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. Th e species within tribes of birds which have no close relatives in the world tend to show positive relationships between body size and popula tion 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 com mon 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 patt erns do not appear to hold for Passeriforme birds, possibly because th ere is little variation in the dates of origin and radiation among pas serine tribes. 5. It has been suggested that tribes containing fewer d ifferent lifestyles (and which therefore are likely to be direct compe titors 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 sig nificant predictor of the sign of the relationship between body size a nd abundance, independently of the number of species in the tribe.