Chipping sparrows return, goldfinches color up

Easily confused for the similar-looking tree sparrow, chipping sparrows (Spizella passerina) are best identified by their chestnut-brown head cap, black eye streak and gray breast feathers. Probably more often heard than spotted, their trilling, single-note song heralds their return to the area from their overwintering territories farther to the south. They are common across the continental United States and Canada during the breeding season, migrating to Mexico, Florida and Cuba for the winter.

Chipping sparrows spend the bulk of their foraging time on the ground, searching for seeds, grasses and greens, though they will readily avail themselves of bird feeders when one is accessible.

Outside of the backyard, they tend to take refuge and build nests in evergreen tree species, though crabapples, maples, honeysuckle vines and large shrubs are also targets for nest building. Nests are fairly flimsy, built thinly of grasses and usually only a few inches deep. Females bear one to three clutches of eggs, and nestlings fledge a scant two weeks after hatching.

A male American goldfinch in mating plumage

Credit: uiowa.edu

Brown-headed cowbirds often target chipping sparrow nests to host their eggs, adding to or completely replacing sparrow eggs with their own for the sparrows to raise. But since chipping sparrows benefit from open areas with trees, their numbers have only increased as humans continue to landscape developed areas, and egg parasitism from cowbirds is unlikely to make a large dent in the chipping sparrow population.

Goldfinches put on their summer paint

It's also molting season for goldfinches (Spinus tristis), which are transitioning from winter to summer plumage. Look for this petite bird at thistle feeders, where they will gravitate until wild seeds and other favorite food sources become readily available in late spring and early summer.

Molting males are unmistakable, with ragged patches of olive-green winter plumage giving way to the vivid yellow color that marks the goldfinch in breeding season. Their short notched tails and dark black wing bars are other easy identifiers.

They are unique in that they are the only native North American finch that undergoes two complete molts every year. In the spring molt, the males put on their bright yellow breeding plumage, while the females have more subdued colors. In the fall molt, both males and females will have subdued colors that help make them inconspicuous through the winter.

Frederick County is well within the year-round range of the American goldfinch, also known as the Eastern goldfinch and wild canary

Cowbirds also parasitize goldfinch nests, but chicks rarely survive more than several days on the goldfinch's all-seed diet; finches dine almost exclusively on the seed of milkweed and thistle and only occasionally consume insects.

Mated pairs build tightly woven nests in branch joints of low shrubs and tangled vines, bearing one to two clutches of youngsters each season. Birds are conspicuous in the summer, with their undulating flight patterns and in-flight twittering song.

Article by Michelle Donahue

Nature Notes for 5/13/2012