Yellow-green vireo
The yellow-green vireo is a small American passerine bird. It is migratory breeding from Mexico to Panama and wintering in the northern and eastern Andes and the western Amazon Basin.
Taxonomy
The yellow-green vireo was formally described by the American ornithologist John Cassin in 1851 under the binomial name Vireosylvia flavoviridis. The specific epithet combines the Latin flavus meaning "yellow" and viridis meaning "green". The type locality is San Juan de Nicaragua. The yellow-green vireo is now placed in the genus Vireo that was introduced in 1808 by the French ornithologist Louis Pierre Vieillot.Four subspecies are recognised:V. f. hypoleucus Van Rossem & Hachisuka, 1937 – northwest Mexico V. f. flavoviridis – central north, northeast Mexico to PanamaV. f. forreri Madarász, G, 1885 – Islas Marías V. f. insulanus Bangs, 1902 – Pearl Islands
Description
The adult yellow-green vireo is 14–14.7 cm in length and weighs 18.5 g. It has olive-green upperparts and a dusky-edged gray crown. There is a dark line from the bill to the red-brown eyes, and a white supercilium. The underparts are white with yellow breast sides and flanks. Young birds are duller with brown eyes, a brown tint to the back, and less yellow on the underparts. The adult yellow-green vireo differs from the red-eyed vireo in its much yellower underparts, lack of a black border to the duller gray crown, yellower upperparts and different eye color.Some individuals are difficult to separate, even in the hand, from the similar red-eyed vireo, with which it is sometimes considered conspecific. Its exact status as a passage bird in countries such as Venezuela is therefore uncertain.
The yellow-green vireo has a nasal call, and the song is a repetitive veree veer viree, fee'er vireo viree, shorter and faster than that of the red-eyed vireo. This species rarely sings on its wintering grounds.