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. Back to top
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. Back to top
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.
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.
|Clutch Size:||1-7 eggs|
|Number of Broods:||1-2 broods|
|Egg Length:||0.6-0.8 in (1.5-2.1 cm)|
|Egg Width:||0.5-0.6 in (1.2-1.6 cm)|
|Incubation Period:||10-13 days|
|Nestling Period:||9-12 days|
|Egg Description:||Grayish or greenish white with dark spots.|
|Condition at Hatching:||Helpless, with light-gray down, weighing about 1/20 of an ounce.|
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.Back to top
Yellow Warblers are one of the most numerous warblers in North America, but their populations have been slowly declining by an estimated 0.4% per year for a cumulative decline of about 20% between 1966 and 2019, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 97 million and rates them 8 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. In the western U.S., the grazing of rangelands can degrade Yellow Warbler nesting habitat, particularly among 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 can be attracted to and killed by collisions with tall, lighted structures such as TV towers and tall buildings.Back to top
Lowther, Peter E., C. Celada, N. K. Klein, Christopher C. Rimmer and D. A. Spector. (1999). Yellow Warbler (Setophaga petechia), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.
Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.
Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.
Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2019). The North American Breeding Bird Survey, Results and Analysis 1966–2019. Version 2.07.2019. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.
Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.
Stephenson, T. and S. Whittle (2013). The Warbler Guide. Princeton University Press, New Jersey, USA.