Article for May - June 2013
For Wildlife Watchers: American Goldfinch
by Rob Simbeck
photograph by Phillip Jones
A goldfinch is a bird whose eye-popping male looks rather like a marshmallow peep, helping to earn the species the nickname "wild canary."
When it comes to goldfinches, the place to start may well be with the collective term. Turkeys and swifts come in flocks, geese in gaggles, quail in coveys and hens in broods, but a group of goldfinches is known as a charm, and there are few appellations more fitting. This is a bird whose eye-popping male looks rather like a marshmallow peep, helping to earn the species the nickname "wild canary." Their antics en masse moved John J. Audubon to lovingly appreciative prose. Noting that a migratory group will "alter its course at the calling of a single one perched on a tree," he wrote: "No sooner has the flock, previously on wing, alighted, than the whole party plume themselves, and then perform a little sweet concert."
Males are particularly photogenic after a spring molt that leaves them in breeding plumage — a brilliant yellow, set off by a jet-black cap and black wings with white stripes, and a white undertail. This bright coloration that shows off the male's relative health and genetic desirability draws on raw materials in its diet. According to Arizona State University Associate Professor of Evolutionary Biology Dr. Kevin McGraw, seeds and other plant material eaten by the goldfinch contain carotenoids, pigments that color plants and animals. In the goldfinch, carotenoids from their diet are used at the feather follicles themselves to manufacture two other yellow carotenoids, and both the ingested and manufactured pigments are responsible for that bright, lemon-yellow breeding plumage. Another pigment, called eumelanin, which is synthesized in the feathers from amino acid precursors also found in the goldfinch’s diet, is responsible for the bird's black feathers. McGraw cites a 1993 study reporting that female finches look in particular for males with large black caps.
American Goldfinch -
Spinus tristis (thorny plant, sad — for the thistle and its call)
Description: Five inches long with a nine-inch wingspan. Breeding male is bright yellow with a black cap and black wings with white stripes. Females and winter males are a drabber olive-yellow.
Range and Habitat: Prefers weedy areas. In South Carolina, more common inland than on the coastal plain. Breeding range from Canada through most of U.S. and parts of Mexico. Migratory in northern parts of range.
Reproduction: Among the latest-breeding species, from June to September. Female lays four to six light blue eggs, which hatch in two weeks. Young fledge at about fourteen days.
Viewing Tips: Distinctive and widespread. Found especially in fields. Will come to feeders with sunflower or nyjer seeds. Watch for undulating flight, with calls on the upstroke.
Evolutionarily, it pays for the females to be less conspicuous as they sit on the nest, and that's definitely the case for goldfinches. In their understated breeding plumage, female goldfinches are a yellowish brown on top and bright to dull yellow underneath, with light wing bars, a light bill and a black tail with white tips.
Goldfinches are common sights at many feeders, coming particularly for sunflower and nyjer seeds, but they eat a range of field and garden flowers too, from dandelions, mullein and milkweed to sunflowers and asters, as well as some tree and grass seeds. They have a particular affinity for thistles. They are tailor-made for an acrobatic approach to dining, grasping plant stems and seed heads with claws at the end of long legs and using their conical beaks to remove seeds.
Seeds are, in fact, vital to every aspect of goldfinch life. Goldfinches have one of the latest reproductive cycles of any South Carolina bird, beginning in June once thistles and milkweed, which goldfinches rely on for food and nesting material, have flowered and produced seeds.
"I've had a pair of goldfinches bring their young, who still had down in the feathers on their heads, to the feeder in mid-September," says Lex Glover, a wildlife technician with the S.C. Department of Natural Resources, "so I know they nest late."
Highly social birds, goldfinches don’t defend territories until they begin mating behavior. A male will circle the perimeter of a preferred territory, flying from perch to perch with an exaggerated version of normal flight. The brilliant plumage flight displays are part of a package designed to attract females. When one accepts, the male will sing as they fly together in wide circles. The pair chooses a site, and the male helps carry material as the female spends the better part of a week building a three-inch-wide, cup-shaped nest in the fork of a tree or shrub, lashing it to a branch with spider web and cocoon silk, and lining it with thistle down. The nest, generally no more than fifteen feet off the ground, can be woven so tightly it will hold water.
The female lays from four to six light blue eggs, each scarcely larger than a peanut, and incubates them for twelve to fourteen days while the male regurgitates seeds to feed her. The chicks are born blind and naked, weighing just a gram or so. Both parents then defend the nest and feed the young, which develop quickly, opening their eyes at three days and feathering out at two weeks. They can take short flights by that point, but stay close by and remain dependent on their parents for up to a month. The late, short nesting season means there is usually only one brood, but occasionally the female will leave the nest to the male, find another and establish a second nest.
After breeding season, adults molt into more subdued winter plumage. The male is a muted gray and brown, with yellow on the face and throat and a white lower belly; the female is grayish with less distinct wing bars and a darker bill. Those in northern latitudes prepare to move to winter grounds, following food supplies in large foraging flocks, which may include redpolls and pine siskins and can number hundreds of birds. They may be seen in large roosts, calling back and forth.
"In wintertime," says Glover, "they may add maple seeds to their diet and I regularly find them pulling the seeds out of sweetgum balls. I don't have sweetgum in my yard, but one year I cut some limbs from a tree in a field nearby and laid them across branches in my oak tree. The birds jumped all over them."
Wintering flocks mean South Carolina's goldfinch population is higher in the winter than in the summer, although Glover says, "the largest numbers are at my feeders in February, March and April, when they start to move north in the spring."
Humans, in general, have been good for goldfinches. Forest clearing provides fields more likely to provide the plants they need, and our feeders are major sources of food. We are more than repaid in that they eat plenty of weed seeds and by their beauty and the pleasant per-chick-o-ree call that often accompanies their undulating flight. States as widely placed as New Jersey, Iowa and Washington have named the goldfinch their state bird. Its predators include snakes, domestic and feral cats, squirrels and some other birds, including blue jays and kestrels, but goldfinches are doing well range-wide, and given all the attractive attributes this small bird brings together, that's a very good thing for wildlife watchers everywhere.
Rob Simbeck has been writing SCW's "For Wildlife Watchers" column since 1994.
© 2013 South Carolina Wildlife Magazine, March - April 2013 - www.scwildlife.com