Photo: House Finch, Philip Sonier
Mr. House Finch You Are What You Eat
By Jessica Biggers
Years ago, I remember sitting in a boat on an estuary in the Celestun Biosphere in Mexico, completely mesmerized by the vast flock of American Flamingos feeding on shrimp on the salt flats. They were magnificent, and the first thing I thought when I saw them, was how different they looked from the pink flamingos at the zoo. These wild flamingos displayed more of an orangish pink hue; due to the type of shrimp they consumed.
To see this amazing act of nature in flamingoes, you must visit Mexico, Central American, South America or the Caribbean. But you can also witness this effect on plumage color closer to home. One bird in particular, the male House Finch, can range in color from yellow to bright red based on the food he eats. The fruits these males consume contain carotenoids, which directly contribute to how yellow or red their feathers become. Most male House Finches show off their red head, rump and headband, but if you look closely, some have a more orange or even yellowish hue. So, as the saying goes, “You are what you eat,” at least when it comes to the color of one’s plumage.
Eastern House Finches eat a variety of seeds and fruits, including mustard seeds, knotweed, thistle, mulberry, poison oak and more. They also forage in orchards eating cherries, apricots, peaches, pears, plums, strawberries and blackberries. Bird feeders provide an additional supply of food, specifically black oil sunflower, millet, milo and some colorful dried fruits as well. The redder the fruit – the redder the bird.
Since female House Finches tend to select males that are bright red, research has shown that some males tend to be selective in the fruit and seeds that they eat. In a study back in 2009, researchers offered male House Finches different colored sunflower seeds. These males had a choice between green, yellow, orange and red colored seeds. Males tended to avoid yellow-dyed sunflower seeds and preferred the red and green ones. Males who are not as picky about what they eat may find it difficult to attract and court a female during breeding season.
Even though many male House Finches will prefer fruits that are red, sometimes there isn’t enough to go around. So, they eat what they can get. This may explain why in some areas there may be more yellow or orange-colored House Finches bopping around.
Surprisingly, there are many other local bird species whose color and brightness comes from the carotenoids they get from eating a variety of fruits and seeds. These include Northern Cardinals, American Goldfinches and yellow-hued warblers. However, unlike the House Finch, most of the fruits and seeds these guys consume may affect how dull or bright their plumage is rather than displaying a different shade of color.
Read more from our Bird of the Month series here.
Sources:
https://academy.allaboutbirds.org/how-birds-make-colorful-feathers/