| Yellow-rumped Warbler | |
|---|---|
 Male Myrtle Warbler (Setophaga coronata coronata) | |
| Information | |
| Range | North and Central America |
| Scientific Classification | |
| Kingdom | Animalia |
| Phylum | Chordata |
| Class | Animalia |
| Order | Passeriformes |
| Family | Parulidae |
| Genus | Setophaga |
| Species | S. coronata |
| Conservation Status | |
 Least Concern | |
The Yellow-rumped Warbler impresses with it's sheer numbers during spring and fall migration. It's extensive distribution connects Panama to the Arctic Circle, an ability which they owe to being the only warblers that can digest the wax on wax-coated berries.
Classification[]
The species was often considered as two separate species, the "Myrtle" and "Audubon's". Since 1973, the American Ornithologists Union had elected to merge the two species on the basis that the two groups interbreed freely where they intergrade.
In 2017, a proposal was made to split the Yellow-rumped Warbler into separate species.
In contrast, the International IOC World Bird List v. 10.2 classifies the myrtle, Audubon's, and Goldman's as separate species (Setophaga coronata, Setophaga auduboni, and Setophaga goldmani, respectively), and the black-fronted warbler as a subspecies of S. auduboni. Proper taxonomic treatments remain a matter of debate.
Evolution[]
The Myrtle form was apparently separated from the others by glaciation during the Pleistocene, and the Audubon's form may have originated more recently through hybridization between the myrtle warbler and the Mexican nigrifrons form.
The divergent populations probably came into contact again about 7500 years ago and now interbreed where their ranges meet, in the passes of the Canadian Rockies. Due to the interbreeding in this area, the hybrid zone extends 150 km in either direction and will probably continue to grow as time passes. It has been calculated that it will take more than 6 million years for these taxa to completely fuse.
Taxonomy[]
The genus name Setophaga is from ancient Greek ses, "moth", and phagos, "eating", and the specific coronata means "crowned". The scientific name of this warbler was introduced by Carl Linnaeus in 1766.
There are four recognized subspecies:
- Myrtle Warbler S. c. coronata (Linnaeus, 1766) - migratory bird subspecies that inhabits the boreal forests of the east side of North America. Myrtle warblers have a white throat, white eyebrow, and lack wing patches between their white wing bars. Juvenile Myrtles have more extensive pale throats than Audubon's.
- Audubon's Warbler S. c. auduboni - migratory; inhabits the mountainous west coast of North America. Unlike the Myrtle Warbler, they possess a yellow throat and no eyebrows. Males have a significant amount of white between the wing-bars. Immature birds are dull brown with yellow on their rumps and flanks, but lack yellow on their throats and heads.
- Black-fronted Warbler S. c. nigrifrons – non-migratory Mexican endemic. They have a black breast and mask, and the back is a shade of dark gray. Their throat is bright yellow, and an extensive white patch on the wings are visible when resting.
- Goldman's Warbler S. c. goldmani – non-migratory endemic to the highlands of Guatemala. Similar in appearance to the Black-fronted Warbler, but the back is entirely black. They have patches of white on their yellow throats.
Appearance[]
Size and Shape[]
The Yellow-rumped Warblers is a fairly large, full-bodied bird with a large head, sturdy bill, and long, narrow tail. They measure 4.7-5.5 in (12-14 cm) in length, 0.4-0.5 oz (12-13 g) in width, and have a wingspan of 7.5-9.1 in (19-23 cm). Their average basal metabolic rate is 0.1895 W.
Coloring[]
As the name suggests, Yellow-rumped Warblers possess a yellow rump. All species share yellow flank patches and white eyerings. Breeding birds flaunt yellow crowns. Males are generally more striking than females, who are duller and may show some brown. Winter birds display similar patterning, but are duller and paler brown.
Distribution[]
Distribution map provided by the Cornell Lab of Ornithology.
Yellow-rumped Warblers frequent North America, Central America, and the Carribean. Myrtle Warblers are rare vagrants to western Europe, and have wintered in Great Britain.
Warblers spend the breeding season in mature coniferous and mixed coniferous-deciduous woodlands, preferring small openings with dense, wet, hardwood forest. They will also use spruce-tamarack bogs. In the western U.S. and in the central Appalachian mountains, they are found mostly in mountainous areas. In the Pacific Northwest and the Northeast, they occur from elevations of 12,000 feet to sea level in places where conifers are present. One notable exception to their breeding habitat is the San Juan Islands, where they nest in Pacific madrone. During fall and winter, Yellow-rumped Warblers frequent to higher elevations, finding open areas with fruiting shrubs or scattered trees. On their tropical wintering grounds they live in mangroves, thorn scrub, pine-oak-fir forests, and shade coffee plantations.
Migration[]
Yellow-rumped Warblers are short to long-distance migrants. They are one of the last warblers to leave their breeding grounds in the fall, and one of the first to return in the spring. Large waves of migrants leave the Cascades and more northerly habitats and arrive in the eastern Washington lowlands in autumn. In winter, flocks may wander in search of food sources.
Life History[]
Lifespan[]
The average lifespan in captivity is 6.9 years, with the oldest recorded being 7 years of age.
