Bird of the Week: American Goldfinch

from Wildlife Promise

American goldfinch by Lara Hardesty

A male American goldfinch perches in Block Creek Natural Area near Comfort, Texas. Photo by Lara Hardesty.

A few years ago, the editors of National Wildlife magazine asked readers to vote for which North American bird species they’d most like to see. In the emails and letters that followed, the number one choice, by far, was the American goldfinch. It’s easy to see why: Although data compiled by the Cornell Lab of Ornithology’s Project FeederWatch shows that the goldfinch is among the most common backyard birds nationwide, it also is one of the most brightly colored—especially this time of year when the songbirds are just beginning their breeding season.

Starting in spring and continuing through much of summer, male goldfinches are a bright lemon yellow with black foreheads, black wings and white markings above and beneath their tails. (Females are olive above and dull yellow beneath.) Come winter, both sexes turn a drab brown—so dull they often are mistaken for sparrows. The change occurs through the process of molting. According to the Cornell lab, the American goldfinch is the only finch species that molts its body feathers twice a year, once in late winter and again in late summer.

Late Breeders

Frequent molting is both time-consuming and physiologically taxing for the birds. Some scientists suggest this may be the reason goldfinches breed so late in the season—rarely beginning in earnest until mid-July. Another possibility is that the birds wait to nest until thistle, milkweed and other plants have produced fibrous seeds, which goldfinches not only eat but also use to build their nests.

According to Cornell, “goldfinches are among the strictest vegetarians in the bird world, selecting an entirely vegetable diet and only inadvertently swallowing an occasional insect.” This diet helps protect goldfinches from cowbirds: Though the parasitic birds may lay eggs in goldfinch nests, the hatchlings cannot survive long on an all-seed diet.

Color and Fitness

Like backyard bird-watchers, some scientists also are intrigued by the goldfinch’s striking color. For the past decade, Keith Tarvin and colleagues at Oberlin College in Ohio and Trinity University in Texas have been studying the relationship between color, status and sex in the lives of the birds. They’ve discovered that choosy female goldfinches prefer to mate with males that have the brightest plumage. “Color matters,” says Tarvin.

Why? One possibility stems from the fact that the male’s color comes from carotenoid pigments (the chemicals that make carrots orange) that he acquires through his diet. Tarvin suggests that by selecting the brightest males, females also may be getting the best food providers for their offspring.

Backyard Tips

Enticing goldfinches is easy. During winter, they’ll show up by the dozens at almost any kind of feeder.  In summer, the birds also visit backyards, but in smaller numbers. Niger (also called thistle) seed is their favorite, but goldfinches will devour black oil sunflower seeds as well. Gardeners also can lure them in by growing native sunflowers, thistles, goldenrod, coreopsis, elm and alder. These plants are important sources of food, and female goldfinches use thistledown to line their nests.

Make your yard more attractive to goldfinches and other birds by turning it into an NWF Certified Wildlife Habitat!

Voice: Song is a pleasant jumble of distinct, high, sweet, tinkling notes, usually with paired phrases. Flight call is a sweet pe-CHI-pee-pee.

Sources: Going for the Gold” by Doreen Cubie, National Wildlife, August/September 2010; Cornell Lab of Ornithology’s All About Birds and National Wildlife Federation Field Guide to Birds of North America.