Hairy-backed Bulbul Tricholestes criniger Scientific name definitions

16–17 cm; 12–21 g. Small, unassuming, relatively quiet bulbul, olive above, yellowish below , with slightly rounded tail, strong rictal bristles, small and weak legs and feet. Has distinctive pale yellowish lores and broad area surrounding eye; ear-coverts pale dull yellow, longest feathers becoming brownish-olive at tips; feathering at base of lower mandible and under ear-coverts mixed with greyish-white and pale yellow, sometimes more distinctly greyish; cap and neck dark rufescent olive-brown, mantle to rump olive-brown, hair-like filoplumes (up to 50 mm long) extend from nape and mantle over back (rarely visible in field); uppertail-coverts olive-rufous, clearly demarcated; upperwings olive-rufous, especially rufescent on tertials, inner secondaries and outer margin of primaries; tail bright rufous-brown, tips of lateral rectrices creamy white (showing as distinct pale tips from below); chin and throat creamy white (greyish feather bases showing through faintly), merging into yellow of mid-breast; breast side pale grey, mottled dirty greyish-olive, or vague mottling across whole breast; upper flanks olive, lower flanks and belly to undertail-coverts yellow; iris dark brown or pale umber; bill light blue-grey, culmen ridge and tip of upper mandible black or horn-brown (difference possibly age-related); legs pale greenish-brown or fleshy brown, claws horn-brown. Sexes alike, female on average smaller than male than male. Juvenile has iris grey to grey-brown, legs, feet and claws pale fleshy pink. Race sericeus is larger than nominate, with duller yellow undertail-coverts; viridis is similar, but brighter on upperparts.

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Evergreen forests, either mature or regenerated back to a more or less closed-canopy condition; also peatswamp-forest and well-structured secondary forest, sometimes where bamboo dominates. From lowlands to 1000 m.

Resident. Long-term mist-netting in Selangor and Negeri Sembilan (Peninsular Malaysia) revealed altitudinal difference in rates of retrapping of marked individuals (24% in slope forests; 40–46% in lowland forests), implying higher density/proportion of sedentary individuals in lowlands. At Pasoh (Peninsular Malaysia), this was one of few species showing no significant difference in totals handled and retrapping rates between equivalent-sized (15–17 ha) plots of mature versus 20-year-old regenerating forest, but during breeding seasons almost twice as many individuals made repeated to regular use of regenerating plot. Repeated recapture within and between breeding seasons implies faithfulness to fixed activity space, suggesting that this is defended as a territory (but active territoriality not confirmed). Some local movements occur: in Selangor (Peninsular Malaysia), two ringed birds moved 3–5 km between captures, one of them in the space of 24 hours.

A generalist, feeding on fruit and arthropods. Animal items include caterpillars, beetles (Coleoptera), small orthopterans and mantids; apparently takes greater amount of insects than do most bulbuls. At Kerau, in Peninsular Malaysia, small parties visited five of 25 Ficus species studied, taking mainly insects attracted to the crop but also some of the fruit (in mean small-diameter range 5·4–11·6 mm). In Borneo, seen to eat berries of Macaranga and Trema orientalis. Usually encountered in lower storey or middle storey of forest, sometimes singly, more often as pairs; occasionally a small (potentially family-sized) group, with no record of more than five individuals together. Frequently joins mixed-species foraging flocks; in one study at Gombak (Peninsular Malaysia), more than half (68%) of all individuals observed were attending such flocks. Generally hunts more like a babbler (Timaliidae) than a bulbul, actively inspecting foliage and branches for arthropods. Takes small caterpillars and arthropods from foliage; flying insects caught on the wing during agile sallies. Never descends to ground. At Kerau, most fruit was cropped from perches, some in fly-past snatches; foragers showed morning and evening peaks of activity. Seems more than usually inquisitive; often approaches or follows human observers, sometimes mobbing them.

Presumed song a series of scratchy, chattering, warbled phrases interspersed with quavering “whirrrh”; in Peninsular Malaysia, same song described as a quiet, stuttering little phrase, “tutti tulip tikker tu”. Also utters long, fairly high-pitched, soft, husky, rising whistle, “whiiiii” or “chui-i”, repeated at fairly long intervals; sharp, chattering scolds, including “pree-chu, preeu-chu” and “pree-chuchu”, given by flock when mobbing human observer.

Season Feb–Aug. No other information.

Not globally threatened. Generally common. Occurs in a range of mature forest types, and able to withstand fairly drastic fragmentation of habitat. This resilience, and the species’ use of submontane slopes, suggest no immediate threat to its survival. Ongoing catastrophic clearance of lowland Sundaic forests, however, implies that overall numbers have declined dramatically, and this situation requires monitoring. Occurs in a range of protected areas, including Taman Negara National Park, in Peninsular Malaysia. An apparently isolated population at N limit of its range falls within Kaeng Krachan National Park, in Thailand.