Male birds typically outshine the females, but in some cooperative breeders females have evolved to outshine the males.
Darwin noted that sexual dimorphism (differences in male and female traits) generally leads to elaborate-looking males and dull females because reproduction is shared more equally among females than males. As a result, males need fancy duds to compete with other males for the attention of female mates.
In some species, however, females compete as intensively as males for reproductive opportunities. This takes place among species that live in family groups, known as cooperative breeders, in which not all individuals have the chance to reproduce. Scientists believe that in many cooperatively breeding species, not only does reproduction vary inequitably among males, but also among females. Because of this unequal reproduction among both sexes, females must also compete for reproductive opportunities.