Adult Male (Northern)

BASIC DESCRIPTION
North America has more than 50 species of warblers, but few combine brilliant color and easy viewing quite like the Yellow Warbler. In summer, the buttery yellow males sing their sweet whistled song from willows, wet thickets, and roadsides across almost all of North America. The females and immatures aren’t as bright, and lack the male’s rich chestnut streaking, but their overall warm yellow tones, unmarked faces, and prominent black eyes help pick them out.

Habitat	Food	Nesting	Behavior	Conservation

Habitat
Yellow Warblers spend the breeding season in thickets and other disturbed or regrowing habitats, particularly along streams and wetlands. They are often found among willows but also live in dwarf birch stands in the tundra, among aspen trees in the Rockies, and along the edges of fields in the East, where you may find them among alder or dogwood as well as orchards, blueberry bogs, and overgrown power-line cuts. In the West they may occur up to about 9,000 feet elevation. On their wintering grounds Yellow Warblers live in mangrove forests, dry scrub, marshes, and forests, typically in lowlands but occasionally up to 8,500 feet elevation.

Food
Yellow Warblers eat mostly insects that they pick from foliage or capture on short flights or while hovering to reach leaves. Typical prey include midges, caterpillars, beetles, leafhoppers and other bugs, and wasps.

Adult Female (Northern)

Nesting
NEST PLACEMENT
Yellow Warblers build their nests in the vertical fork of a bush or small tree such as willow, hawthorn, raspberry, white cedar, dogwood, and honeysuckle. The nest is typically within about 10 feet of the ground but occasionally up to about 40 feet.

NEST DESCRIPTION
The female builds the nest over a period of about 4 days. First she builds a cup of grasses, bark strips, and plants such as nettles. She places plant fibers, spiderwebs, and plant down around the outside. The inner cup is lined with deer hair, feathers, and fibers from cottonwood, dandelion, willow, and cattail seeds. If a cowbird lays its eggs in a Yellow Warbler’s nest, the warbler often begins building a new nest directly on top of the old one, abandoning both its own eggs and the cowbird’s.

NESTING FACTS

Behavior
Yellow Warblers forage along slender branches of shrubs and small trees, picking off insect prey as they go or briefly hovering to get at prey on leaves. Singing males perch near the tops of the bushes or trees in their territory. As male Yellow Warblers are setting up territories they may perform a “circle flight” in which they fly toward a neighboring male or female in a horizontal, semicircular path. A male may also fly slowly with fast, exaggerated wingbeats away from a female he is courting or a male he is competing with. As these territorial encounters proceed, males start by singing at each other; as the dispute goes on, the songs get quieter or switch to chip notes as the males begin to chase each other. Yellow Warblers typically form monogamous pairs that sometimes last more than one breeding season and reform the next. Yellow Warblers defend their nesting territories from many species, including other warbler species, chickadees, House Wrens, blackbirds, and Eastern Kingbirds. They may even chase off other warbler species while on their wintering grounds. Common predators of Yellow Warbler nests include garter snakes, red squirrels, jays, crows, raccoons, weasels, skunks, and domestic or feral cats.

Conservation
Yellow Warblers are one of the most numerous warblers in North America but their populations have been slowly declining, and have decreased by 25% between 1966 and 2014, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 90 million with 37% spending some part of the year in the U.S., 15% in Mexico, and 57% breeding in Canada. They rate a 6 out of 20 on the Continental Concern Score and are not on the 2014 State of the Birds Watch List. In the western U.S. the grazing of rangelands can degrade Yellow Warbler nesting habitat, particularly stands of willow trees along creeks. The Brown-headed Cowbird lays its eggs in the nests of many species including Yellow Warblers, and this can reduce their breeding success. Like many migratory songbirds that move at night, Yellow Warblers are at risk of collisions with buildings; they can be attracted to and killed at tall, lighted structures such as TV towers and tall buildings.

Backyard Tips
Yellow Warblers eat mostly insects, so they don’t come to backyard feeders. Larger yards that have small trees or are near streams may provide nesting habitat for these birds.

Find This Bird
Listen for Yellow Warblers singing when you’re in wet woods, thickets, or streamsides—they’re one of the most commonly heard warblers in spring and summer. Their song isn’t hard to learn—a tumbling series of whistles that sounds like sweet sweet sweet I’m so sweet. Look for them in the tops of willows and other small trees.