Effects of Urbanization on Avian Community Organization

The avian community of a mature residential area was studied and compared with an undisturbed climax beech-maple forest. Urbanization was presumed to be responsible for decreasing species richness and diversity, increasing biomass and density, and favoring dominance by a few species. Foraging guilds shifted from forest insectivores that were canopy foliage gleaners or bark drillers to urban ground gleaners. Analyses of habitat structure showed that although urban foliage height diversity was like that of the forest, the urban area contained only one-third of the total percent vegetative cover. As compared to the forest, urban vegetative cover was: (1) significantly less in all but the middle layer; (2) replaced by man-made structures, ground cover and ornamental vegetation in the low and middle layers but dominated the high layer; and (3) highly discontinuous, existing as isolated strata. Differences in avian community organization between the forest and urban area are discussed in relation to urban habitat manipulation and population-suppressing factors.