PHYLOGENY AND THE RELATIONSHIP BETWEEN BODY-SIZE AND ABUNDANCE IN BIRD COMMUNITIES

1. Within local bird communities, relationships between body size and abundance across the subtaxa within lower-level taxa (such as species within genera) are no more likely to be positive than those across the subtaxa in higher-level taxa (such as suborders within orders). 2. The species within tribes of birds which have no close relatives in the world tend to show positive relationships between body size and population abundance. However, the relatedness of the tribe to others in its community is not a significant predictor of the sign of the body size-abundance pattern. 3. The date at which the species last shared a common ancestor is a better predictor of the size-abundance pattern than is the relatedness of a tribe to other birds in the world. 4. The patterns do not appear to hold for Passeriforme birds, possibly because there is little variation in the dates of origin and radiation among passerine tribes. 5. It has been suggested that tribes containing fewer different lifestyles (and which therefore are likely to be direct competitors with each other) will be those that tend to show positive size-abundance relationships. Hence, the length of the entry for a tribe in Austin's (1961) handbook of birds of the world is a statistically significant predictor of the sign of the relationship between body size and abundance, independently of the number of species in the tribe.