Red-eyed Vireo in Pennsylvania.

The Red-eyed Vireo (Vireo olivaceus) is a small American songbird. It is somewhat warbler-like but not closely related to the New World warblers (Parulidae).

Adults are mainly olive-green on the upperparts with white underparts; they have a red iris, and a grey crown edged with black. There is a dark blackish line through the eyes and a wide white stripe just above that line. They have thick blue-grey legs and a stout bill. They are yellowish on the flanks and under-tail coverts (though this is faint in some populations). [Wikipedia]

Red-eyed Vireo in Ohio.

A tireless songster, the Red-eyed Vireo is one of the most common summer residents of Eastern forests. These neat, olive-green and white songbirds have a crisp head pattern of gray, black, and white. Their brief but incessant songs—sometimes more than 20,000 per day by a single male—contribute to the characteristic sound of an Eastern forest in summer. When fall arrives, they head for the Amazon basin, fueled by summer of plucking caterpillars from leaves in the treetops. [All About Birds]

Red-eyed Vireo in Pennsylvania.

Red-eyed Vireo Facts [All About Birds]

• The red iris that gives the Red-eyed Vireo its name doesn’t develop until the end of the birds’ first winter. Then the brown iris the birds were born with becomes dull brick red to bright crimson in different individuals.
• On May 27, 1952, Louise de Kiriline Lawrence counted the number of songs sung by a single Red-eyed Vireo seeking a mate on his territory 180 miles north of Toronto. He sang 22,197 songs in the 14 hours from just before dawn to evening, singing for 10 of those hours.
• The Red-eyed Vireo’s magnetic compass guides migration between continents. But fat stores seem to influence migration paths when the birds encounter the Gulf of Mexico. Fatter birds head across the Gulf, while leaner birds hug the coastline or travel inland around the Gulf. Cloud cover also makes routes near land more likely.
• The oldest known Red-eyed Vireo was at least 10 years, 2 months old when it was recaptured and re-released during banding operation in Maryland.