Juveniles have whiter underparts than adults, with no black on their throat and tawny rather than rufous wings.

[8][9][10][11] The white-bellied spinetail is found along rivers in the western Amazon Basin of extreme southeastern Colombia, eastern Ecuador, northeastern and east-central Peru, northern Bolivia, southern French Guiana, and western Brazil.

[3] Major rivers in addition to the upper Amazon itself are the Napo, Pastaza, Ucayali, Madre de Díos, Jurua, and Tocantins.

[8] The white-bellied spinetail inhabits early successional growth on river islands, where it favors grassy areas with scattered bushes and small trees.

It typically forages singly or in pairs, gleaning prey from grasses, small branches, and foliage within about 2 m (7 ft) of the ground.

The white-bellied spinetail's song is "a strange, low-pitched, and nasal churring, ch-r-r-r-r-r-r-r-r"[10] that is also described as "a harsh, grating chatter: djr djr-djr'djr'djr'djr'djr'djr'djr'djr'djr-djr"[12].

In the longer term, White-bellied Spinetail potentially is vulnerable to widespread habitat loss, as might occur through perturbations of the Amazonian hydrological regime stemming from widespread deforestation, dam construction, or global climate change.