Picumnus is a large genus of piculets. With a total length of 8–10 cm (3–4 in), they are among the smallest birds in the woodpecker family. All species are found in the Neotropics except the speckled piculet (Picumnus innominatus) that has a wide distribution in China, India and Southeast Asia.

Species limits in this genus are doubtful, and the rate of interbreeding is "inordinately high" (Remsen et al. 2007). As defined by Winkler and Christie (2002), it contains the 27 species listed below, all from the Neotropics except the speckled piculet, which is Asian (and sometimes placed in a monotypic genus, Vivia).

Their upperparts are brownish, greyish or olive, in some species with darker barring or white or yellowish spotting on the mantle. The underparts vary greatly among the species, ranging from all rich brown in the chestnut piculet, to whitish in the plain-breasted piculet, white with dark bars in the white-barred piculet, and pale yellowish with dark bars on the chest and dark spots and streaks on the belly in the bar-breasted piculet. They have black crowns with red, orange, or yellow marks in the male and white dots in the female, except that the male speckled piculet has brown crown marks and the female lacks white dots. Most have rather short black tails with white stripes down the edges and the center (Blume and Winkler 2003). In two species, the rufous-breasted and the chestnut piculets, the white is largely replaced by rufous.

While the individual species often are habitat specialists (as evident by a number of highly restricted species such as the rusty-necked and ochraceous piculets), members of this genus range from dry Caatinga woodland to humid Amazonian and Atlantic Forest. They are generally found in pairs or small groups. The Neotropical species fall into two broad song groups, with the first having a song consisting of a long trill, and the second a song consisting of series of two or more descending notes.

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