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Ask a Birder: When birds adopt their breeding plumage, is that through developing new feathers or changes in the existing feathers?

March 26, 2025 by Kai Pflug 1 Comment

This is a more interesting question than it may first seem. For most birds, molting into new feathers is the typical case. These birds replace their old feathers with new and usually more colorful ones that are better at attracting mates (think of dressing up before going for a night out). Usually, this change happens shortly before the breeding season.

Red-necked Phalarope, non-breeding plumage (cover photo shows breeding plumage)

However, there is also the case of a color change of existing feathers. One way this can occur is via the wearing away of feather tips – the sparkling colors of the European Starling develop this way. This is a gradual process reaching its peak in time for the breeding season.

There even is an example of deliberate staining of feathers in time for the breeding season. Bearded Vultures have naturally pale or whitish body feathers, but during the breeding season, they intentionally bathe in iron-rich mud or water, which stains their plumage a deep rusty orange or reddish color. This behavior probably plays a role in mate attraction, as more intensely colored individuals tend to be higher-ranking.

You may also read that hormonal changes can lead to color changes in existing feathers – but that is incorrect. Feathers are dead structures and thus cannot change color through hormonal activity alone.

So, while most breeding plumage is adopted via the replacement of feathers, other pathways for changing the feather colors exist.

Written by Kai Pflug
Kai has lived in Shanghai for 21 years. He only started birding after moving to China, so he is far more familiar with Chinese birds than the ones back in his native Germany. As a birder, he considers himself strictly average and tries to make up for it with photography, which he shares on a separate website. Alas, most of the photos are pretty average as well.He hopes that few clients of his consulting firm—focused on China’s chemical industry—ever find this blog, as it might raise questions about his professional priorities. Much of his time is spent either editing posts for 10,000 Birds or cleaning the litter boxes of his numerous indoor cats. He occasionally considers writing a piece comparing the two activities.