Diet[]
Yellow-rumped Warblers eat mainly insects in the summer, including 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. On migration and in winter they eat great numbers of fruits, particularly bayberry and wax myrtle. This is thanks to their unique gastrointestinal traits to allow them of assimilating 80% of wax-coated berries such as bayberries. The habit is one reason why Yellow-rumped Warblers winter so much farther north than other warbler species. Other commonly eaten fruits 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.
Feeding[]
Warblers hop from branch to branch in search of insects or berries.
Yellow-rumped Warblers flit through the canopies of coniferous trees as they forage. They cling to the bark surface to look for hidden insects more than many warblers do, but they also frequently sit on exposed branches and catch passing insects like a flycatcher does. In winter and migration, Yellow-rumped Warblers are found foraging in large flocks with their own species, always in constant motion. Yellow-rumped Warblers use a variety of foraging techniques, including gleaning prey from twigs, leaves, and occasionally tree trunks, foraging on the ground, and hawking to retrieve prey in midair. During the breeding season, males generally forage higher than females.
Behavior[]
When provoked, Yellow-rumped Warblers indicate the infraction by holding the body horizontally, fanning the tail, and raising it to form a right angle with its body.
Courtship[]
Male Myrtle Warbler fluffing feathers in courtship.
During courtship, male relentlessly follows the female, fluffs his side feathers, raises his wings and his colorful crown feathers, and hops from perch to perch, chipping. They may also make display flights in which they glide back and forth or fly slowly with exaggerated wingbeats.
Nesting[]
Males arrive on the breeding grounds a few days before the females. Monogamous pairs form shortly after the females arrive. The female builds the nest, sometimes using material the male carries to her. The nest is usually on a horizontal conifer branch or fork anywhere from 4 to 50 meters above the ground. They may build their nests far out on a main branch or tuck it close to the trunk in a secure fork of two or more branches. Occasionally, broadleaved trees and shrubs are also used.
Both parents feed the young.
The nest is a small, flat cup of twigs, grasses, moss, and rootlets, lined with plant hair and feathers that curve over the rim of the nest, partially covering the eggs. The nest takes about 10 days to build. It measures 3-4 inches across on the interior, 7.6 to 8.9 cm across on the exterior, and about 2 inches tall when finished. The female incubates 1 to 6 eggs for 12 to 13 days. The white, speckled with brown, reddish-brown, gray, or purplish gray eggs measure 0.7-0.8 in (1.7-2.1 cm) in length and 0.5-0.6 in (1.3-1.5 cm) in width. At hatching, the chicks are altricial; helpless and naked with sparse brown down. Their eyelids have dull white spots. The male feeds the female at the nest, and occasionally helps incubate. Both members of the pair feed the young, which fledge in 12-14 days.
Young can make short flights 2-3 days of leaving the nest. Once the young fledge, the female often starts a second brood, while the male continues to feed the first brood for up to two weeks.
Flight[]
A male Audbon's warbler takes flight, flashing his grey underwings.
The Yellow-rumped Warbler's flight is fast, slightly undulating, and direct with rapid wing beats. The overall appearance can be described as agile and swift, and the birds often call as they change direction.
Vocalizations[]
Song[]
In spring, male warblers sing to attract potential mates and warn off rival males.
Males sing a slow, soft, sweetly whistled warble or trill. The pitch is mostly even but may rise or fall slightly, speeding up as it ends. Songs last 1-3 seconds and consist of up to 21 individual notes.
Calls[]
Yellow-rumped Warblers have two main calls. The more common one, a sharp chek, differs between the myrtle and Audubon's races. The Myrtle's call a flat, husky note, while Audubon's are higher-pitched and relatively musical; an ascending jip. Both sexes make this call frequently, both while foraging and while flying. Yellow-rumped Warblers also make a soft psit and high, upslurred tsee in flight.
Conservation[]
The Yellow-rumped Warbler is abundant throughout its range and is probably the most abundant of all warbler species. Populations are generally stable, though they experienced a small decline from 1966 to 2015, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 130 million with 58% spending some part of the year in the U.S., 71% in Canada, and 31% wintering in Mexico. The species rates a 6 out of 20 on the Continental Concern Score and are not on the 2016 State of North America's Birds' Watch List. Myrtle Yellow-rumped Warblers are expanding their range in parts of the northeastern United States Migrating Yellow-rumped Warblers, like many migrants, are frequently killed in collisions with radio towers, buildings, and other obstructions.
Ecology[]
The Yellow-rumped Warbler has a positive impact on humans by eating potentially harmful insects.
Trivia[]
- The Yellow-rumped Warbler is the only warbler able to digest the waxes on wax-coated berries, such as bayberries and wax myrtles. The ability to use these fruits allows it to winter farther north than other warblers, sometimes as far north as Newfoundland.
- Female Yellow-rumped Warblers tend to forage lower in trees than males do.
- When Yellow-rumped Warblers forage with other warbler species, they typically assert themselves over Pine and Blackburnian warblers but ignore Palm, Magnolia, and Black-throated Green warblers.