Courtesy Kenn Kaufman
With the exception of dry, southwestern desert areas, the Common Yellowthroat breeds across the United States and most of Canada. This warbler winters from the Carolinas south through southern Texas and Central America to Colombia and throughout much of the Caribbean. In most of western California, Common Yellowthroats can be found year round. Populations are densest in extensive wet, shrubby habitats.
A legend for the range map to the right can be found here
Common Yellowthroats breed and winter in a wide variety of damp habitats with low, dense vegetation. Bogs, swamps, low-lying weedy areas, and the damp, brushy edges of woods attract them. Throughout the year, Common Yellowthroats are almost always near the ground, with the notable exception of males during their skylarking display flight. Their genus name, Geothlypis, means "ground bird."
Hopping and climbing through thickets and weeds, the Common Yellowthroat searches the ground and plants for spiders, insects, and caterpillars. Mostly, this warbler picks food from surfaces, but will also chase prey on the wing.
Common Yellowthroats produce one to two broods per year. Males arrive on territory about a week before females and begin defending it with songs, calls, and chases. Pairs bond for the season after a brief courtship, and the female builds a nest on the ground or higher in dense vegetation, where water may swamp the eggs.
The nest is a layered cup of grasses, becoming finer at the center. The female lays 3 to 6 whitish eggs, splotched with brown and gray, and incubates them for about 12 days. Males sometimes feed incubating females at the nest. Both parents feed the helpless, naked young until they fledge in about 12 days. Fledglings receive care for up to 35 days.
Cowbirds often lay their eggs in the nests of Common Yellowthroats; rates of parasitism reached 47% in one Michigan study. The warbler has a variety of defenses, including the removal of cowbird eggs, abandonment of the nest, and construction of a new nest over the cowbird's eggs.
Most Common Yellowthroats migrate at night over short and long distances, departing their wintering grounds through April and into May. Many cross the Gulf of Mexico, rather than fly along the coast. Most Common Yellowthroats depart the breeding grounds at about the same time for a protracted migration southward.