The Sombre Tit (Parus lugubris) is about 14 cm long. The bird resembles the southeastern races of Marsh Tit, but it is considerably larger (almost Great Tit-sized), with a pale panel on the closed wing (formed by the pale edgings to the secondaries). Sombre Tit is a much more extensive dark bib, with a very stout beak, and a longer tail. It differs from southeastern forms of Willow Tit in the same way (but both species have pale wing panels).
Sombre Tit has a more extensive dark cap than either species, and this, combined with a more extensive dark bib, has the effect of greatly narrowing the white ‘cheeks’ (which broaden only gradually behind the bill). It does not overlap in range with Siberian Tit, from which it differs in the stouter bill, greyer mantle, and darker (dark brown or blackish as opposed to dusty-brown) crown, and, compared to Siberian Tit in fresh plumage, lack of rufous on flanks.
The juvenile bird is duller and dingier, with less contrast between the crown and mantle and between the bib and breast. Sombre Tit call is a distinctive, harsh churring ‘zi-zi-zi-zichrrrr’, the churr sometimes ending ‘chrrrr-r-r-r’. The songs of Sombre Tit are a piping, buzzy, loud ‘be-zoo-be-zoo-bezoo …’ and a rising and falling ‘doodle-lu-doodle-ludoodle- lu.’. Race hyrcanus of the Caspian coast has a distinctly different song; a clear ‘tiu’ given 3–5 times that recalls Willow Tit.
The form hyrcanus of eastern Azerbaijan (and Northern Iran) is sometimes treated as a full species under the name Caspian Tit or Hyrcanian Tit. There is a slight geographical variation and three races (anatoliae illustrated). The nominate race of Balkans has a dark sooty brown crown and bib, while the race anatoliae of Asia Minor and the Levant has these areas dull black and the mantle somewhat greyer-brown.
Moreover, the race hyrcanus of the Caspian fringe of eastern Azerbaijan is darker both above and below than other races, with a dark brown crown and bib (less sooty than in the nominate race) and a powerfully rusty-buff tinge to the underparts. It excavates its own nest hole (not usually seen in other races) and has a different song (see Voice). The bird is fairly common. Sombre Tit is found in open deciduous or mixed woodland and taller scrub, mainly in hilly, rocky country.