Dan Greaney, Wintu Audubon Society
Published 5:00 a.m. PT Aug. 28, 2020

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This female house finch (left) retains her nest-brown camouflage while the male’s red can brighten with a timely carotenoid-rich diet. (Photo: Larry Jordan, Wintu Audubon Society)

If you have a bird feeder in the continental United States, you have almost certainly been visited by house finches. On both sides of the Mississippi their hungry flocks coat feeders like displays of cherry and root beer lollipops. They park themselves at providential feeding ports or flutter at their neighbors to win better ones. Off the feeders, they are singers who greet mornings with ubiquitous cheery notes, mixing reedy discord with melodious clarity, any time of year. They seem perfectly comfortable making our houses their homes.

House finches fledge from the nest dressed in brown, heavily streaked on their undersides. But as they molt, the males develop a bright red wash over their head, breast and rump. Young females, too, may briefly wear red on their rumps. As adults, females prefer brightly colored males.

Bright colors, however, are not genetically inherited. Like most birds, finches can’t actually make red or yellow pigment. Rather, these molting males incorporate pigments from the foods they eat. In addition to black oil sunflower seeds at feeders, they savor a variety of fruits and vegetables that contain the carotenoids — yellows, reds, and purples — they absorb into feather-paint.

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Saturday August 29, 2020