Males weren’t the main players in sex differences in avian plumage
Color evolution among grackles and their kin is not about males showing off their fine feathers. It’s more about females switching their looks, a new analysis indicates.
Among 37 species of grackles, blackbirds and other icterid relatives, males clearly do flash more diverse feather colors than females do, says Jordan Price of St. Mary’s College of Maryland. Bright epaulets on glossy black plumage or shimmering iridescence often give distinctive looks to males. Females, however, just look either generically drab or similar to males.
Scientists have long debated whether today’s sex differences in bird color arose from evolutionary pressures on drab ancestors for males to look sexy. For the grackle group and probably other species, it’s “just not the case,” Price says.
He and Muir Eaton of Drake University in Des Moines, Iowa, worked backward along a genealogical tree of grackle relatives to reconstruct the history of male and female color differences.