Morphological variation in a population of grey-crowned babblers: Correlations with variables affecting social behavior

Summary Variation in weight, wing length and bill length in a population of grey-crowned babblers is influenced primarily by sex and age, but correlations with size of social unit, with reproductive success, and with vegetation are also detectable (Table 1). The latter correlations vary with sex, age, and status as helper or breeder. Differential wear according to behavioral role, competition for status, incubation, and inheritance are discussed as possible causal mechanisms. Helpers were not detectably smaller in any dimension than breeders of the same age and sex. Male and female non-breeding helpers differ in patterns of morphological correlation, suggesting that they have different behavioral roles. Breeding males have a unique pattern of morphological correlation, suggesting that their foraging behavior differs from breeding females and non-breeders.