The scaling of eye size with body mass in birds

Abstract

In species where parental investment is extensive for both sexes, both males and females are predicted to exhibit choosiness when seeking their lifetime partners. Evidence is presented that both courting males and females are choosy in the wood–dwelling, biparental termite Zootermopsis nevadensis. There are, however, sex differences both in the method of mate rejection and in the mate–choice criteria. In particular, females are more likely than males to invite an extra suitor into the nest, whereas males are more likely than females to leave their nest and partner and seek a replacement elsewhere. Correlational analyses of adults show that head width is a mate–choice criterion used by females, whereas body mass and fat mass are used by males. Among males and females that sought replacement mates, those that had been rejected previously were more likely to end up paired with an adult that also had been rejected, compared with adults that had not been rejected. Additional findings reveal a rich repertoire of courting behaviours characterized by extensive intra– and intersexual conflict, including mate rejection, intrasexual combat, and even intrapair aggression.