Yellow-rumped warbler

Appearance

The yellow-rumped warbler has an average length of 14 cm and weight of 12.5 g, its appearance is known to be different across its subspecies groups, especially the two major ones: the coronata group and the "auduboni" group; intra-group variations are also observed. In spite of varying appearances, the yellow rump is present in all subspecies and thus characterizes the yellow-rumped warbler. Within the myrtle warbler group, adult males during the breeding season have gray backs with dark streaks, while females have brown backs in contrast; male and female myrtle warblers can also be distinguished by their different cheek colors, with the former's being black and the latter having brown or gray cheeks. The Audubon's subspecies group is not very dissimilar to the myrtle: in summers, males of both forms have streaked backs of black on slate blue, white wing patches, a streaked breast, and conspicuous yellow patches on the crown, flank, and rump. Yet the color of the "coronata" and "auduboni" groups' throat patches differs and distinguishes them, as the Audubon's warbler sports a yellow throat patch while the myrtle warbler has a white throat and eye stripe, and a contrasting black cheek patch. Females of both forms are more dull, with brown streaking front and back, but still have noticeable yellow rumps. Goldman's warbler, found in Guatemala, resembles Audubon's but has a white lower border to the yellow throat and otherwise darker plumage; males replace the slate blue of Audubon's with black.

Comprising most of the species of the New World warbler family, among the genus "Setophaga", the yellow-rumped warbler is a mid-to-large sized species. The total length of the species can range from 12 to 15 cm long, with a wingspan of 19 to 24 cm. Although the length is only slightly greater than other "Setophaga" warblers, it can be mildly to significantly heavier than most other North American species, although blackpoll warblers are slightly larger still. Body mass can vary from 9.9 to 17.7 g, though averages between 11 and 14 g. Among standard measurements, the wing chord is 6.3 to 8.4 cm, the tail is 5 to 6.6 cm, the bill is 0.8 to 1.1 cm and the tarsus is 1.8 to 2.2 cm.

Naming

The genus name "Setophaga" is from ancient Greek "ses", "moth", and ', "eating", and the specific "coronata" means "crowned".

Distribution

The yellow-rumped warbler breeds from eastern North America west to the Pacific, and southward from there into Western Mexico. "Goldman's" yellow-rumped warbler is a non-migratory endemic within the highlands of Guatemala and the black-fronted warbler is also a non-migratory Mexican endemic. The myrtle and Audubon's forms are migratory, traveling to the southern U.S., Mexico, Central America, and the Caribbean for winters.

Food

Audubon's and the myrtle are among North America's most abundant neotropical migrants. They are primarily insectivorous. The species is perhaps the most versatile foragers of all warblers. Beyond gleaning from leaves like other New World warblers, they often flit, flycatcher-like, out from their perches in short loops, to catch flying insects. Other places yellow-rumped warblers have been spotted foraging include picking at insects on washed-up seaweed at the beach, skimming insects from the surface of rivers and the ocean, picking them out of spiderwebs, and grabbing them off piles of manure. Common foods include caterpillars and other larvae, leaf beetles, bark beetles, weevils, ants, scale insects, aphids, grasshoppers, caddisflies, craneflies, and gnats, as well as spiders. They also eat spruce budworm, a serious forest pest, during outbreaks.

When bugs are scarce, the myrtle warbler also eats fruit, including the wax-myrtle berries which gave it its name. It is the only warbler able to digest such waxy material. The ability to use these fruits allows it to winter farther north than other warblers, sometimes as far north as Newfoundland. Other commonly eaten fruits may include juniper berries, poison ivy, poison oak, greenbrier, grapes, Virginia creeper and dogwood. They eat wild seeds such as from beach grasses and goldenrod, and they may come to feeders, where they'll take sunflower seeds, raisins, peanut butter, and suet. On their wintering grounds in Mexico they've been seen sipping the sweet honeydew liquid excreted by aphids. Male yellow-rumped warblers tend to forage higher in the trees than females do. While foraging with other warbler species, they sometimes aggressively displace other species, including pine warblers and Blackburnian warblers.