Hidden layers of colour in the plumage of tanagers and some other songbirds explain what makes them so eye-catching
By Chris Simms
23 July 2025
Green-headed tanagers are strikingly colourful
Daniel Field
Brightly coloured songbirds called tanagers are so eye-catching because they have a hidden layer of black or white beneath their dazzling plumage.
Painters often prime a canvas with a layer of white to enhance the colours they will eventually layer on, as well as to make it smoother and stronger. But it seems this is a mechanism that birds were using long before humans picked up paintbrushes.
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Rosalyn Price-Waldman at Princeton University and her colleagues have found that when songbirds in the tanager genus Tangara have bright red or yellow plumage, they usually have white layers hidden underneath. When they have blue plumage, they have black layers beneath.
To investigate why, they removed 72 feathers from taxidermied tanager specimens in the Natural History Museum of Los Angeles County’s collection.
By taking pictures of the feathers on different backgrounds, the team measured how their reflectance or absorption of light changed, finding that the underlayers make the top layers look more colourful.