IDENTIFICATION

VOCALISATIONS

The most frequent call away from the breeding colony is a deep and loud rattling croak usually uttered when flushed.

DISTRIBUTION & HABITAT PREFERENCE

Great Egrets occur in a wide variety of wetlands, but appear to favour shallow intertidal bays, commercial fish ponds and freshwater marshes; also occurs on soft shores, floating fish farms and very rarely in forest streams. Records are mainly from the wetlands around Mai Po and Inner Deep Bay, Starling Inlet and Shuen Wan.

OCCURRENCE

Figure 1 illustrates the pattern of occurrence in the Deep Bay area as recorded by systematic monthly counts since 1998 and indicates that numbers are highest in autumn, peaking in November, presumably due to the presence of passage migrants. The highest autumn count in HK is 1,315 on 14 November 2004 (with 2,058 in the whole of Deep Bay). In terms of birds seen on active migration, however, up to 500 have been noted per day from 24 August to 26 October, with all three-figure counts occurring from early September to mid-October. A gradual decline then occurs through the winter months to April, indicating that spring migration is relatively weak. This is reflected in the relatively few records of birds on active migration at this time, with up 38 birds noted from 5 March to 8 May, and a further record on 29 May.

From May numbers increase to July, which until recently was considered due to a large non-breeding population. However, in recent years a large breeding colony has been recorded in the mangrove area in Deep Bay (see below). The highest midsummer count is 816 on 5 July 2020 (no doubt reflecting the presence of breeding birds), while a count of 1,199 was made on 16 August 2020. Interestingly, the highest midsummer count until 1991 was only 20 birds.

Figure 2 illustrates the peak winter period count since 1979 in the winter waterbird monitoring programme. On the HK side of Deep Bay numbers were generally between 400 and 600 until winter 1999/2000, after which there was an increase to between 800 and 1,200 up to winter 2018/19, with the highest count being 1,218 on 9 December 2018. In the whole of Deep Bay, midwinter counts peaked at 1,941 on 12 December 2004, after when numbers recorded on the Shenzhen side of the bay declined. A similar trend is apparent for Little Egret.

There is one record of the nominate taxon, a bird at Shuen Wan on 7 February 2017 (Allcock 2021).

Vaughan and Jones (1913) suggested that Great Egret was an occasional winter and spring visitor to the coast of Guangdong whilst Macfarlane and Macdonald (1966) reported that the species was seen in the Deep Bay marshes through most of the year, but particularly in winter.

BREEDING

The first breeding record occurred at Yuen Long egretry in 1959. The next record was not until 1977 at Mai Po and possibly at Yim Tso Ha egretry. Yim Tso Ha then became a long-term though irregular breeding site for the species with up to three pairs present. Breeding at the adjacent island of A Chau in Starling Inlet was first recorded in 1981; the number of breeding pairs was approximately four until the early 1990s, and numbers increased to 30 pairs in 1997.

Breeding was first recorded at Yuen Long egretry in 1959. The next record was not until 1977 at Mai Po, though it possibly also bred at Yim Tso Ha in the same year. In 1997 a pair bred at Penfold Park, Sha Tin.

The number of pairs of breeding Great Egrets in HK was no higher than 82 until 2002, after which there was a gradual though irregular increase to 167 in 2012 and 283 in 2015, followed by a sharp increase to 803 in 2020. Figure 3 illustrates the pattern of Deep Bay and non-Deep Bay area nest counts and indicates that until 2014 rather few birds nested in the Deep Bay area. However, since then, and particularly with the discovery of a large nesting colony in the intertidal mangrove in 2019, the number recorded has been much higher.

BEHAVIOUR, FORAGING & DIET

Large numbers congregate at fish ponds in the process of drain down and it roosts communally throughout the year. So and Yuen (2020) surveyed ardeid roost sites across Hong Kong in winter 2019/20 and recorded 1,201 Great Egrets across 23 of the 26 known roost sites, with highest numbers in Deep Bay, around Tolo Harbour and at Ap Lei Chau and Sha Chau. The highest single roost count is 887 at Tam Kon Chau on 8 February 2007, with other counts of over 700 having also occurred at Mai Po NR and Lok Ma Chau MTRC wetland mitigation area.

Prey items noted are fish, mudskippers, small shorebirds and dragonflies (Pantala flavescens). Viney (1989) noted a Great Egret swimming while feeding.

Appears to be exclusively a diurnal migrant, as there are no reports of birds departing on migration at dusk or on nocturnal migration.

RANGE & SYSTEMATICS

Worldwide distribution between 50oN and 50oS with most breeding populations north of 30oN migratory, especially in north America and Asia (McCrimmon et al.  2020). In China a summer visitor to the northeast and northwest, and present all year in southern coastal provinces, including Hainan and Taiwan (Liu and Chen 2020).

Four subspecies are recognised, of which two are considered to have occurred in HK. The default taxon is A. a. modesta, which occurs from south and east Asia to Indonesia and Australasia. In addition, there is a single record of the nominate form (Allcock 2021), which occurs from central Europe to northeast Asia and south to Africa and south Asia. The remaining two subspecies occur in sub-Saharan Africa and the Americas.

CONSERVATION STATUS

IUCN: Least Concern. Population trend unknown.