Why did double molting help male ducks develop bright breeding plumage?

The double molt in anseriforms is an evolutionary adaptation that allows male ducks to develop striking nuptial plumage. This bright breeding plumage serves a critical biological function: it helps prevent interspecific hybridization in environments where many different species of ducks coexist.1

By undergoing a double molt, males can transition into this specialized, vibrant appearance specifically for the breeding season, while adopting a duller, protective eclipse plumage during the summer months. This cycle ensures that males are visually distinct during the mating period, which is essential for species recognition and successful reproduction.231