Gray-bellied Spinetail

The grey-bellied spinetail is 13.5 to 15 cm (5.3 to 5.9 in) long and weighs 10 to 14 g (0.35 to 0.49 oz). The sexes have the same plumage. Adults have blackish lores and a faint gray line behind the eye on an otherwise gray-brown face. Their forehead is dark grayish brown, their crown dark brownish olive, and their back, rump, and uppertail coverts are richer brown. Their wings are mostly rich reddish chestnut. Their tail is dark chestnut; the tips of the feathers have no barbs giving a spiny appearance. Their chin is whitish, their upper throat mottled black and pale gray, and their lower throat black. Their underparts are mostly brownish gray with a paler and grayer center to the belly and browner flanks and undertail coverts. Their iris is reddish brown, their bill black (sometimes with a gray base to the mandible), and their legs and feet greenish gray. Juveniles have a less distinct throat patch than adults and slightly paler underparts with some mottling.

The grey-bellied spinetail is found from the Brazilian states of Goiás, Minas Gerais, and Espírito Santo south through eastern Paraguay and northeastern Argentina's Misiones and Corrientes provinces into northern Uruguay. It inhabits the interior of dense lowland and montane evergreen forest and mature secondary forest; it shuns the forest edges. In elevation it is found from near sea level to 1,150 m (3,800 ft).

The grey-bellied spinetail feeds on arthropods. It usually forages in pairs, on the ground and in the understorey up to about 2 m (7 ft) above the ground. It gleans its prey from leaf litter and the low vegetation.