The Common Yellowthroat is a small bird, growing up to 15 cm in length. They have olive-brown bodies with bright yellow throats. Males have a dark black mask.
Females and immature Common Yellowthroat do not have a mask, sometimes the female has only a very faint yellow throat. The female bird has a dark bill but the fledgling has a more yellow beak.
They live around grassy marshes or wet meadows. They nest on or near the ground, usually in a clump of grass or low shrub. Sometimes they will even nest inside a skunk cabbage. They will build their nest from a variety of materials like grasses, bark, ferns, and animal hair. A female lays up to 5 brown eggs with black spots. Common Yellowthroat is very careful about their nests. They never fly directly to them, instead, they fly to the ground and then walk to the nest. They leave the same way. This is so predators do not see them around their nests. Eggs hatch in about 2 weeks and young Common Yellowthroat fledge about 10 days later.
They are often bothered by the brood parasitic brown-headed cowbird. A cowbird female will lay her egg in a Yellowthroat nest, letting the parents raise her young for her. The larger cowbird chick gets most of the food at the expense of chicks. Sometimes it even pushes the chicks out of the nest to die.
Common Yellowthroats eat mostly insects and spiders, caterpillars, including tent caterpillars, grasshoppers, dragonflies, beetles, butterflies, and aphids. They do a good job keeping pest insects in check. They do eat some seeds.
Yellowthroat predators include raccoons, mink, and other animals that may find the low lying eggs or nestlings. Adults may be killed and eaten by hawks and owls.