IDENTIFICATION

VOCALISATIONS

The song is a rather jaunty short series of somewhat piercing notes. Flight calls can be heard at the end of this recording.

Calls include single or pairs of notes.

The calls of parties of birds are harsher than those of other bulbuls in HK.

DISTRIBUTION & HABITAT PREFERENCE

Sooty-headed Bulbul favours dry, lightly wooded grassy hillsides, open canopy shrubland and farmland, including areas of former farmland so long as invading trees and shrubs remain scattered. Whilst it appears to avoid large semi-natural wetlands, it does occur in small numbers in some fish pond areas such as at San Tin and Hoo Hok Wai. Of the three bulbuls regularly found in open country in HK (the others being Chinese Bulbul and Red-whiskered Bulbul), it is the least tolerant of developed areas, so whilst it is found in proximity to more isolated squatter houses in such places as Mong Tseng and Long Valley, it is relatively scarce in former agricultural areas where village development is intensive such as around Kam Tin and in Lam Tsuen Valley.

The earliest chroniclers of HK’s avifauna all appeared to encounter Sooty-headed Bulbul frequently, but suggested that Chinese Bulbul was commoner, even then. Thus, Swinhoe (1861) referred to his often meeting ‘small parties in the hills’ whereas he considered Chinese Bulbul to be abundant; similarly, Kershaw (1904) described it as being ‘commoner in the hills but found all over the district’, but noted that Chinese Bulbul was ‘certainly the commonest Bulbul’.  Likewise,  Vaughan and Jones (1913) referred to often seeing ‘large flocks’ of Sooty-headed Bulbuls in spring and autumn, but stated that Chinese Bulbul was the commonest of the three breeding bulbuls (Red-whiskered Bulbul also being present by that time).

The earliest direct comparison of numbers of the three species was provided by Hutson (1930) who described Sooty-headed Bulbul as ‘perhaps the least common of the three’. Herklots (1934) described it as ‘abundant’; however, this is perhaps a simplification as in the very same issue of The Hong Kong Naturalist, Pereira (1934) stated that it was ‘Almost always found in pairs or in groups of three or four these birds are scarce.’ Furthermore, he then went on to state ‘owing to their scarcity, perhaps, these birds do not attract the attention of trappers’ (unlike the other two species). Herklots (1953) described Sooty-headed Bulbul as common, but qualified this by stating that it was the least abundant of the common bulbuls. However, Dove and Goodhart (1955) suggested that both Sooty-headed and Chinese Bulbuls were more common than Red-whiskered in the New Territories; there must have been an abundance of habitats favoured by Sooty-headed Bulbul in the New Territories at that time.

Sooty-headed Bulbul was still described by Chalmers (1986) as common and widespread; however Carey et al. (2001) considered it to be far more localised than Red-whiskered and Chinese Bulbuls and ascribed the reduction in range to the loss of agricultural areas and edge habitats. Sooty-headed Bulbul was still found in 30.9% of squares in the first breeding atlas survey of 1993-96 but in only 17.6% of squares in the first winter survey suggesting a further decline, though there were methodological differences between the two surveys.

The second atlas surveys of 2016-19 charted a further significant decline, with Sooty-headed Bulbul recorded in only 10.5% of squares in the breeding season survey and 7.9% in winter. In all these surveys the strongholds were in the northwest, northeast and eastern New Territories, and on Lantau and Lamma; however, the distribution is now very patchy almost everywhere with only south Lamma having a block of contiguous squares with more than a handful of individuals recorded during the breeding season.

Part of reason for the decline is no doubt the loss in farmland and edge habitat described by Carey et al. (2001); however, in much of the central and eastern New Territories and perhaps on Lantau it seems likely that the development of closed canopy woodland and shrubland on what was formerly grassland with patches of trees and shrubs or grassland with scattered trees must also be a factor. Furthermore, as these habitat changes seem almost certain to continue, it appears inevitable that Sooty-headed Bulbul is destined to become a rather rare and very localised species in HK.

OCCURRENCE

Vaughan and Jones (1913) considered that Sooty-headed Bulbul was partly migratory, occurring in large flocks in spring and autumn. Whilst there is no further evidence of its being a true migrant in HK, it is undoubtedly somewhat nomadic: records of single birds at Kai Tak on 12 September and HK Stadium on 7 October and up to four in the West Kowloon Cultural District on 24 October, all in 2020, are highly suggestive of dispersal after the breeding season.

BREEDING

Herklots (1953) described breeding as beginning in March with the main season being from April to June, sometimes extending into July. In recent years the earliest date upon which nest-building has been observed was 21 April 2005 at Kam Tin and the earliest date when fledged juveniles have been seen  was 19 May 2018 at Sha Lo Tung, whilst a pair seen with three recently-fledged young in the Lam Tsuen Valley on 9 October 2017 appears to be particularly late.

Nests were described by Vaughan and Jones (1913) as being flimsier than those of its congeners and often placed quite high in a pine tree (Pinus massoniana at that time), with a clutch of two to six eggs, usually three or four, similar in appearance to those of Chinese and Red-whiskered Bulbuls.

BEHAVIOUR, FORAGING & DIET

As befits its preference for more open habitats, Sooty-headed Bulbul is more often seen perched in the open on large trees, wires or utility poles than its congeners in HK. It is usually found as pairs or small parties; such parties often draw attention to themselves by their rather fluting calls given as birds are flying to a new perch. Parties are quite fast-moving and wide-ranging, flying for considerable distances. Conversely, single birds or pairs often remain on a vantage point such as a utility pole or the top of a dead tree for some time.

In keeping with its decline in recent years, Sooty-headed Bulbul now rarely occurs in flocks, and is usually recorded as pairs or in parties of up to five or six individuals. Even site counts of more than ten or 15 birds are now unusual, though there were regular counts of up to 40 birds in the Ho Sheung Heung area in the period from 2013 to 2018, a time when regular systematic counts were being undertaken at this site. 

Diet and foraging behaviour of Sooty-headed Bulbul has not been studied in any detail in HK, though one of the earliest observations of the diet of any bird species in the territory is a reference to flocks of this species feeding on the fruits of Chinese Tallow Tree Sapium sebiferum by Swinhoe (1861). Vaughan and Jones (1913) noted that its diet consisted of fruit and insects and a limited sample by Corlett (1998), in which he found fruit in 100% and insects in 36% of 11 faecal samples examined, suggests that like its congeners in HK this species is largely frugivorous but supplements its diet with invertebrates.

RANGE & SYSTEMATICS

Native range extends from southern China southwards to cover most of continental southeast Asia south to the Thai-Malay peninsula, together with Java and Bali; but it has been introduced widely in the Indonesian archipelago. In China it occurs from west Yunnan east to Fujian and north to northern Jiangxi and south Zhejiang (Liu and Chen 2021).

There are nine races, three of which occur in China: P .a. latouchi occurs in southwest China as far east as Guizhou, P. a. ressurectus is found in Guangxi and west Guangdong, whilst P. a. chrysorrhoides occurs from east Guangdong including HK east to Jiangxi, Fujian and south Zhejiang (Cheng 1987, Liu and Chen 2021).

CONSERVATION STATUS

IUCN: Least Concern. Population trend decreasing.