IDENTIFICATION

VOCALISATIONS

The song is higher-pitched, pacier and more melodious than Chinese Bulbul.

Calls are also higher in pitch, though the difference is not so marked and a few are very similar to Chinese Bulbul. Relaxed birds may utter a variety of calls.

The following call was recorded from a slightly agitated bird.

More agitated birds utter a series of anxious notes.

When gathering for roost, while still at the roost early morning or when mobbing a stationary raptor, the following chatter of notes may be heard.

DISTRIBUTION AND HABITAT PREFERENCE

Red-whiskered Bulbul is the second most widespread bird species in HK in both summer and winter, with only Chinese Bulbul more widely distributed. It was recorded from 71.5% of squares in both the 1993-96 and 2016-19 breeding atlas and from 72.9% of squares in the 2001-05 and 66.2% of squares in the 2016-19 winter atlas surveys. It is generally present throughout HK, being absent only from a few of the smallest islands, and it is but patchily distributed in some wooded upland areas in the central and eastern New Territories and on Lantau, as well as in impoverished upland grassland on Castle Peak and the Castle Peak hinterland.

Red-whiskered Bulbul utilises most terrestrial habitats but is especially abundant in edge areas between woodland and more anthropogenic habitats including village areas, farmland, parks, gardens and fish ponds where it generally outnumbers Chinese Bulbul (Chan 2004). Conversely, it is relatively scarce in extensive forest and closed canopy shrubland areas such as those of the central New Territories, where densities are usually lower than those of Chinese Bulbul (Kwok and Corlett 1999, Chan 2004). However, though it is less widespread than that species, the abundance data collected in the 2016-19 atlas surveys show that in most parts of HK Red-whiskered Bulbul outnumbers Chinese Bulbul in both the breeding season and in winter. This represents a change from the view expressed by previous authors, notably Herklots (1953) and Carey et al. (2001), that Chinese Bulbul is the more abundant of the two species. Whilst it would be difficult to prove, it seems that this change might be genuine: the first breeding season atlas was not quantitative, while comparison with the 2001-05 winter atlas surveys suggests that Red-whiskered Bulbul has increased in numbers over the intervening period, perhaps especially in the northwest New Territories and around the main urban areas of HK Island and Kowloon.

This increase does not appear to have been at the expense of Chinese Bulbul, the numbers of which do not appear to have changed materially. Whilst they have slightly different habitat preferences and diets (see below) the two species often occur together at fruiting trees or other food sources and neither appears to dominate the other (they are of a similar size and weight).

The recent increase is only the most recent change in the status of Red-whiskered Bulbul in HK, and indeed in China. Swinhoe (1861) observed Red-whiskered Bulbul in Guangzhou, where he found it to be ‘very abundant’ but noted that it was not found in either HK or Macau. Similarly, unlike Chinese and Sooty-headed Bulbuls, Red-whiskered Bulbul was not listed for HK by Kershaw (1904) (contra Carey et al. (2001) and Leven and Corlett (2004)). If this omission was not an oversight, it seems that Red-whiskered Bulbul arrived in HK at some point between 1903 (the last year of Kershaw’s observations) and 1913, when Vaughan and Jones (1913) found it to be a common resident in both HK and Macau.

Whether Red-whiskered Bulbul reached HK, or indeed southeast China, naturally or through human agency is uncertain. Whilst a natural origin appears to have been assumed by previous authors including Carey et al. (2001), Leven and Corlett (2004) suggested that in view of its absence from forest in Guangdong Province, it might be alien to the region, a suggestion that perhaps receives some support from the recent establishment of (presumed) feral populations in central China (see below). However, whilst of biogeographic interest, the origin of the southeast China population of Red-whiskered Bulbul seems destined to remain a moot point and the southeast and (presumed natural) southwest China populations are (now) continuous. 

OCCURRENCE

As noted by Carey et al. (2001), there appears to be no firm evidence of migratory movements of Red-whiskered Bulbul in HK and it seems likely that the flocks in spring and autumn that formed the basis of the suggestion by Vaughan and Jones (1913) that this species is partially migratory in the region were local aggregations. Especially in autumn, Red-whiskered Bulbul typically occurs in small flocks of 20 to 30 birds, often at fruiting trees with other species, especially Chinese Bulbuls. However, larger numbers have been observed at roosts, again especially in autumn. Such roosts are found in dense long grass or reeds (when they may be over water). Counts in recent years, all of which exceed the highest count cited by Carey et al. (2001), include at least 300 leaving a roost at Sha Po on 22 September 2008, 323 leaving a reedbed roost at Shuen Wan on 7 November 2004 and (the highest count or record) 641 leaving a roost in long grass Miscanthus sp. at Lung A Pai in the Lam Tsuen Valley on 14 October 2013.

