Short-tailed Pygmy-Tyrant

The short-tailed pygmy tyrant is 6 to 7 cm (2.4 to 2.8 in) long and weighs about 4.2 g (0.15 oz). It is the smallest passerine on Earth. The sexes have the same plumage. Adults of the nominate subspecies have a mostly dark gray head with blackish lores, a prominent white spot above the lores, and a white eye-ring; the last two give a spectacled appearance. Their back, rump, and uppertail coverts are bright olive green. Their wings are dusky with bright olive edges on the flight feathers and tips on the coverts; the latter show as two faint wing bars. They have an extremely short, mostly black, tail. Their throat and underparts are white with a pale yellow tinge on the crissum. They have a brown to dark iris, a black bill that is unusually long for a bird its size, and pinkish legs and feet. Subspecies M. e. miserabilis has a darker and duller green back than the nominate, with a darker gray crown and nape, grayer or pale olivaceous sides on the breast, and darker legs. Juveniles of both subspecies resemble their respective adults. The short-tailed pygmy tyrant resembles the larger slate-headed tody-flycatcher (Poecilotriccus sylvia) but "is much more likely to be mistaken for a large beetle or insect, [especially] in flight, than another bird".

The short-tailed pygmy tyrant is primarily a bird of the Amazon Basin though it is found outside that area. The nominate subspecies is found on Trinidad and from the southeastern third of Colombia east through the southern half of Venezuela, the Guianas, and northern Brazil north of the Amazon and east of the upper Negro River. It is found also in the Andes of northwestern Venezuela and coastally in Carabobo and Sucre states. (The map in McMullan's Field Guide to the Birds of Colombia shows a much more extensive range in that country than do other maps.) Subspecies M. e. miserabilis is found in eastern Ecuador, eastern Peru, northern and eastern Bolivia, and Brazil south of the Amazon. The species inhabits the interior, edges, and gaps in humid forest and also nearby secondary and transitional forest in the lowlands and Andean foothills. In elevation it occurs below 500 m (1,600 ft) in Colombia, below 400 m (1,300 ft) in Ecuador, below 1,000 m (3,300 ft) in Peru, and below 950 m (3,100 ft) in Brazil. In Venezuela it occurs below 500 m (1,600 ft) north of the Orinoco River and below 900 m (3,000 ft) south of it.

The short-tailed pygmy tyrant feeds on insects. It typically forages singly or in pairs and very rarely joins mixed-species feeding flocks. It mostly forages in the forest canopy though lower at the edges and in gaps. It takes prey mostly by using short upward sallies from a perch to grab it from leaves, and also sometimes gleans it while briefly hovering after a short flight.