LOCAL RESOURCE COMPETITION AND SEX-RATIO VARIATION IN BIRDS

We take issue with a recent study by Gowaty (1993) that finds evidence in support of the idea that fledgling sex ratios in birds are influen ced by Local Resource Competition. After controlling for the lack of i ndependence among species due to shared phylogeny, we show that the re lation between fledgling sex ratio and natal philopatry in birds is fa r from statistically significant. From a theoretical perspective, the documented low rate of natal philopatry in birds also makes it unlikel y that parents and their offspring will often compete for resources on the breeding grounds. Thus we argue that there is neither empirical n or theoretical support for the LRC hypothesis to explain tertiary sex ratio variation in birds.