Abstract :
Seventy generally insectivorous riparian bird species in Arizona were studied to determine the effects of communitywise or diffuse interspecific competition in the distribution and abundance of bird populations. The results showed that open-nesting birds avoided experimental plots after addition of boxes. Multivariate analysis showed that this response was true for ecologically diverse species, indicating that communitywise competition is an important determinant of bird distribution and abundance in riparian ecosystems.