Wild Things: Yellow-rumped warbler (Setophaga coronate)

The Yellow-rumped warbler has a gray head and back and a mottled white breast. The white eye rings stand out against the slate gray head. But the striking features of the bird are the bright yellow throat feathers, the yellow patches at the sides of the breast, and the yellow rump. The male also has a yellow streak on top of the head. The yellow throat is characteristic of the Audubon’s warbler subspecies, which is the most widespread and common race in New Mexico and the U.S. The other race, the myrtle warbler, has a white throat. It may also be found occasionally in New Mexico, but is more common in the eastern U.S.

The breeding range of the Yellowrumped warbler extends from northern New Mexico up the Rocky Mountain range and the Sierras and into Canada, where it encompasses most of that country and also covers most of Alaska. Conifer forests are the preferred habitat, where cup-shaped nests are built, often with feather linings that may cover the eggs. Both parents feed the 45 altricial nestlings, and normally a pair will produce two broods per season.

These warblers migrate to the southern U.S. and into Mexico, being found in open forests and a variety of other riparian, agricultural, or suburban habitats. Because they are able to consume a diverse vegetarian diet, including fruits and berries of many trees and vines, Yellow-rumped warblers are able to survive winters farther north than other warblers. They are the only warbler known to be able to digest the waxy fruit of the wax-myrtle tree, and the myrtle race is named for this unusual ability.

However, Yellow-rumped warblers are primarily insectivores. They are very active and quickly dart out to catch flying insects, forage on the ground, or pick prey off of tree bark or leaves. They will eat caterpillars, beetles, ants, grasshoppers, gnats, aphids, and a variety of other insects, including the spruce budworm, which serves an important ecological service during outbreaks of that insect. They also take spiders and other arthropods.

The song is a quiet trill of about two seconds duration.

Though the population of Yellowrumped warblers is currently abundant, the Audubon Society describes the climate vulnerability status of the Yellowrumped warbler as Moderate, predicting significant losses of breeding range in the Rockies, Sierras, Cascades, and across much of eastern and central Canada as global warming proceeds.