About Zimmerius vilissimus petersi (Berlepsch, 1907)
The Guatemalan tyrannulet, Zimmerius vilissimus petersi, is 10 to 12 cm (3.9 to 4.7 in) long, and males and females have identical plumage. Adult individuals have a grayish crown and a short whitish supercilium. Their upperparts are olive green, while their wings and tail are mostly olive green with yellow edges on the wing coverts, flight feathers, and tail feathers. Their underparts are mostly off-white, with faint darker streaks on the breast, and sometimes a pale yellow wash on the belly and undertail coverts. Both sexes have a light brown or brownish black iris, a short brownish black bill, and long brownish black legs and feet. Immature birds have dark irises and more green in their crown than adults. This subspecies is distributed from the southern Mexican state of Chiapas, east across Guatemala into southern Belize, and south through Guatemala into El Salvador. It inhabits the interior and edges of evergreen forest, as well as more open forest, plantations, and fields with scattered trees and shrubs. It particularly favors areas that contain mistletoes of the family Loranthaceae. It occurs at elevations between 500 and 2,500 m (1,600 and 8,200 ft).
