[2] It is found in Costa Rica, Panama, on Trinidad, in every mainland South American country except Chile and Uruguay, and as a vagrant on Bonaire and Curaçao.

Adults of the nominate subspecies have a grayish olive head with lighter cheeks, a thin whitish eyering, and a partially hidden white patch on the crown.

Their throat is gray, their breast grayish olive, and their belly and undertail coverts pale yellow.

However, the southernmost Brazilian population apparently moves north for the austral winter, though how far is not known, and the species appears to be present in Rio Grande do Norte only between May and December.

It forages singly or in pairs, usually from the upper levels of the understory and higher, and mostly by gleaning while perched, while briefly hovering, and with short sallies to take prey on the wing.

Its nest is a cup made from plant fibers, leaves, and moss lined with feathers, and typically placed in a shrub or tree up to about 4 m (15 ft) above the ground.

Clutch sizes apparently vary geographically, with up to four eggs known in Panama but a maximum of three in central Brazil.

The lesser elaenia's dawn song is a "very high, hurried, 'tju-wee tju-weederwee' " whose "wee" notes are higher than the others.

It has an extremely large range and its estimated population of at least five million mature individuals is believed to be stable.

[1] It is considered fairly common on Costa Rica's Pacific slope but uncommon in the center of the country.