Canopy dwelling, caterpillar-eating summer songster. Common East of Rockies and into Pacific Northwest in summer; winters in South America. Medium, stocky songbirds; olive above, pale below with yellow undertail wash; contrasty gray cap and eyestripe. Prefers deciduous forest, where it deliberately feeds on insects, especially caterpillars, in summer; more berries in fall and winter. Often obscured in treetops, but Incredibly, monotonously vocal throughout the day – one bird studied sang over 20,000 times in a day. Nests bound with spider-web glue, often in a low- to mid-story tree fork; nests commonly parasitized by Brown-headed Cowbird. Lifespan up to 10 years. Population ~ 180 million and increasing.