White-bellied Spinetail is an interesting member of the rather large genus of spinetails, Synallaxis, that is restricted to early successional habitats found on ephemeral sandbar river-islands along the Amazon River and its major tributaries, from central Brazil to eastern Ecuador, eastern Peru, and northern Bolivia; it also occurs locally east to French Guiana and eastern Amazonian Brazil. Although it has an extensive range, its distribution is quite linear being highly restricted to the riverine habitats, where it is found almost exclusively in the "earliest" successional vegetation coming up on an island (such as grass, cane, and Tessaria sp. scrub); it can be quite common in these habitats. White-bellied Spinetail overlaps in range with both Plain-crowned Spinetail (Synallaxis gujanensis) and Dark-breasted Spinetail (Synallaxis albigularis). Both White-bellied and Plain-crowned spinetails lack the bright rufous cap of most species of Synallaxis spinetails, but Plain-crowned occupies the understory of larger, older islands, and has very different vocalizations. White-bellied is told from Dark-breasted by the lack of rufous cap, and different calls. White-bellied actually does have a white lower belly, but other characters, such as habitat and call, are more useful for identifying this species. The call of White-bellied Spinetail is a distinctive gravelly growl, which is very different from the loud machine gun-like "dit---ditditdit" of Dark-breasted. Little is known about the seasonal movements of White-bellied Spinetail. During periods of high water, much of its preferred habitat can be flooded, or sometimes completely covered by water, yet there are no records of this species away from these islands.