IDENTIFICATION

VOCALISATIONS

Generally silent away from the breeding site apart from quiet, throaty grunts in flight or when disturbed.

DISTRIBUTION & HABITAT PREFERENCE

Previously, paddy was the preferred feeding habitat for Eastern Cattle Egrets, and birds would often be seen feeding around water buffaloes. With changes in land use over the past 50 years, however, they have adapted to other habitats such as the grassy margins of wet and dry agricultural areas and commercial fish ponds. Around Mai Po, Young (1998) found that they fed almost exclusively along fish pond bunds.

Eastern Cattle Egrets have also been attracted to feed at refuse sites. From 1992 until its closure in 1996 up to 145 were recorded feeding at the Shuen Wan refuse landfill. This availability of insect food would explain the use of the nearby Shuen Wan fung shui wood as a breeding site by up to 75 pairs during roughly the same period; numbers using this wood as a breeding and roosting site declined once the landfill closed.

Eastern Cattle Egrets also frequent areas of short grass such as the golf courses at Fanling and Kau Sai Chau, around water sprinklers on sports grounds and on airfields.

Records from the New Territories, both in the northwest (e.g., Mai Po, Lok Ma Chau and Long Valley), northeast (e.g., Sha Tau Kok) and east (e.g., Ho Chung and Sai Kung). In addition, there are also records from Hong Kong and Lantau.

OCCURRENCE

Whilst Swinhoe (1861) and Kershaw (1904) stated that Cattle Egret was common, Vaughan and Jones (1913) stated that it was ‘an occasional visitor on spring and summer migrations.’ Herklots (1953) suggested that the explanation for this apparent difference in status could be variations in the numbers present between years. He noted, for example, that the species was more common in 1928, when he first arrived in HK, than when he left in 1948.

Herklots (1941, 1953) also stated that the species was a breeding summer visitor, arriving between 30 March and 13 April, and suggested that some might remain for the winter. By the mid-1960s however, whilst it was still predominantly a summer visitor, there were occasional records from winter and the first arrival date was earlier; extreme dates quoted by Macfarlane and Macdonald (1966) were 10 February to 12 November.

Over the decades, therefore, Eastern Cattle Egret has slowly increased to such an extent that they can now be found throughout the year in the Deep Bay area (Figure 1) and other sites in the New Territories, particularly Long Valley. In the Deep Bay area numbers are highest in the wet season from April to October. Passage birds appear to be responsible for higher numbers in April and May, locally-bred birds in July and migrants again in September and October. The same pattern is probably true for much of the New Territories. The presence of migrants on Po Toi, where the species does not breed, or over nearby waters from 23 March to 4 June (highest count 113 on 1 May) and from 2 September to 12 November (highest count 82 on 8 October) is a good indicator of passage periods.

Figure 2 illustrates peak Deep Bay area winter waterbird counts since 1979 and indicates in most years fewer than 200 birds are present, though an exceptional 360 were counted in 1989/90.

The highest count is of over 1,000 individuals emerging from a roost in the mangroves at Mai Po on the morning of 29 August 1977; on 24 July 1979, a count of 850 birds flying to the same roost was made. The highest count since 1999 is 600 in Tung Chung Bay on 24 September 2003.

BREEDING

Eastern Cattle Egrets have bred in Hong Kong since at least 1941 (Herklots 1941), and the first recorded colony was at Yuen Long where there were usually 60 pairs (Herklots 1967). In the mid-1960s Yim Tso Ha supported the only breeding population after the abandonment of colonies at Hang Ha Po and Yuen Long (Macfarlane and Macdonald 1966). This remained the main breeding site until it was abandoned in 1994. The birds then moved to the adjacent island of A Chau, where a peak of 68 pairs bred in the first year. The average number of pairs in HK as a whole was 73 in the period to 1995 (though surveys were not annual).

Figure 3 illustrates the number of nests recorded in annual surveys since 1998. Until recently, the highest number of breeding birds was outside the Deep Bay area; indeed, the period 2010-14 saw no nests at all in Deep Bay. The mean number of nests was 70 from 1998 to 2010, since when the mean is 41. However, a newly-discovered egretry in the intertidal mangrove area of Deep Bay held approximately 70 birds in 2020 and 2021, while the number of breeding pairs away from Deep Bay was low.

The breeding cycle appears closely tied to the wet season, with dry springs appearing to result in later nesting or fewer pairs.

BEHAVIOUR, FORAGING & DIET

Although in many parts of the world associated with cattle or other ungulates, which are followed in a search for disturbed invertebrates, there are relatively few of these in HK and so Eastern Cattle Egrets are usually seen foraging in small to medium size groups in vegetated parts of freshwater or brackish wetland areas such as marsh or commercial fish pond areas.

Previously, when fishermen would leave piles of dead fish of low commercial value (Tilapia spp.) to rot along the pond bunds, these would attract large numbers of flies on which Eastern Cattle Egrets would feed (Melville 1990, Young 1994). However, this practice ceased in the mid-1990s. Also recorded feeding on insects and invertebrates disturbed by foraging cattle and water buffalo, dragonflies (including Pantala flavescens) and frogs.

Quiet, unobtrusive, gregarious and not particularly shy in the presence of man. Foraging requirements mean birds forage together in loose flocks and apart from other egrets and herons.

RANGE & SYSTEMATICS

Monotypic. Worldwide distribution between 50^oN and 50^oS. Mostly resident in the southern hemisphere, with migratory populations in U.S.A., parts of Europe and east Asia (Telfair 2020). In China present all year in the southern third of the country and a summer visitor to areas as far north as Hebei province (Liu and Chen 2020).

CONSERVATION STATUS

IUCN: Least Concern. Population trend increasing.