Patterns of Alpha-Diversity and Abundance in Breeding Bird Communities across North America

Abstract

Community diversity can be examined by noting the number of species within a single habitat of known area (alpha-diversity), the changes in species composition along a series of habitats (beta-diversity), or the total species richness of a large geographic region (gamma-diversity; Whittaker 1960, 1972). The diversity of breeding birds in a community is closely related to the structure of the vegetation (MacArthur and MacArthur 1961, MacArthur et al. 1962, 1966, Tramer 1969, Karr and Roth 1971, Peterson 1975, Roth 1976). Studies of beta-diversity in birds have focused on species composition or rates of species turnover between adjacent habitats (Cody 1970, 1975, Tramer 1974a, Karr 1976). Gamma-diversity patterns have been examined for breeding birds (MacArthur and Wilson 1967, Cook 1969, Bock and Lepthien 1975) and wintering birds (Bock and Lepthien 1974, 1976, Tramer 1974a, b) but these studies based their comparisons on extensive areas which obscured fine patterns of diversity. Since birds respond to the proximate releasers of their habitat (James 1971), not arbitrary geographic blocks, an analysis of local avian communities could provide insights into diversity pertaining to the structure of breeding bird populations. Cook (1969), Tramer (1974a), and Bock and Lepthien (1974, 1975, 1976) have traced the diversity of North American birds to changes in earth history and its subsequent effects on climate, vegetation, and resource availability. These analyses considered relative species richness and disregarded the effects of relative species abundance, or species equitability. My objectives here are to describe and interpret patterns of species frequency distribution within breeding bird communities in North America.