Goldfinches have been coming to the Fields Pond Audubon Center’s bird feeders all summer. The plumage of the males is bright yellow, while the olive green of the females can confuse the uninitiated bird-watcher.

Like the cedar waxwings, goldfinches are finding mates and building nests late in August. The reason for nesting late for both species is similar: both wait until their favorite food is abundant. Cedar waxwings wait for the berries and cherries to ripen, and goldfinches wait until the seeds of the “composites” – members of the aster or daisy family – are abundant and ripe.

Most small songbirds raise their young in May and June and feed them soft green caterpillars and other insects, grubs – larvae of beetles – or worms.

Not goldfinches. They usually wait until August to build their nests. That is a weeklong project, carried out by the female. The nest, soft on the inside, is made of plant fibers and thistle down. The walls of the nest are thick; the nest is often built 10 to 20 feet up in small shade trees in people’s yards.

Once the nest is finished, the female lays one egg per night until five or six tiny blue eggs grace the lovely little nest. The female incubates her eggs for about 12 days.

Meanwhile, the male is out foraging for himself and for the female. He visits the nest about every two hours and feeds her a slurry of seeds from his crop. The crop is a dilation of the esophagus found in many bird species, used to store and-or grind food.

When the eggs hatch, both parents feed the young the slurry of seeds.

The tiny birds grow in the nest for about 12 days. If no crow, blue jay or squirrel plucks them out of the nest and eats them, they fledge. Then the number of goldfinches will grow at bird feeders.

All fall and winter, goldfinches will eat goldenrod, mullein, evening primrose, thistle, birch and alder seeds, in addition to feeding at bird feeders. And the males will have molted into olive green instead of bright yellow, again confusing the uninitiated bird-watcher.

For information on Fields Pond Audubon Center, call 989-2591.