The tropical gnatcatcher (Polioptila plumbea) is a small active insectivorous songbird, which is a resident species throughout a large part of northern South America.

The tropical gnatcatcher was formally described in 1788 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae.

[4] Gmelin based his account on the "Plumbeous tody" that had been described in 1782 by the English ornithologist John Latham in his book A General Synopsis of Birds.

[12] In dense humid forest, it is typically found at canopy height, but it is commonly seen at lower levels in more open habitats.

The tropical gnatcatcher gleans spiders and their eggs, beetles, caterpillars and other insects from outer twigs and foliage.

[11] The nest is a small cup like that of a hummingbird, constructed from vegetable fibres 6.5 to 28 ft (2.0–8.5 m) high on a tree branch.

Even omnivorous mammals as small as the common marmoset (Callithrix jacchus) will eagerly plunder tropical gnatcatcher nests in the undergrowth – perhaps more often during the dry season when fruits are scarce – despite the birds' attempts to defend their offspring.