Most of Georgia’s neo-tropical migratory birds have wrapped up -- or nearly wrapped up -- their nesting seasons. The orchard oriole and several warbler species already are heading south for the winter. Ruby-throated hummingbirds and others soon will follow.
The songbirds that are still nesting -- bluebirds, Northern cardinals, American robins -- are rearing their second, third, perhaps even fourth broods of the year.
An exception is the American goldfinch, which usually commences nesting for the first time in July or as late as mid-August, and continues to nest through late September. Known for the brilliant yellow breeding plumage of the male, the cheery little goldfinch breeds mostly north of the fall line in Georgia.
The reason for the goldfinch’s delayed breeding is poorly understood, but ornithologists believe it's timed to late summer seed-ripening. The goldfinch is unusual among Georgia songbirds in that its diet consists almost exclusively of grass, flower and tree seeds, which are starting to mature now in great abundance. Rarely does the goldfinch eat insects.
Ornithologists believe the goldfinch’s nesting season is particularly timed to the ripening of thistles. Not only do goldfinches relish thistle seeds, they also heavily line their nests with soft thistledown. In painting the goldfinch, artist John James Audubon portrayed a pair feasting on pink-flowered bull thistles. Birders say that when you see thistles going to white puffs of down, it's goldfinch-nesting time.
Goldfinches will visit feeders stocked with commercial thistle seeds and black oil sunflower seed. In addition, sunflowers, zinnias, tickseed, coneflowers and a variety of other common garden plants will attract the birds when the flowerheads go to seed.
The female goldfinch builds a tightly woven, cup-shaped nest of weed stems, grasses, shreds of bark, dried flowers, spiderwebs, hair and thistledown in the fork of a shrubby tree -- usually a hawthorn, serviceberry, maple or sapling pine -- 1 to 30 feet off the ground. Breeding habitat typically is weedy fields or open woodlands with shrubs.
The female lays four to six pale blue eggs that are incubated for 12 to 14 days. The male feeds his mate on the nest. The female feeds the young regurgitated seeds. Nestlings fledge after about 15 days; the parents then continue to feed the begging fledglings for up to three more weeks.
Because of their late nesting, goldfinch pairs usually produce only one brood per season. To permit a second nesting, a female may abandon the first brood to the care of her mate, and then leave to find another mate to start a second brood.
In the sky: The moon will be new Saturday night, a thin crescent low in the west just after dark, said David Dundee, astronomer with Tellus Science Museum. Mercury sets in the west just after dark. Mars is in the east about three hours before sunrise. Jupiter rises out of the east around midnight. Saturn is low in the west at dark and sets in the west before midnight.
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