact zone of a range of road types in the Adirondack Park. We used birds as indicator taxa so as to compare with the prior study and used a standard count method to sample bird communities at the road edge, and at 200m and 400m into surrounding forest. We sampled along roads placed into 3 levels of hypothesized impact based on width, average speed, and average traffic levels. We analyzed the response of birds both at individual species and family level. We also applied an Index of Biotic Integrity developed previously by Glennon and Porter (2005) in order to examine how roads impacted breeding bird community integrity. For a majority of species, the type of road more strongly shaped the response of birds than did the distance from it. When grouped into families, however, birds responded more strongly to the distance from the edge of the road than to the road type, suggesting that responses to roads are highly species-specific. These responses were of 3 basic types. A number of species were attracted to road edges and in lower numbers farther away from roads. Expectedly, a number of species also responded negatively to road edges. Most interestingly, a third group of birds had high occupancy at road edges and in interior forest (400m), and low occupancy at 200m. It appears that the size of the ecological effect zone may extend as far as 200m for both roads and houses, but the relative impacts of the two are varied. Houses had stronger impacts on all aspects of biological integrity – structural, functional, and compositional – than did roads. Roads may provide foraging and feeding opportunities for a number of species, but less in terms of nesting or primary habitat versus areas near houses. Our results run counter to other studies which suggest that road traffic can have a strong negative impact on breeding bird densities near roads; this is likely because the roads studied here were all smaller and of lower traffic densities than those examined by other researchers, and they are probably similar to many throughout the Northern Forest. It appears that relatively narrow, low-traffic roads in this region do not have a strong negative impact on songbird communities. Information on reproductive success and survivorship of birds breeding near roads in the rural northeast would help to determine whether or not the attraction effect that roads appear to cause for birds is ultimately an ecological trap.