A medium-sized warbler with a relatively wide, flat bill and fairly long, expressive tail. In flight it has a deep chest, slim belly, and long, somewhat club-shaped tail. American Redstarts measure 11 to 13 centimeters in length, with a wingspan of 16 to 19 centimeters. Adult male American Redstarts are mostly black with bright orange patches on the sides, wings, and tail. The belly is white. Females and immature males replace the orange with yellow or yellow-orange. They have gray head and underparts, with olive back and wings and dark-gray tail. These birds are incredibly active insectivores that seem never to stand still. They rapidly spread their cocked tails, exposing the orange or yellow in a quick flash, which often startles insect prey into flushing, whereupon the redstart darts after it, attempting to catch it in the air. American Redstarts breed in open wooded habitats, particularly those dominated by deciduous trees. In migration, the species can be found in nearly any treed habitats. Its tropical winter habitat is in woodlands and open forest at lower and middle elevations. This species is of low conservation concern.
- The American Redstart flashes the bright patches in its tail and wings. This seems to startle insect prey and give the birds an opportunity to catch them.
- Young male American Redstarts have gray-and-yellow plumage, like females, until their second fall. Yearling males sing vigorously in the attempt to hold territories and attract mates. Some succeed, but most do not breed successfully until the following year when they develop black-and-orange breeding plumage.
- The oldest American Redstart lived to be over 10 years old.