PARENT SESSION
Oral Session #29: Spatial Ecology and Disturbance Ecology.
Presiding: J. Ludwig
Tuesday, August 6. 8:00 AM to 11:30 AM. Coconino Meeting Room, TCC.

The spatial impact of urban land cover on avian diversity.

Butler, Russ^*,1, ¹ University of Michigan, Ann Arbor, Michigan

ABSTRACT- The spatial extent to which urban centers impact biodiversity is not well understood. I conducted a breeding-bird distribution study containing over 2,000 roadside survey locations in a 500,000 ha study area in north-central Tennessee, USA, that contained areas of natural and urban (mainly the city of Nashville) land cover. The study area was further subdivided into blocks at four smaller scales: 36 ha, 2,580 ha, 15,480 ha, and 61,920 ha. Breeding bird species were divided into three migration guilds: those that breed and winter in the same area, residents; those that breed and winter in different but relatively close areas, short-distance migrants; and those that breed in North America and winter in Central and South America, Neotropical migrants. The association between species richness of these four bird groups and amount of urban land cover were assessed at the different scales. Survey locations were statistically grouped according to urban land-cover density and avian richness. These data were then spatially analyzed through spatial interpolation surface models. At all scales, Neotropical migrant richness exhibited stronger negative associations with amount of urban land cover, than either residents or short-distance migrants. The surface model for urban land cover formed definite density zones that corresponded to urban land cover pixel density. Surface modeling of resident richness produced only local variations in species numbers. Both short-distance and Neotropical migrant surface models revealed greater zonation in avian richness than the resident species surface model with Neotropical migrants exhibiting strong spatial correspondence with the urban density zones. Zones with low numbers of Neotropical migrants spatially corresponded to high urban density zones. The urban effect of reduced Neotropical diversity was found to extend to an area over 50 times the area, the metropolitan area effect, of downtown Nashville. Assessment of the overall metropolitan spatial effect to diversity will provide a benchmark of areal urban/suburban impacts that will assist conservation and management strategies directed towards controlling environmental impacts of urban sprawl.

KEY WORDS: Urbanization, Sprawl, Spatial, Birds