White-breasted Waterhen Amaurornis phoenicurus 白胸苦惡鳥
Category I. Common resident in a variety of freshwater and brackish wetland habitats, though numbers are declining probably due to urbanisation of the New Territories.
IDENTIFICATION
Jan. 2022, Michelle and Peter Wong.
28-33 cm. A medium-large rallid that is highly distinctive in adult plumage due to the contrast between the dark brownish-grey upperparts from mid crown to tail and pure white underparts from forecrown and face to belly. The vent and undertail coverts are bright rust. The bill is lime-yellow with a red base to the upper mandible, the eyes are dark red and the legs and feet are orange-yellow.
Jul. 2007, James Lam.
Immature birds are much duller, with greyish upperparts, sullied whitish underparts and dull brownish-buff vent and undertail coverts. The bill is largely greyish-pink, and the legs and feet are dull brownish.
May 2007, James Lam.
Recently fledged juveniles, which are usually seen in the company of adults, are all dark. This bird is older and moulting into immature plumage.
VOCALISATIONS
Diverse, often loud and usually uttered from hidden sites, though these may include the near the top a bush. The loud and distinctive song is a single ‘twok’ or ‘tok’ repeated just over twice a second often in the evening or at night. This may be uttered for periods of up to 15 minutes, presumably by the male.
The same note can be heard as part of what appears to be a duet vocalisation of a pair that also includes a variety of croaks, cackles, squeals and bubbling calls, given at intervals as the pair forage together.
A single relatively quiet and low-pitched ‘tuk’ or ‘chik’ note may be uttered for long periods of time while foraging.
The alarm call is a repeated relatively high-pitched ‘pwit’ or ‘pwoot’.
DISTRIBUTION & HABITAT PREFERENCE
White-breasted Waterhen occurs in a wide variety of wet habitats from intertidal mangroves, freshwater marsh, reed marsh, riverine vegetation, damp shrubland to wet agricultural areas and associated ditches or channels. It does not shy away from areas of human habitation, though it appears to have disappeared from Hong Kong Island.
Not surprisingly the lowland areas of the northwest New Territories are the stronghold. It also occurs at much lower densities around Tolo Harbour and in Sai Kung and Clearwater Bay, as well as on Lantau and Lamma Islands.
The 1993-96 breeding atlas recorded White-breasted Waterhen in 18.2% of squares, but in only 9.6% of squares in the 2016-19 atlas. The winter atlas surveys also saw a decline though a smaller one, from 10.3% in 2001-05 to 8.6% in 2016-19. Given the higher number of vocalising birds and consequent greater likelihood of being recorded in spring, the breeding bird survey results are probably a more accurate reflection of its distribution and decline.
While it remains in core Deep Bay areas, it appears to have declined in areas at the periphery to the southwest and northeast, as well as further south around Tolo Harbour (particularly on the south side where development of Ma On Shan has occurred) and Sai Kung. The sole 1km square on Hong Kong Island in which occupancy was recorded in the 1993-96 breeding atlas appears to no longer be occupied. It may also have disappeared from isolated islands such as Tai A Chau in the Soko Islands and Crooked Island, where it was formerly present.
OCCURRENCE
As Figure 1 indicates, White-breasted Waterhen is present all year in the Deep Bay area, and the pattern of occurrence probably reflects the higher visibility of birds during the breeding season, when males are vocalising for courtship and territory and, later, when juveniles are present.
Figure 2 plots peak winter waterbird counts since 1979. The highest count is of 75 on 12 January 1975; given its shy and unobtrusive behaviour, this is undoubtedly a substantial underestimate of the numbers actually present. It is difficult to know whether the variation in numbers recorded reflects actual changes.
Despite its skulking habits, White-breasted Waterhen is sufficiently common to be regularly seen in its core areas of occupancy. Some local expansion into areas formerly unoccupied occurs, but not at a scale to suggest substantial immigration. Figure 1 indicates an increase in the number of birds present in October, and an adult was struck by a helicopter between Tung Chung and Pak Mong at 1910h on 4 November 2000, which together suggests weak autumn passage. It is a summer visitor to parts of central China and a scarce but increasing migrant through the Beijing area (Birding Beijing 2022).
BREEDING
Recently fledged chicks have been noted from late March to early September, though more regularly from mid-April to August. Vaughan and Jones (1913) reported the breeding season as lasting from May to August, with six eggs usually laid.
BEHAVIOUR, FORAGING & DIET
Forages at ground level or just below the surface of the water. It is presumed that the diet constitutes invertebrates, insects and small aquatic animals, and possibly the shoots or roots of wetland plants.
Generally skulking, though not particularly shy. More obvious in the breeding season when pairs can fairly often be seen together. Forages in close proximity to man if there is sufficient vegetative cover. Active at night when it can vocalise for long periods of time. Flushes fairly readily, and swims quite well.
RANGE & SYSTEMATICS
Largely resident from the Indian subcontinent east to the southern half of China (in much of which it is a summer visitor), south through southeast Asia the Philippines to Indonesia (Taylor 2020). In China it occurs in the southern part of the country as far north as the Yellow River, with more northerly birds being migratory (Liu and Chen 2020). A scarce but increasing migrant through the Beijing area (Birding Beijing 2022).
Three subspecies are recognised, with the nominate occurring in much of the range from the Philippines and the Malay archipelago north, including HK.
CONSERVATION STATUS
IUCN: Least Concern.
Figure 1.
Figure 2.
Birding Beijing (2022). https://birdingbeijing.com/the-status-of-the-birds-of-beijing/ (Accessed 5 December 2022).
Liu, Y. and Y. H. Chen (eds) (2020). The CNG Field Guide to the Birds of China (in Chinese). Hunan Science and Technology Publication House, Changsha.
Taylor, B. (2020). White-breasted Waterhen (Amaurornis phoenicurus), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.whbwat1.01
Vaughan, R. E. and K. H. Jones (1913). The birds of Hong Kong, Macao and the West River or Si Kiang in South-East China, with special reference to their nidification and seasonal movements. Ibis 1913: 17-76, 163-201, 351-384.
