American Goldfinches are found in every land habitat in every season in Ohio. They usually flock together in weedy fields, open flood plains, suburbs, parks, backyard feeders and overgrown areas. They can wander and will move between habitats to locate better food resources. American goldfinches are herbivores who eat almost exclusively seeds, although an occasional insect is consumed inadvertently while eating seeds from asteraceae family (sunflowers, thistle, asters, etc.). Grasses and trees such as alder, birch, and conifers are also a favorite of the American goldfinch. They also consume large numbers of weed seeds. At backyard feeders American goldfinch primarily prefers nyjer (thistle) seed. Flocks will move up to five miles per day between feeders (Middleton 1993).
Sometimes referred to wild canaries, American goldfinches are the only finch that completely molts its body feathers twice a year, once in early spring and again in late fall. In early spring, breeding season, male goldfinch become a vibrant yellow by late fall the yellow feathers turn a tan to olive color. The new fall feathers are much denser than their summer plumage. These soft feathers provide an additional layer of insulation to help keep them warm throughout the winter. Black wings and white wing bars are present throughout the entire year.
American goldfinches breed later than most North American birds. They wait to nest until late July or early August when milkweed, thistle, and other plants have produced fibrous seeds. Their nest is usually assembled in shrubs or saplings in an open setting 4-10 feet above the ground. Females constructs the open cup nest with grass and plant fibers; attaching the nest to the tree or shrub with spider webs. Nests are often woven so tightly that they can temporarily hold water. Females complete the nests by lining them with plant down and hair. It takes females up to six days to build a nest approximately 3 inches across and 2-4.5 inches high.
Female goldfinches usually lay five pale-blue or greenish-blue eggs. They, unlike the male, incubate the eggs. Males feed females on the nest throughout incubation and takes on an ever increasing role in feeding the nestlings as they grow older. Eggs hatch in approximately 12 days. Brown-headed cowbird sometime lay their eggs in the nest of the American goldfinch. The female incubates the egg until it hatches.
However few cowbird chicks live longer than three or four days. This is due to the low amounts of protein found in the vegetarian diet of the goldfinch. American goldfinch nestlings will fledge about 12 days after hatching. Fledglings are dependent on their parents for at least three weeks after leaving the nest.
American goldfinches are abundant and widespread. Populations appear to be stable. However bird populations, including those of the American goldfinch adjust in response to changes in the environment around them. Decreasing amounts of breeding habitats including food and nesting plants, resulting from changing agricultural practices and the expansion of urban areas, may contribute to future population declines.