Vegetation Structure and Avian Diversity in Several New World Areas

Abstract

Data on avian community structure and vegetation structure for Illinois, Panama, Texas, and Bahama study areas are discussed. Bird species diversity is linearly related to foliage height diversity and sigmoidally related to the percent vegetation cover. Under some circumstances, the volume of vegetation in addition to the layering and distribution among the layers is important as a predictor of bird species diversity. Historical factors seem to be of importance in some phases of the evolution of avian diversity. Horn's Rh, an inverse measure of overlap, applied to tropical and temperate bird and vegetation data, and other considerations indicate that horizontal habitat selection is more precise in mature tropical habitats than in temperate or less mature tropical habitats. These differences are attributed to restriction of species to narrower adaptive peaks in diverse faunas than in less diverse ones. Data indicating more precise vertical habitat selection in tropical habitats are more equivocal. Earlier suggestions of increased microspatial heterogeneity in homogeneous tropical habitats as compared with similar temperate areas, and distinctions between standing crop diversity and existence energy diversity regressed on foliage height diversity are not substantiated.