Yellow-billed Babbler Turdoides affinis
Version: 2.0 — Published September 17, 2020
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A medium-sized babbler – 23 cm long and 63 g body mass – with a dull brown body, very pale-head, and yellow bill and legs. The chin, throat, and chest tend to be darker than the rest of the underparts, with the breast having distinct scaly pattern; the rest of underparts otherwise buffy-gray. Upperparts are gray to brownish-gray, with some streaking on the back and scapulars. Pale gray fringes on flight-feathers form broad gray panel that is distinctive. Sexes are similar.
Jungle Babbler (Turdoides striata) is very similar looking and the most closely related species. Yellow-billed Babblers have a pale head and dark mottling on the throat and chest, as opposed to the uniform head and crown, and lightly streaked throat and chest of the Jungle Babbler. The pale gray wing panel is also distinct for the Yellow-billed Babbler. The two species overlap across their distribution range in south India, but not in Sri Lanka, where the Jungle babbler does not occur. In south India, both species can often be found in the same patch, sometimes even occurring together (6). Yellow-billed Babblers are known to prefer slightly more open habitat than Jungle Babblers (7).
Large Gray Babbler (Turdoides malcolmi) is distinctly larger and uniform gray with dark lores. Both species overlap in southern India but not in Sri Lanka, where Large Gray Babbler does not occur. Large Gray Babbler prefers more open dry scrub habitat and cultivation in the plains compared to Yellow-billed Babbler (7).
Common Babbler (Turdoides caudata) is similar in size but clearly different in appearance. In Common Babbler, the throat and breast are white and un-streaked while the back is heavily streaked and the bill is slender and curved. The underparts are buff and plain in Common Babbler. Both species overlap in southern India but the Common Babbler does not occur in Sri Lanka. Common Babbler prefers more open dry scrub habitat in the plains, which is more similar to Large Gray Babbler in habitat preference than to Yellow-billed Babbler (7).
Rufous Babbler (Turdoides subrufa) is endemic to the high elevation areas (above 800 m) of the Western Ghats, preferring the undergrowth of evergreen forest and moist deciduous forest, but also occurring at forest edges and coffee plantations. Marginally larger than Yellow-billed Babbler, Rufous Babblers have distinctly rufous underparts, brown back, and dark lores (7).
Orange-billed Babbler (Turdoides rufescens) is it the only other Turdoides sp. occurring in Sri Lanka. It has a distinctly orange-yellow bill, rufous underparts, and brown back, which are more reminiscent of the Rufous Babbler. It prefers primary evergreen forest, but sometimes occurs in secondary logged forest and plantations (7).
Afghan Babbler (Turdoides huttoni), Slender-billed babbler (Turdoides longirostris), Spiny Babbler (Turdoides nipalensis), and Striated Babbler (Turdoides earlei) are the other Turdoides sp. in the Indian Sub-continental region, but they do not overlap the Yellow-billed Babbler in distribution, and therefore are unlikely to be confused with them.
The following descriptions are for the nominate subspecies.
Juveniles are similar to adults, but with less distinct streaks above and scales below.
No distinct formative plumage.
Definitive Basic Plumage
Both sexes look similar and have a grayish cream crown, lores, and superciliary area. The nape has shading that transitions to the pale gray mantle. Back and scapulars are brownish gray with pale gray streaks, while the rump is plain pale brownish gray. The upperwing is dull grayish brown, with pale gray fringes on flight feathers which forms a distinct broad gray wing panel. The tail has a pale gray-brown base, and is dark brown with narrow blackish-brown barring at the distal end. On the head, the ear coverts are plain pale gray brown with buff-tan tinge, while the chin, submoustachial area, throat, and breast are dull brown with broad pale gray scaling. Long whitish shaft streaks appear on the lower breast and continue onto the plain buffy-gray upper belly and flanks. The remaining underparts are pale buff gray.
All information on molt in Yellow-billed Babblers comes from Zacharias et al. (8).
Juveniles undergo a partial or complete molt starting at three months from fledging. It begins with the frontal tract or first primary.
Adult Yellow-billed Babblers undergo one molt every year (8). Body feather molting starts in March and continues until November with they highest intensity between September and October. Primaries and secondaries molt from a single and two foci, respectively, and starts in April and continues through November. There are 10 primaries and the molt starts from the first and continues in ascending order. There are nine secondaries and the molting starts from A1 and A5 or A6. The molting of tertials starts anywhere between A7-9. The upper greater primary coverts molt in close coordination with the primaries, but the secondary coverts sometimes molt ahead of the respective secondaries. The twelve rectrices start molting from the central feathers and continue outward. Alular quills molt from proximal to distal end.
Bill and Gape
Bill is fresh yellow. Gape is pinkish yellow in adults and orange yellow in young birds.
Iris and Facial Skin
Ranges from creamy white to pale blue. Greenish gray in young birds .
Legs and Feet
Legs, feet, and claws are pale yellow.
Average length of the bird is 22.9 (21-23.5) cm (n = 30; 1)
|Male (9)||Female (9)||Average and range (n = 30; 1)|
|Bill (from skull)||20-22||19-23||24 (19-24)|
Average mass is 63.3 g (n = 30; 1).