Chivi Vireo

Identification

The species looks similar to the related red-eyed vireo and yellow-green vireo. It is 12–14 cm (4.7–5.5 in) in length, with the mass and length of the bill and wings varying in different subspecies.<p>Hatchlings are born almost naked with yellow skin and sparse down. Juveniles have brownish or tawny (depending on subspecies) upperparts, with the greater and median coverts having brownish-green tips, and the head showing a less contrasting pattern than adults. The mouth lining is paler than adults up until 6 months of age. They may also show molt contrast on their wings.<p>Adult vireos are very similar, except in the subspecies diversus, where the female is smaller than the male. The crown is medium gray with thin but well defined gray borders, with a whitish supercilium extending above the ear coverts. The lores are a dull gray, and the nape, along with the side of the neck and the rest of the upperparts being a dull olive green. The area below the eyes is off-white in color. The wing coverts are dull gray brown, edged with olive green. The rectrices are green-gray in color, and have bright green edges. The undertail is very pale. The throat, breast, and belly are off-white or grayish-white in color, with a greenish tinge to the flank and sides of the breast. The upper mandible of the beak varies in color from black to blackish brown or a dusky gray, with the mandible being pale to blue-gray in color with a dark tip and paler base. The iris is brown in color, although it varies in shade from pale brown to reddish brown. The legs are pale brown to pale gray in color.<p>The calls of the species are typical of most of Vireo, but it has a very simple repertoire with only one song and one vocalization. Its song is a pattern of brief musical sound with pauses in between. The song of the South American subspecies is usually "chew-lee chew-lew wee-chee chew leee", while the song of griseobarbatus is a "tche-wit ... tche-wut" repeated constantly during the breeding season. solimoensis is said to have a shorter and more repetitive song, while the song of the migratory populations in the south of the range is said to more complex than that of resident subspecies. In Bolivia, the song is said to be composed of "chee’wee? chee’wip" repeated. The principal call is a raspy "zheer", or a more nasal "jeeyr", with the warning call being "gweh" or "greh".

Taxonomy

The chivi vireo was described by the French ornithologist Louis Pierre Vieillot in 1817 and given the binomial name Sylvia chivi. The specific epithet is an onomatopoeia for its song, which Vieillot rendered as "chivi-chivi". Vieillot based his description on that for the "Gaviero" by the Spaniard Félix de Azara that had been published in 1802. Ornithologists previously treated the chivi vireo as a subspecies of the red-eyed vireo (Vireo olivaceus), but unlike the red-eyed vireo that migrates to North America, the chivi vireo remains in South America to breed and does not migrate. Based on a molecular phylogenetic study published in 2017 that found significant genetic differences and little introgression, the chivi vireo was promoted to species status.<p>There are 9 subspecies of the chivi vireo:

Scientific name

Vireo chivi

Authority

(Vieillot, 1817)

Order

Passeriformes

Family

Vireonidae

Genus

Vireo

Range and habitat

This bird is very widespread across most of northern, eastern, and central South America, with the exception of southern Chile and southern Argentina. Resident populations of the chivi vireo occur across northeastern Colombia, into Venezuela and the entirety of the Guianas into eastern Brazil. They also occur alongside many rivers in Amazonia, continuing into parts of Peru, Bolivia and Ecuador, with some resident populations inhabiting western Colombia. More migratory populations are found in south and southeastern Brazil, Paraguay, Bolivia, and Uruguay, along with the northern areas of Argentina. In the non-breeding season these populations travel north as far as Venezuela, eastern Colombia, eastern Ecuador, and eastern Peru.<p>It inhabits the canopy and subcanopy of dry to wet forests, along with borders, light woodland, restinga, gallery forest in the cerrado, dense scrub, small tree groves, and secondary growth with tall trees. It inhabits semi-deciduous, várzea and secondary forests in Peru, ascending into montane valleys in the south. In central Amazonian Brazil, the bird is not common in mature forests, with these habitats being inhabited by migrant red-eyed vireos. It has been recorded up to an elevation of 1,900 m (6,200 ft) in Bolivia and 2,600 m (8,500 ft) in Peru, but is usually only found up to an elevation of 1,500 m (4,900 ft) in Colombia and Brazil, and up to an elevation of 1,300 m (4,300 ft) in Ecuador. It can also inhabit highly disturbed and modified habitats as long as tall trees are present.

Migration

Resident species

Conservation

Population trend

stable