Appearance

The Russet-bellied Spinetail is one of the most distinctive members of the Synallaxis genus in terms of its plumage and tail structure, but its overall body form resembles that of other spinetails. It is the only species of Synallaxis whose range extends so far south along the west slope of the Andes. There is no geographical variation in the species’ unique plumage characteristics. The head is grey, becoming olivaceous grey along the back, with blackish lores, an indistinct ashy-grey supercilium and a prominent broken white eye-ring. The tail is dusky and graduated with the outer tail feathers becoming increasingly rufous. The rump and uppertail coverts are bright rufous, in contrast with the back colour. The wing-coverts are darker rufous. The chin is a prominent ashy grey to white blending into greyish-brown throat and upper breast that is faintly streaked. The rest of the underparts are rufous. The bill is dark grey to black sometimes with a yellowish base, and the tarsus dark grey. Both sexes are alike.

Throughout its narrow geographic range the Russet-bellied Spinetail has no overlap with any other Synallaxis species. Koepcke (1957) reports that the species occasionally associates with Leptasthenura Tit-spinetail and Cranioleuca spinetail species but this has not been observed by most recent authors (e.g. Frank and Salinas 2001).

Synallaxis zimmeri is a medium sized and very distinctive species of spinetail with a graduated tail.

Adult: The head is grey, with blackish lores and slightly paler auriculars, with an indistinct grey-white supercilium and a prominent broken white eye-ring. The grey colouration of the head blends into olivaceous grey along the back. The tail is graduated, with 10 blunt retrices. The uppertail coverts are bright rufous, in contrast with the back colour. The wing-coverts are dark rufous (almost chestnut), remiges brownish. The tail is fairly dark overall; the central tail feathers are dark fuscous, with the outer tail feathers becoming increasingly rufous. The chin is ashy grey to white and blends into a greyish-brown throat and upper breast that is faintly streaked. The rest of the underparts are rufous, and darkest on the under-tail coverts. No sexual dimorphism.

Juvenile: Similar to adult, but the bill is shorter and paler (Franke and Salinas 2001)

Not described

Iris: Black or dark grey.

Bill: Dark grey to black, sometimes mandible is grey or bright green-to-yellowish (younger birds?).

Tarsus and toes: Dark grey.

Length: 16.5-17cm

Mass: 12-14 g