Yellow-throated Vireo (Vireo flavifrons)

Distribution

Breeding: Range extends from the eastern border of the Great Plains to the Atlantic Ocean, from as far north as southern Canada to the Gulf Coast, including central Texas. Particularly high abundances occur in the heavily forested Cumberland Plateau and Blue Ridge Mountains, specifically West Virginia and Virginia.

Winter: Mainly in Central America, but range extends from southern Florida and southern Texas (rare), south through central Mexico to northern South America (the mountains of Colombia, northern and western Venezuela), occasionally the Caribbean islands of Trinidad, Tobago, Cuba and the Bahamas.

Breeding habitat
Inhabits mature woods of open deciduous forest, riparian woodland, tall floodplain forest, or lowland swamp forest. Occurs less frequently in medium-aged forests or pioneer stands, mixed forest; found occasionally in orchards, groves, roadside trees. Generally requires a high, partially open canopy, also prefers woods with an intermediate tree density or basal area. Apparently has a relatively low tolerance to forest fragmentation, though this may depend on forest quality and proximity to other forested areas.

Conservation status
This vireo is of moderate conservation importance, because of its relatively small breeding Distribution, its low density throughout its range, its dependence on mature deciduous forests, and its restricted winter Distribution in tropical forests of Middle America. Populations are stable or increasing in many areas, but declines are evident in the southern Appalachians and northern New England. Understanding this species’ tolerance of forest fragmentation and change to forest structure due to silvicultural practices will be important for sustaining future populations.

Description
Male: Large-headed with a heavy bill and short tail. Male has a brilliant yellow throat, breast, and yellow “spectacles.” Its belly and two wing bars are white. The upper parts are olive-green with a contrasting gray rump.

Female: The female is similar to the male, but slightly paler.

Juvenile: Fledglings are similar to adults, but paler.

Vocalizations
Songs: Primary song is only given by males and consists of a variable series of discrete phrases separated by pauses, ahweeo, eeyay, ayo, away, oweeah, eeoway. Each phrase is short, relatively low pitched, and buzzy or harsh in quality. Often sings from the nest and is difficult to locate.

Calls: Scolding calls are harsh calls with syllables of unstructured sound, described as a repeated series of chi-chi-chi or cha-cha-cha. Contact calls audible only at close range; of short duration and pure tone; may be described as quick oui or wit sounds. A trill is formed of series of 4–14 repeated syllables, rising slightly in pitch in middle and slowing slightly toward end.

Foraging strategy
A slow, methodical forager in tree canopy or mid-story, most active early-midmorning and late afternoon–evening. Typically searches nearby substrates from one location before hopping or making short flight to new location. Upon observing prey, will hop or fly up to 6 feet (2 meters) to within striking distance, indicating that it makes visual search for prey over relatively large distances.

Diet
Consumes wide variety of arthropods, the most important are larvae and adults of butterflies and moths, stinkbugs, assassin bugs ,scale insects, leafhoppers, a wide variety of beetles, flies, bees and wasps. May take fruits and seeds in late summer, fall, and winter.

Behavior and displays
• Typically moves slowly and deliberately through vegetation.

• Flight is direct, and usually only short distances from tree to tree or branch to branch after searching about for a short interval from stationary position.

• Hops only short distances along branches to secure food, then wipes bill after feeding activity.

• The male occasionally sings at all hours throughout the summer and frequently sings on the nest.

Courtship
• The male searches for nest sites and may make barest beginnings of nest, which are used as display sites when female arrives.

• Male uses primary song and calling sequence until female comes near, then switches to precopulatory-like displays and/or ritualized “nest building” display: the male stands over the nest site, head lowered but no nest material in beak, moving head in a way that only vaguely resembles actual nest-building.

• The male also performs a “fluffing” display: following each flight, male pauses to fluff his head and body feathers slightly, and he maintains that fluff as the pair forages.

Nesting

Nest Site: Selected by male (see “Courtship” above), typically in the upper crown of trees, most often near center, but occasionally out to periphery. Often suspended between forks of slender branches, usually those growing laterally from a larger upright limb, and placed within the tree canopy.

Height: Typically 25–45 feet (8–13 meters) from the ground, ranges from 3–80 feet (1–24 meters).

Nest: The nest is a well-made deep cup of grasses and strips of bark, woven together with spider silk and plant down and lined with fine grasses. The rim is incurved, the outside decorated with moss and lichens. Male does most of the building on the first day, but his role declines thereafter.

Eggs: 3–5 (usually 3–4) white to cream-white eggs are lightly spotted with shades of brown, mostly at the larger end.

Incubation period: 14–15 days, male and female incubate.

Nestling period: Both parents share in feeding and brooding of young, which depart nest at 14–15 days.

Fledgling period: Both parents tend to the fledglings, which are dependent for about four weeks, but remain with parents until August. Parents feed any of their young for a few days, but soon brood is split, with each parent feeding half. Parents separate within 1 week of fledging, sometimes reuniting for brief periods at later dates.

Broods: No information.

Cowbird Parasitism: Commonly parasitized by the Brown-headed Cowbird, with as many as 50% of nests affected. Known to bury cowbird egg in nest bottom, or to desert nest, but typically accepts cowbird eggs.

Notes
• Thought to be entirely monogamous. Pairing is rapid, and involves courtship rather than aggressive behavior.