IDENTIFICATION

VOCALISATIONS

A highly vocal species, especially males, though the repertoire is not extensive. The song, which Caldwell and Caldwell (1931) described as ‘weird and monotonous’, is a series of ‘pwit’ notes, often interspersed or alternated with short trills; individually, these are also given as call notes. Recorded in song from mid-October to mid-April, though as it can be easily overlooked, this is likely to be a minimum period.

The most common calls are probably the notes incorporated into the song. Also, utters a longer, modulated and excited trill that may reach a crescendo and a ‘pit’ or ‘pwit’ note that may be repeated in a short series or for long intervals in modulated phrases.

DISTRIBUTION AND HABITAT PREFERENCE

Fork-tailed Sunbird occurs in closed-canopy forest and shrubland, forest edge and well-vegetated gardens and urban parks up to 700m altitude. They are often seen in urban areas visiting ornamental trees and shrubs.

There has been an increase in its distribution as shown by breeding and wintering atlas surveys. In the breeding season the percentage of occupied squares increased from 16.2% in 1993-96 to 21.8% in 2016-19, and in the non-breeding season this measure increased from 30.8% to 37.7%. It appears this increase is fairly general, but more noticeable on Lantau, western and northwest New Territories and, to a lesser extent, on Lamma Island. This is likely due to the maturation of shrubland and woodland habitat, planting and maturation of ornamental trees in urban areas and the spread of shrubs and trees in otherwise open country areas such as fish ponds. These figures also indicate that Fork-tailed Sunbird is more widespread in the non-breeding season, which involves a dispersal away from closed-canopy habitats to more open country and urban areas.

OCCURRENCE

Fork-tailed Sunbird was first recorded from 28 June to 14 July 1959 at Tai Po Kau. Subsequently, up to four were recorded at three sites on HK Island during January to April 1960, at least two birds were seen in Tai Po Kau around the same time and a female was seen at Three Fathoms Cove, Sai Kung on 14 October 1960. During the 1960s and 1970s there was a gradual increase in the number of sites at which this species was recorded to 20 in 1979. The pattern of records mirrored the present distribution, with most sightings from HK Island, the central New Territories and Sai Kung, and birds more widely recorded during winter than in the breeding season. It is notable that the only records during this period from other islands were of single birds on Lantau in October 1975 and December 1977.

Unfortunately, after about 1979, as Fork-tailed Sunbirds became increasingly common, reporting decreased, and it is generally not possible to track further changes in distribution or numbers. However, a slight spread was discernible on the islands. On Cheung Chau it was first recorded in November 1980 and was still only a rare winter visitor in 1995, but was present all year in 1997; however, it remains scarce and appears to be only a winter visitor there. In 1995 there was a winter record from Lamma where it has remained present though at low densities due to the relative lack of wooded habitats. It is now distributed on Lantau all year and appears to be continuing its increase there. On Po Toi it is a winter visitor from late October to mid-April, with one record in mid-May.

The highest count reported is 34 on 5 February 2016, but this and other high counts refer to large areas as this species does not form large flocks.

Matching its absence from HK until 1959, earlier observers found this species to be rather scarce in the Pearl River delta region. It was not recorded by Swinhoe (1861), while Vaughan and Jones (1913) knew it only from Ding Hu Shan, Guangdong where they considered it to be a winter visitor. However, La Touche (1925-30) reported it to be resident in hilly regions of both northern and southern Guangdong, and this distribution was reflected in the observations chronicled by Lewthwaite (1996) and Fellowes and Hau (1997). This species is rare in the captive bird trade in HK and, given the close proximity of its natural range to HK, its use of gardens and secondary woodland and its known tendency to wander in winter, there seems no doubt that Fork-tailed Sunbird is a natural colonist.

DIET AND FORAGING

Has been noted feeding on nectar and fruit of a wide variety of species, with Hong Kong Bauhinia Bauhinia blakeana, Rhodoleia championi and the exotic Coral Tree Erythrina speciosa and bottle-brushes Callistemon spp. particularly favoured. Other species include Bouganvillea sp., Camellia japonica, Calliandra haematocephala, Grevillea sp., Banana Musa x paradisea, Gardenia jasminioides, Hibiscus sp., Holmskioldia sanguinaea, Pavetta hongkongensis, Russelia sarmentosa, Salvia sp., Scolopia saeva, Stachytarpheta mutabilis, Tabebuia chrysantha and Tecoma stans.

BEHAVIOUR

Males often call while foraging making them relatively easy to locate, while females tend to be much more unobtrusive, vocalising much less. Favoured foraging areas can host several birds together, and in spring there is much vocalising at these sites. When in song males will remain stationary, often on exposed perches.

BREEDING

A nest with four chicks was found on 26 June. Juveniles being attended by adults have been noted from 20 March to 28 July.

RANGE SYSTEMATICS

Largely occurs in China, but also in northern and eastern Vietnam (Cheke et al. 2020). In China it occurs in southern provinces including Hainan from eastern Yunnan east through Guizhou, Hunan, Jiangxi and Zhejiang, though generally some distance south of the Yangtze. However, it also occurs in southeast Sichuan along the northern edge of the Yangtze, and also occurs up to the Yangtze in northern Hunan (Liu and Chen 2020).

A. c. latouchii occurs in all of China excluding Hainan south to central Indochina. Two other subspecies are also recognised, with the nominate confined to Hainan.

CONSERVATION STATUS

IUCN: Least Concern. Population trend decreasing.