Dusky Naumann’s Thrush (Turdus eunomus)

Identification

Asian vagrant (breeds in Siberia central from eastwards). Recalls Redwing in structure, but substantially larger with stouter bill and relatively long tail. The two subspecies appear distinctly different in the field and are best considered separately.

The medium size Dusky Naumann’s Thrush adult male bird is dull dark brown above with blackish feather centers, giving the mottled appearance (with wear upperparts appear blacker). Hence, becoming blacker on the crown and ear-coverts which contrast with conspicuous white supercilium and throat, latter extending across the side of the neck to form half-collar as in Redwing.

Moreover, the feathers of rump and upper tail coverts broadly fringed rufous, and wings largely rufous-chestnut. The whitish underparts are heavily mottled and scaled blackish, forming ill-defined breast bands that contrast with cleaner throat. The underwing is almost entirely rufous.

Unlikely to be confused, but occasional variant individuals lacking rufous-chestnut in wings could perhaps be confused with female Black-throated Thrush. Adult females’ bird and 1st-years are usually duller overall, with duller rufous-buff area in wings, and are less intensely scaled and mottled than adult males. These birds are most likely to be confused with smaller Redwing.

Which is also shows paler areas on the wing, prominent pale supercilium and collar, and diffuse breast streaking forming chest band. But Redwing has rufous flanks, is browner above, has rich buff ground color to breast and buff wash to supercilium, and has darker rufous underwing (duller rufous in Dusky).

Therefore, some Dusky have rufous scaling mixed with black on underparts, especially on flanks, and others are intermediate between Dusky and Naumann’s. All kinds of apparent intermediate plumages can be seen.

Naumann’s Thrush (nominate race)! Upperparts lack the blackish mottling of Dusky, being greyish-brown overall, while underpart markings are rufous-chestnut instead of black, often being more diffuse and thus producing almost wholly rufous breast and flanks, mixed with whitish scaling in fresh plumage.

Some black speckling and scaling usually present at sides of the throat and on breast, and rufous scaling present on upperparts. The bright rufous outer tail feathers are obvious in flight, less striking on the ground (were partially obscured by browner central feathers).

The throat and supercilium are off-white, washed rusty-buff. Upperwing lacks strong rufous tones of Dusky, but the underwing is darker rufous. Adult females and 1styears average duller, but the pattern and color distinctive and not matched by any other thrush of our region.  

Although red-throated race of Dark-throated Thrush also has a bright rufous tail. Both forms feed more in open than most other Asian thrushes, perching freely on tops of bushes and trees and feeding on the ground in the manner of Fieldfare.

Sex and Age

As already discussed under the Identification section. Some adult male Dusky is duller than usual and so sexing not always straightforward. However, adult females generally have less blackish feather centers above and below, often have more distinct malar stripe and primary coverts appear duller, less strongly rufous, with less distinct, brownish (rather than blackish) tips.

Adult Naumann’s often hard to sex, but females average duller below (especially on the throat, which is often paler), tend to show more distinct malar stripe and usually have less rufous on scapulars. The juveniles of both forms are heavily pale-spotted above and dark-spotted below.

The 1^st-years maybe aged by more distinct whitish or pale buff tips to greater coverts than in adults. 1st-year male Dusky usually resembles adult males in having blacker feather centers on both upperparts and underparts, but primary coverts are closer to those of adult females (although dark tips are blacker and more distinct).

Some 1st-year female Naumann’s may be separated by obvious dark spotting on the breast (and sometimes flanks), but many inseparable from 1styear males.

Voice                                                                        

The bird simple flute calls include a harsh chattering ‘chak-chakchak’ of alarm, recalling Fieldfare, a shrill, wheezy ‘spirr’, recalling Common Starling, a loud, shrill, nasal ‘cheeh-cheeh’ and many other high-pitched calls. The whistling song, unlikely to be heard consists of several clear, descending notes followed by a faint twitter and recalls Redwing.

Taxonomy

Intermediates between Dusky and Naumann’s Thrushes are not infrequent. But as the area of hybridization appears to be quite limited Dusky Thrush is sometimes accorded full species status as T. eunomus.

Geographical Variation

Differences discussed under Identification. Race eunomus (Dusky Thrush) breeds further north than nominate race (Naumann’s Thrush). Both occur as rare vagrants, with most of northern records being of Dusky whereas less frequent Naumann’s has predominated among records from the south.

Status / Habitat

The vagrant birds found in Europe, Cyprus, and Middle East. In natural range breeds in rather open deciduous or coniferous forests and in willow scrub at the southern edge of the tundra. In winter quarters, favors groves, orchards, and open fields. 

Also Read: The Orange-Breasted Bunting / The fire-tailed myzornis