THE RELATION BETWEEN BODY-SIZE AND ABUNDANCE IN A BIRD COMMUNITY - THE EFFECTS OF PHYLOGENY AND COMPETITION

Within a bird community in North America, abundance patterns correlate with the evolutionary history of the species. Tribes of birds which h ave no close relatives (ancient lineages) tend to have positive relati ons between size and abundance, i.e. larger species are more abundant than smaller ones. This is not true of less ancient tribes. Interspeci fic competition has been suggested as the explanation for such pattern s and, for the first time, it is possible to test this hypothesis. Anc ient tribes are those in which interspecific competition is found to b e strong, and the strength of competition correlates significantly wit h the abundance patterns of tribes.