IDENTIFICATION

VOCALISATIONS

The advertising call is the most familiar: a fairly loud and sudden ‘krrruk’, variable in pitch, often from dense cover.

 A variety of short calls are also delivered: ‘kik’, ‘kek’ or ‘keh’. In addition, a short or long series of ‘tit tit tit’ calls.

The agitation call is a fairly high-pitched ‘kwip’, uttered singly or in series.

DISTRIBUTION & HABITAT PREFERENCE

The stronghold of Common Moorhen is the wetlands of the Deep Bay area; it also occurs in small numbers in wetlands of the lowland northwest and northeast New Territories.

The breeding season distribution showed no substantial change between the breeding surveys of the mid-1990s and 2016-19, with no records south of a line from Tuen Mun to Tai Po. Away from Deep Bay, breeding season records occurred at Shuen Wan, Sha Tau Kok and the Ping Che area.

Winter distribution was slightly more extensive with records from the Nim Wan coastal area, Tai Tong, Shek Kong, Sha Tin, and on Lantau at Discovery Bay and near HK Disneyland Resort; only at the first of these sites were there records in the 2001-05 atlas.

In both seasons however, there was a decrease in the number of 1km squares in which the species was recorded: from 1.6% to 1.0% in the breeding season and 2.9% to 1.5% in the winter. There appears to have been a decline in the Deep Bay area, in particular in winter, presumably as a result sites at the margin becoming unsuitable and more intensive management of commercial fish ponds.

Common Moorhen occurs in wetland areas where there is some open water and emergent fringing vegetation. Thus, abandoned or inactive fish ponds, freshwater marsh and the gei wai at MPNR support birds, even where the water is rather eutrophic, as well as wet agricultural fields (in particular rice, though this is a rare habitat here).

OCCURRENCE

Figure 1 plots mean peak monthly counts in the Deep Bay area since the commencement of such surveys in 1998. It can be seen that wintering birds are present in broadly equal numbers from November to April. Substantial departure occurs in May and the summering population is present from June to September. The only record suggesting spring passage is that of one on the sea on between Sai Wan Ho and Po Toi on 29 April 2006.

Autumn arrival begins in October, which is when two of the most obvious instances of migrants have been recorded: a first-winter bird collided with a building in Central on the night of 28 October 1970 and one was recorded in nocturnal flight over Sai Kung West Country Park at 0045h on 21 October 2017. In addition, one was hit by an aircraft at the former airport at Kai Tak on 19 November 1975, another was found oiled there on the same date in 1976 and one was hit by a helicopter at 1930h and 130m altitude above Tai Long Wan on 13 December 1976.

Based on the peak winter counts of the species since 1979 there appears to have been a long-term decline since the late 1980s and early 1990s when between 120 and 140 birds were counted (Figure 2). Although there was an increase in the first decade of this century, in most winter periods since 2015/16 peak winter count has been 60 or fewer. Based on winter waterbird counts in Deep Bay Sung et al. (2021) concluded that the wintering population declined from 1998 to 2017.

Previous authors (Swinhoe 1861, Vaughan and Jones 1913) paint a picture suggesting that Common Moorhen was previously more common than is the case now, or even, perhaps, when Herklots (1953) noted its occurrence only in winter and spring.

BEHAVIOUR, FORAGING & DIET

It is omnivorous, with both plant matter and insects recorded as food items. It feeds while swimming or walking, either among vegetation or in the open.

Small groups occur in suitable habitat, with certain individuals asserting dominance over others with a charging attack, whereby a bird half runs half flies across the surface of the water toward its target. Common Moorhen are relatively shy, and frequently hide in vegetation at the approach of humans; however, they fairly quickly habituate to disturbance if it is relatively passive in nature.

BREEDING

Breeding takes place between late April and at least September (partly grown young have been seen from 15 June to early October), though most activity appears to occur from early June to late August.

RANGE & SYSTEMATICS

The nominate subspecies is distributed from Europe east through north Africa, west, central and south Asia to China, including Hong Kong. Other subspecies occur in central and south Africa, Indian Ocean islands, the Malay archipelago, Indonesia and the Philippines (Taylor et al. 2020). In China it occurs year-round in the southern half of the country and is a summer visitor to areas of the northwest and northeast (Liu and Chen 2020).

CONSERVATION STATUS

IUCN: Least Concern. Population trend stable.