The scaled piculet is long and weighs . Adult males of the
nominate subspecies P. s. squamulatus have a black cap with red feather tips on the forehead and white ones on the rest of it. Their face is mostly brown with black tips on some feathers and a whitish line behind the eye. Their upperparts are olive brown with a scaly appearance due to narrow black borders on the feathers. Their flight feathers are brown with yellowish edges on the
secondaries and
tertials. Their tail is brownish black; the innermost pair of feathers have mostly white inner webs and the outer two pairs have a white area near the tip. Their chin and throat feathers are white with narrow gray-brown tips. The rest of their underparts are whitish with scaly markings similar to those of the upperparts. Adult females are identical but for white spots on their entire crown. Juveniles are darker above than adults and the scaly pattern on their underparts is more diffuse. Subspecies
P. s. roehli often has yellow or orange spots on the forehead instead of red ones, brighter upperparts than the nominate, a brownish yellow tinge to the belly, and narrower markings on the underparts.
P. s. lovejoyis forehead spots are always yellow and its upperparts are grayer than the nominate's.
P. s. obsoletus has a yellow-green tinge to the upperparts and has yellowish white underparts with paler and finer "scale" markings and dark streaks in the feather centers.
P. s. apurensis appears whiter than the nominate on its underparts, and the scaly marks are narrow and indistinct. The scaled piculet makes a "high-pitched squeaky 'chi-chi-ch'e'e'chi', becoming trill-like at [the] end." ==Distribution and habitat==