Appearance

Synallaxis spinetails are small, slender furnariids with long, strongly graduated tails and with short, rounded wings. Spix's Spinetail is a typical Synallaxis: it is primarily dark olive-brown above and gray below, with contrasting bright rufous crown and wing coverts, and a black throat.

Spix's Spinetail is similar to, and overlaps geographically with, several other species of Synallaxis. The species that are most likely to be confused with Spix's are Sooty-fronted Spinetail (Synallaxis frontalis), Pale-breasted Spinetail (Synallaxis albescens), and Cinereous-breasted Spinetail (Synallaxis hypospodia).

Sooty-fronted Spinetail has a rufous tail (brown in Spix's) and very different vocalizations.

Pale-breasted Spinetail has a very pale (nearly white) belly. It also has a dark forecrown, unlike S. spixi, and its song is markedly different (Ridgley and Tudor 1994)

Cinereous-breasted Spinetail has a stouter bill than Spix's Spinetail, and has a brownish gray forecrown; the entire crown of Spix's is rufous. It also has a shorter, sootier, and less pointed tail than Spix's Spinetail. Cinereous-breasted Spinetail occurs in more open habitats in central South America, and so there is little geographic overlap between these two species (Ridgley and Tudor 1994).

Other Synallaxis spinetails of southeastern Brazil include Rufous-capped Spinetail (Synallaxis ruficapilla), which has a prominent buff streak along the lower margin of the rufous crown, and Gray-bellied Spinetail (Synallaxis cinerascens), which has a brown (not rufous) crown.

The following description is based on Remsen (2003):

Adult: Sexes similar. Face grayish brown, with narrow paler supercilium. Crown rufous. Upperparts (back and rump) dark brown. Lesser wing coverts rufous; median and greater wing coverts dark brown, feathers with broad rufous margins. Remiges dark brown. Tail graduated; central rectrices sharply pointed and disintegrated towards the tip. Rectrices dark brown. Throat grayish white; lower throat black, feathers edged with grayish. Breast brownish gray, belly paler; flanks and undertail coverts browner.

Juvenile: Lacks the rufous crown of the adult. Upperparts slightly darker than adult, the throat patch is less distinct, and the underparts are mostly ochraceous brown.

No information.

Iris: reddish brown to pale orange

Bill: maxilla black; mandible gray (adults) or pinkish ("young individuals")

Tarsus: gray to greenish gray

Bart parts color data from Belton (1984).

Total length: 16 cm (Ridgley and Tudor 1994), 16-17 cm (Remsen 2003)

Mass: Three males, 12-13 g; one female, 13 g (Belton 1984). One individual (sex undetermined), 15 g (de Faria and de Paula 2008).