The Grey-bellied Spinetail is described in reference data as a forest bird of dense understory that eats invertebrates. A 1997 specimen study recorded streaking on the breast of a bird considered juvenile.
The specimen considered juvenile had greyish-white breast feathers with light-brown tips and pale shafts, forming a streaked pattern. Its flanks were light brown and the center of the belly buff-white.
Reference data describe it as a diurnal, terrestrial bird of dense forest understory that feeds mainly on invertebrates.
An extinction-risk assessment has not been added yet.