Adults of the nominate subspecies have a white supercilium on an otherwise blackish face with faint whitish streaks.

The rest of their crown is dull grayish brown, their back slightly browner, their rump rufescent-brown, and their uppertail coverts bright rufous.

Subspecies S. s. maculata is found from southern Loja Province in extreme southwestern Ecuador into northwestern Peru as far south as the Department of La Libertad.

It gleans its prey from moss, live and dead leaves, and small branches, usually within about 1 or 2 m (3 or 7 ft) of the ground.

[9][10] The necklaced spinetail's breeding season has not been defined, but active nests have been found in February and March.

Its nest is a ball of sticks with a side entrance and an inner chamber lined with feathers and soft seed down.

The necklaced spinetail's principal song is "a short stuttering chatter ending with several squeaky emphasized notes...trrr-tr-tr-kweet...kweet".

Pairs sing in duet, usually in the early morning and late afternoon, and usually from deep in dense vegetation though sometimes from a visible perch.

Its calls include a "long rattled series of notes...which may go up and down in pace and pitch", a "nasal upslurred weet or slightly disyllabic (as in song) kweet", and a "squeaky di'vot".