The spectacle of spring is upon us- birds singing, flowers blooming, bees buzzing. And though you may not be aware, there are romantic dramas to rival the latest season of Downton Abbey taking place in your backyard. Will Lady Mary choose Lord Gillingham or Charles Blake? If she were a House Finch, she would be flitting off into the bushes with whichever man had the reddest feathers.
Like Lady Mary, female house finches are practical. They are looking for a mate that offers concrete benefits to their potential offspring, not simply charm or good times. Though female House Finches are a drab brown, they size up potential mates by color. Male House Finches sport yellow, orange or red feathers on their head, breast and rump. In the eyes of the females, redder is better. Female finches, as well as biologists, consider the redness of a male house finch’s feathers to be an honest indicator of his quality. The red color of these feathers is due to carotenoid pigments, including the familiar beta-carotene. House finches cannot produce these pigments themselves, instead they must get them from the foods that they eat. The more carotenoid rich foods a male eats, the redder feathers he can produce. Males that cannot find enough food rich in these pigments will only be able to produce feathers that are yellow or orange, rather than fiery red. So the redness of a male’s feathers indicate his talent as a forager, talent that may be passed along to his offspring.
A male’s color also tells females about his immune system. House finches, like all animals, are infected by many kinds of parasites. (Not to worry, bird parasites are generally not transmissible to humans.) These parasites can affect a male’s ability to use the carotenoids in his diet to produce red feathers. If a male is heavily infected with parasites, the feathers he produces will be paler, even if his diet is rich in carotenoid pigments. So a male’s redness gives females clues about his health and ability to fight off infections. If a female mates with a redder male, her offspring may inherit his superior immune system.
Biologists have found that male color is important to female birds in many other species, including the American Goldfinch, which is also common at feeders in the Grand Valley. In the case of the Goldfinch, females are on the lookout for bright yellow males. Like the House Finch, Goldfinches get their yellow feather color from carotenoid pigments their diet- in this case yellow carotenoids, like lutein, rather than red ones.
So the next time you watch the goings on at your feeder, see if you can spot the most eligible bachelor. He’ll be the House Finch with the scarlet chest or the Goldfinch as bright as a dandelion. Then sit back and watch the show.
Try This Trick at Home
If you want to have the sexiest House Finches on the block, you can try this little experiment: Put a little finely chopped carrot peel, shredded carrots or sweet potatoes out near your bird feeder. These vegetables are rich in the carotenoids House Finches need to produce redder feathers. Biologists have provided these foods to House Finches in experiments to increase their redness and apparently the birds loved them. The time to try this is in the late summer and early fall. That is when the finches are going through molt, dropping all their old feathers and replacing them with new ones. Dietary carotenoid pigments are most important when they are growing this new set of feathers. Once the feathers are produced, their color doesn’t change until they molt the following year.
An edited version of this post first appeared in the Grand Junction Daily Sentinel on Tuesday April 8, 2014. You can check it out here: http://www.gjsentinel.com/outdoors/articles/the-handsome-house-finch