The chivi vireo (Vireo chivi) is a small South American songbird in the family Vireonidae. It was formerly considered a subspecies of the red-eyed vireo. It is usually green to yellow-green in color with off-white underparts, and a gray crown. It has a whitish supercilium extending over its ear coverts, and its lores are dull gray in color. The chivi vireo has nine subspecies. It is found throughout most of northern, eastern and central South America, only being absent from southern Chile and southern Argentina. It inhabits multiple types of habitat across its range, and appears to adjust well to slightly disturbed habitat. The chivi vireo is mainly resident, but at least two of the subspecies inhabiting the south of its range are known to be migratory.
The chivi vireo mates from May to June or October to January, depending on the region and subspecies. It makes cup nests and lay eggs in clutches of 2–4 which are incubated by the female, taking 10–16 days to hatch. Nestlings take 10–13 days to fully develop. The majority of the bird's diet is composed of arthropods, although some subspecies eat fruit and some are also thought to be nectarivorous.
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.
Subspecies
There are 9 subspecies of the chivi vireo:
Description
left|thumb|A chivi vireo in [[São Paulo (state)|Sao Paulo, Brazil]]
The species looks similar to the related red-eyed vireo and yellow-green vireo. It is in length, with the mass and length of the bill and wings varying in different subspecies.
Ecology and behavior
The species is largely resident throughout its range, but in the south of its range, the subspecies chivi and diversus are known to be migratory. There are also some subspecies that are likely to undertake short migrations.