Daily Archives: 20/01/2021

Western Water Rail Rallus aquaticus: Incheon, January 2021. Notes on Identification.

Dr Nial Moores, January 20th 2021

In December 2020, Lee Jae-heung found a Western Water Rail Rallus aquaticus, presumably of eastern subspecies korejewi, wintering in a semi-urban stream in northern Incheon.  Once the news went public in January, the bird was seen and photographed by perhaps hundreds of birders and bird photographers – including several Birds Korea members. This record provides an excellent opportunity to build on our last ID note on this species, posted back in 2014.

Water rails in juvenile plumage might or might not be difficult to separate to species. However, based on personal field-impressions of both species and on a comparison of some wonderful images generously shared for this online note (with copyright retained by the photographers), at least from October Western Water Rail should be straightforward to separate from Eastern Water Rail Rallus indicus (often called Brown-cheeked Rail), even in brief views.

  • Western Water Rail has a substantially more delicate-looking structure than Eastern Water Rail, especially when neck-stretching (a frequent behaviour).  Eastern looks bulkier, thicker-necked and heavier-breasted, almost Moorhen-like, with thick legs and a “big back-end”.
Western Water Rail, January 2021, Incheon, ROK © Shim Kyu-Sik.
Eastern Water Rail, November 2020, ROK © Elizabeth Skakoon
  • Western Water Rail has brown-washed breast sides but is more or less grey-blue across the centre of the breast. Eastern Water Rail usually shows extensive brown tones on or even fully across the breast.
Western Water Rail, January 2021, Incheon, ROK © Shim Kyu-Sik
Eastern Water Rails November 2020, ROK © Elizabeth Skakoon
First-winter Eastern Water Rail, March 2013, Hong Kong © Paul Leader
Adult Eastern Water Rail, November 2011, Hong Kong © Paul Leader
  • As shown in the images above and below, Eastern Water Rail has a much more contrasting head pattern than Western Water Rail, superficially recalling some online images of juvenile Western Water Rail taken in the west of the range.  Like some juvenile Western Water Rail, both First-winter and adult Eastern Water Rail seem to show obvious paleing on the supralorals; a whiteish or pale throat; extensive dark across the lores and below the eye contrasting with a pale eye-ring, and dark across part of the ear coverts. However, Eastern Water Rail also (always?) shows very dark, even blackish, crown sides and a very dark forehead down to the bill base. Western Water Rail look much plainer on the head. Even in poor light, the crown sides do not look obviously darker, and the forehead, while dark, is still brown-toned, and slightly paler than the blackish centres to much of the upperparts. As a result, Western Water Rail in mid-winter tend to look rather open-faced, puzzled or surprised-looking even, while Eastern Water Rail tend to maintain a somewhat disapproving frown.
Western Water Rail, January 2021, Incheon © Amaël Borzée
Western Water Rail, January 2021, Incheon © Nial Moores
Eastern Water Rail, October 2015, Suncheon © Matt Poll
  • The pattern of the undertail coverts are strikingly different. Both have short brown tails, with a mix of buff and white on the undertail coverts. However, in Western Water Rail, the white is clean and unspotted and the buff is bright, with only isolated dark spots (at least in both well-photographed Korean Western Water Rails).  The field impression from the side and rear of Western Water Rail therefore is of Moorhen-like white which edges a rich butterscotch brown. Eastern Water Rail is much more heavily marked, with extensive black across all of the undertail coverts, with this spotting or blotching clearly visible from the sides.  
Western Water Rail, Gangneung, December 2014 © Park Dae-Yong
Western Water Rail, January 2021, Incheon © Nial Moores
Eastern Water Rail, November 2020, Republic of Korea © Elizabeth Skakoon
First-winter Eastern Water Rail , March 2013, Hong Kong © Paul Leader
Adult Eastern Water Rail, October 2014, Hong Kong © Paul Leader
  • Bare parts colour seems more intense in Western Water Rail than in Eastern Water Rail. The iris in Western looks redder, and the red on the bill is extensive, covering much of the lower mandible, and also running above the cutting edge of the bill. In Eastern Water Rail, the lower mandible usually looks orangey, and this colour often seems to be confined to a narrow wedge at the base of the upper mandible.
Eastern Water Rail, January 2014, Poyang Lake, PR China © Vaughan Ashby
And for a final comparison, two Western Water Rails from much further west: October 2020, Northern Negev, Israel (Left); and in-hand photo, January 2010, Ashdod, Israel © Yoav Perlman. Both individuals show e.g., the slender profile, plain grey “face”, clean-looking grey breast, and intense reddish irides and lower mandible of Western Water Rails seen in Korea. The undertail coverts of the bird in the hand look more densely and boldly patterned than birds photographed further east in Korea and in PR China. Nonetheless, unlike in Eastern Water Rail, they are still bordered with un-spotted white.

Likely Status of Eastern and Western Water Rails in Korea

Contrary to much online information, there is still no evidence that Eastern Water Rail breeds anywhere on the Korean Peninsula. Although likely often overlooked, based on images, published literature and resources like eBird, the Eastern Water Rail remains a scarcely-observed migrant and winter visitor to the ROK with less than 100 records annually, and most records between October and March.  Recent research effort in the DPRK has also not added to the five records of “Water Rail” listed by Tomek (1999) for that nation, even though much of our own research in 2014-2019 in the DPRK was conducted in potentially suitable habitat for the species.

Western Water Rail appears to be even rarer in Korea.  The Incheon bird was the first to be properly twitched and might be only the fourth (?) national record. Previous ROK records known to us have been between November and January, i.e. one photographed in Shihwa Lake, Gyeonggi Province in c. 2010; one photographed in late November Gangneung, Gangwon Province, in 2014; and one seen and sound-recorded (poorly) on Baekryeong Island, Incheon, in November 2016.

Acknowledgements

Our sincerest thanks to Dr. Shim Kyu-Sik, Dr. Elizabeth Skakoon, Prof. Amaël Borzée, Prof. Todd Hull, Dr. Yoav Perlman and Messrs. Vaughan Ashby and Matt Poll for sharing their superb and instructive images for use in this online note; and warm thanks once more to ID pioneer Paul Leader and Mr. Park Dae-Yong for their images first shared with us back in 2014, and re-used here.

Reference

Tomek, T. 1999. The Birds of North Korea. Non-Passeriformes. Acta Zoologica cracoviensia. Vol 42.