The identification of Chinese Egret and Pacific Reef Egret
by Colin M. Poole, Jin-Young Park and Nial Moores, from OBC Bulletin 30, November 1999.
In Birding Sites in Malaysia, supplement to OBC Bull. 20 (1), plate 4 is labelled as showing a Chinese Egret Egretta eulophotes feeding alongside a Pacific Reef Egret Egretta sacra (reproduced on page 39, photo 1). However, in our opinion, both birds in this photo are Chinese Egret, with the bird on the right being in non-breeding plumage. We believe that the same error is also made in the first edition of Birds: A Photographic Guide to the Birds of Peninsular Malaysia and Singapore (2), where the photograph labelled as Pacific Reef Egret (photo 3) shows a similar non-breeding plumage Chinese Egret. The photographer, Morten Strange, informs us that both pictures were taken over the period 8–10th April 1991, at the northern banks of the Seleta River estuary on the coastal side of Khtib Bongsu, Singapore.
It appears that the identification of both birds was based primarily on bare-part coloration. However, we believe this should not be relied on for certain identification and it should only be used to support observations of more consistent structural characteristics.
We base our re-identification largely on the following characteristics:
Bill shape Chinese Egret typically has a more symmetrical bill, which is of a similar thickness for most of its length and only narrows in the last quarter towards the tip. This gives the bill a dagger-like profile. In Pacific Reef Egret the whole bill typically narrows gradually from the heavier-looking base. The culmen is rather more convex and the lower mandible straighter, with the upper mandible sometimes appearing to overlap the lower mandible at the tip. This gives the whole bill a rather more asymmetrical drooping, or droop-tipped, appearance.
Leg length Pacific Reef Egret has noticeably shorter legs than Chinese Egret, particularly in the tibia. In Pacific Reef Egret the tibia is significantly shorter than the tarsus so that all of the 'leg-length' appears to be in the tarsus. The legs also appear stouter, with chunkier knees in Pacific Reef Egret. In Chinese Egret the tibia is longer than that of Pacific Reef Egret, giving the slender legs a more balanced, proportioned appearance.
Jowl Pacific Reef Egret often appears heavy-jowled, but Chinese Egret never appears to show this feature.
Eye position and loral shape There appears to be a difference in the position of the eyes. In Chinese Egret the eyes are set noticeably above the gape. In Pacific Reef Egret they appear lower and closer to the bill. This difference is accentuated both by the apparent presence of a skeletal ridge above the eye in Chinese Egret, and by the difference in the shape of the loral skin. The latter appears narrower and more angled in Chinese Egret and broader and blunter in Pacific Reef Egret (often as wide as the bill at the bill-base).
Neck shape and posture Chinese Egret has a long, narrow neck, usually held in an S-shape curve, although it is held straight when the bird is alarmed. The back slopes down from narrow shoulders and the tertials are long and narrow, often overlapping the tail tip. Pacific Reef Egret has a stockier neck, often held hunched-up into its broader shoulders. The tertials appear blunter and broader, often completely obscuring the tail. As a result, Pacific Reef Egret appears overall a stockier and less elegant bird than Chinese Egret.
Bare part coloration In our experience, non-breeding plumaged Chinese Egrets can show a wide variation in bare-part coloration. Recent observations in Korea, Japan and Singapore, and studies of photographs, indicate that the bill is typically largely blackish, with the basal half to two-thirds of the lower mandible sharply edged strongly orange or yellow, sometimes extending just above the cutting edge in the final third. The legs are greenish (with feet near-concolorous), often with some obvious blackish scaling on the shins. The lores are greenish through to greyish, and the irides are a pale whitish-yellow
There is little or no information in the literature on the seasonal changes of bare part coloration of Pacific Reef Egret. However, our observations of dark-phase birds throughout the East Asian range (in all months) and white-phase birds in Singapore (in January) indicate that they show less clean-cut bills which are duller in dark-phase birds, with more extensively orangy-brown lower mandibles. In white-phase birds, the shins often lack the obvious scaling seen in Chinese Egret. Both phases have dark brown or yellow irides which appear duller than the pale irides of Chinese Egret.
A more detailed appraisal of bare part coloration of Egretta species in North-East Asia is in preparation by NM and he would welcome comments and observations on this topic sent to the address below.
Although outside the scope of this note, other features that can be useful when identifying Chinese Egret in the field are habitat preference and behaviour of the birds in question. Although Chinese Egrets utilise a variety of coastal habitats, they usually prefer feeding on intertidal mudflats. However, they roost on rocky shores, posts, islets or shingle banks and, where numerous, in tight groups. Pacific Reef Egrets prefer to feed on rockier shores or reefs, in areas influenced by wave action, often (though by no means always) occurring singly. Typically, Chinese Egret is more active when feeding and uses a variety of foraging techniques. One of these involves alternate walking and running through tidal-flat shallows, covering several hundred metres in a circuit. Others techniques include waiting (usually for shorter periods than other egret species) and, rarely, foot vibration. Pacific Reef Egrets appear more lethargic when foraging, usually carefully walking over smaller areas, waiting for long periods and rarely running.
We hope these features shed some light on the problems that have long hampered the identification of non-breeding Chinese Egret, and in particular their separation from white-phase Pacific Reef Egret. Accurate identification of birds in non-breeding plumage is essential in determining the distribution and numbers of this globally threatened species.
Acknowledgements We thank Morten Strange for his helpful discussions on this issue, for supplying further photographs of both species and for commenting on a draft of this note. We also thank Steve Henson for supplying photos of Pacific Reef Egret and the Natural History Museum, Tring, UK, for allowing PJ-Y to examine skins of both species in their collection.
Long, A. J. (ed.) (1994) Birding Sites in Malaysia. Supplement to OBC Bull. 20: 10.
Strange, M. and Jeyarajasingam, A. (1993). Birds: A Photographic Guide to the Birds of Peninsular Malaysia and Singapore. Sun Tree, Singapore.