BREEDING

Red-whiskered Bulbul is double or treble-brooded and the breeding season extends from March to August. Nest construction has been noted as early as 3 March and fledged young have been seen on 25 March, whilst at the other end of the breeding season a bird has been seen incubating as late as 26 July. A small, rather neat, open cup nest is constructed from leaves and fibres and three, four, or occasionally, five eggs are laid. The eggs are pale mauve, heavily spotted and blotched with darker mauve. Vaughan and Jones (1913) considered them to be indistinguishable from those of Chinese Bulbul. Nests are typically placed quite low in trees and bushes and as befits a species that favours anthropogenic habitats, it is not unusual for nests to be placed in potted shrubs on balconies or on the roofs of village houses.

BEHAVIOUR, FORAGING & DIET

One of the most familiar HK birds, Red-whiskered Bulbul is typically encountered as small noisy parties foraging in groups of trees or shrubs, and the characteristic babble of such groups may be an almost constant background accompaniment to a walk in most parks, village and farming areas in HK as well as in shrubland and forest edges. Red-whiskered and Chinese Bulbuls are often the most abundant species at fruiting trees and are usually core members of flocks mobbing owls and other predators.

Red-whiskered Bulbul eats fruit, invertebrates and plant material (including flowers, buds and leaves) but is probably primarily a frugivore, especially during November to February when it is almost entirely frugivorous (Corlett 1998). In the coldest weather, however, it readily consumes leaves, especially those of Papaya Carica papaya trees, and these may be stripped from a tree in one or two weeks. They have also been noted in cold weather eating the leaves of Tabebuia chrysantha. The methodology used by Corlett (1998) (examination of faecal contents to find seeds) would not have detected evidence of leaf consumption, and it may be that leaves provide an important alternative food source when weather is cold and fruit availability is limited.

Leven (2000) found evidence of fruit in 98% of 162 faecal samples examined, but invertebrate remains in only 14%. In this preference for fruit over invertebrates, Red-whiskered Bulbul was markedly less insectivorous than Chinese Bulbul (where 94% of samples contained fruit and 24% invertebrate remains) and most other common insectivore-frugivores in HK forest and shrubland, both breeding species (laughingthrushes, ‘babblers’ and Swinhoe’s White-eye) and non-breeding migrants (thrushes and chats). Fruit choice appeared to be driven largely by fruiting phenology, with the most readily available and abundant species at any given time being eaten; smaller fruits, up to about 10mm diameter (the size of a Machilus spp. fruit) were swallowed whole, whilst pieces of softer larger fruit such as that of Rhodomyrtus tomentosa were also consumed. Invertebrates consumed were largely Araneida, Formicidae, Coleoptera and, perhaps surprisingly, Hymenoptera.

Whilst it is primarily frugivorous, Red-whiskered Bulbul is very attracted to the abundant nectar produced by Red Cotton Trees Bombax ceiba when this species flowers in April and May, and nectar from this and perhaps other species may be important at this time of year as the availability of fruit is typically at an annual low point (Leven 2000). In addition to natural foods, Red-whiskered Bulbul will readily consume food such as rice, bread and noodles accidentally or deliberately provided by people.

Red-whiskered Bulbul largely forages in trees and shrubs but will descend to the ground both to collect fruit, for example the fallen fruit of Chinese Banyan Ficus microcarpa, and to dismember and consume larger invertebrates. Invertebrates are gathered by gleaning and sally hunting, small groups often catching flying insects such as alate termites from an exposed perch such as a treetop or a utility wire, especially in warm still spring evenings when insect emergences take place.

RANGE & SYSTEMATICS

Red-whiskered Bulbul occurs over most of India and all continental southeast Asia. In China, the published range extends north to Lijiang in the west and Shantou in the east (Liu and Chen 2021). However it appears that it is now well established in several cities in central China, notably Chengdu, Nanjing and Shanghai (eBird 2021); these populations are presumably derived from ex-captive birds. Other extralimital feral populations are established elsewhere, notably in the USA and Australia.

There are nine races, four of which occur in China. The nominate race found in HK is endemic to southern China west to Guizhou and Guangxi Provinces.

CONSERVATION STATUS

IUCN: Least Concern. Population trend decreasing.