Written by Dr. Nial Moores of Birds Korea
As part of the fledgling Species Action Plan and Task Force (under the EAAFP), we were asked by the coordinator to collate records of the now Critically Endangered Baer’s Pochard Aythya baeri in Korea. We were able to trace about 20 records in the Republic of Korea (ROK) since 1994, though undoubtedly a few more records exist and we still welcome receiving any reports of this species on the Korean Peninsula, however old or recent (please with date, location, sex and age, and an indication of whether there are images or not).
Most of the records in the ROK were pre-2002, including the national high count: five in the Nakdong Estuary in January 1995 (listed in Park Jin Young’s 2002 doctoral thesis). There have been several recent winters with no records; there was only one record we know of last winter (a well-watched male on the Han River: see below); and it appears that there might have been no records this winter at all.
In the past decade, it also appears that there have been more observations here in the ROK of (male) Aythya that show some Baer’s-like features than birds that actually look like pure Baer’s Pochard. Based on images publicly posted in Japan in winter in recent years, it also seems that there are rather more birds there also showing anomalous features than birds that do not. Some of these anomalies might be part of individual variation, some likely indicate hybridisation. Fortunately, ID criteria should be much better know within 1-2 years, once the results of WWT’s genetic tests have been completed on the captive Baer’s Pochard population, and a gallery of birds of known (rather than suspected) provenance has been established; and once the species has also been better-studied at known breeding sites.For now though, with every record of this now extremely rare species important to gather and review, how to identify Baer’s Pochard?
Adult males are actually quite striking and attractive birds to look at; something expressed by quite a few other observers when they first see the species.
Structurally, they look wide-bodied, large-headed, have quite rounded crowns (lacking the peak to the crown of Ferruginous Duck) and they “feel” large billed (an effect probably accentuated by the pale grey and blue tones to the bill, with black confined to the nail and the cutting edge).
The fore-flanks have obvious white patches, easy to see at all times above the water line, sometimes slightly striped looking. There are additional “tiger-stripes” to the rear of the white (these stripes can be very striking in the field and were one of the main features I used to confirm my first few Baer’s). The head is green: not quite Mallard-green, but close. At certain angles, this green can just look quite dark. The breast is reddish-brown, often looking fiery, or coppery in strong light (giving the bird its Korean name), and sometimes appearing browner, adding to its “Mallard look”. The rest of the upperparts are dark, in shade sometimes looking blackish, with a hint of warmer tips to the upperparts in fresh plumage, and perhaps a slight purpley gloss when worn. The vent is white, cleanly framed above and on the leading edge with dark. The plate in Madge and Burn’s 1989 identification guide Wildfowl shows a somewhat two-tone appearance to this dark (black above, fading to brown). The spread wing shows very extensive white (a feature pretty much shared with Ferruginous Duck). And like male Ferruginous Duck, the eye is also very pale, though usually yellowish-white or greenish-white (“sometimes very pale yellowish”: Madge and Burns) rather than white or blue-white.
Features of eclipse males and First-winter males seem to be less well-known than the adult males, and need to be refined. (If you have experience and can share it here, please do through the comments section.)
One old source (“A Natural History of the Ducks: Plectropterinae, Dendrocygninae, Anatinae” by John Charles Phillips, 1922) apparently states that “Males in captivity did not “go off” in colour to any appreciable extent when in eclipse; although they assume a rusty facial patch and get some white mottling on the breast. At this time also the white appears to “fade” off the flanks in both sexes” (thanks to James Holmes and the Kantori List-serve group). Another source, Ducks, Geese and Swans(edited by Janet Kear and published by the Oxford University Press in 2005) notes that at least some male Baer’s Pochard are in nuptial plumage (=breeding plumage) in August. My own experience is much more limited, but I have seen one or two full adult male Baer’s Pochard at least as early as October.
Ducks, Geese and Swans describe the female thus: “superficially resembles male, but has dull brown head and chest, brown iris and subtle pale brown patch between bill and eyes”.
Indeed, the few (adult-type?) females I have seen also seemed fairly straightforward to identify. Females simply looked like a dull, dark version of the male, with the same head shape, same large-looking bill (though darker), same obvious white foreflank patch and stripey flanks; similarly dark brown upperparts (though perhaps a shade paler than the male?); the same clean marked-off vent; and the same clean white wing-stripe. Instead of a clean green head, the head looks darkly brownish-blackish-green, with a more or less obvious paler rusty patch on the lores, towards the bill base. Madge and Burn’s Wildfowl add that females “often” have “some whitish mottling on the throat” and that the iris is dark. It seems that the eye can appear more obviously bicolored when seen well or in strong light. The illustration of a female in Madge and Burn’s Wildfowl captures all of these features well.
A photo of a female in Tadao Shimba’s (2007) Photographic guide to Birds of Japan and North-east Asia (taken in Fukuoka in December) shows a bird with a very dark eye and dark head, a rather darker-grey toned bill than in males, upperparts as dark as a male, some mottling to the lower edge of the breast, and only a weak suffusion of brown on the lores at the bill-base. It also shows an obvious white foreflank patch and some tiger striping (paler bars) across the rear flanks. It therefore more or less matches the illustration of the immature in Madge and Burn’s Wildfowl, and perhaps could be a First-winter female (?).
Juvenile / Immature (July-November?)
Immature plumages do seem to be less well-known. Most Aythya (and therefore presumably Baer’s Pochard too) have a head and body moult during their first winter. Wing-feathers tend to be (largely) un-moulted, presumably creating moult contrast once a bird starts to mature. Ducks, Geese and Swans states simply that the immature looks “as adult female, but has russet brown abdomen”, a feature not shown in Madge and Burns. An immature male that has not yet started moult perhaps should have a russet brown abdomen (or some russet brown wash there) and look dark-eyed; and one that has started to moult should show white appearing on the vent; paleing (brown) eyes; green replacing brown on the head; and some moult contrast.
According to Madge and Burn, the Juvenile “resembles female, but duller with head and neck dull buffish-brown, contrasting a little with the darker crown and hindneck and and reddish-brown breast; white of belly suffused brownish but white on fore-flanks relatively extensive. Assumes adult plumage during first autumn and winter.”
One male at Junam (ROK) in February 2008, photographed at distance, showed some paler area towards the bill-base; intermediate-colored eyes; some brownish wash to the green of the head; and brown on the scapulars. It otherwise looked just like the adult male Baer’s Pochard which was less than 10m away from it. It was therefore identified as a First-winter male (in its Second Calendar-year). See image 268 in our Gallery.
All of the above suggests that Baer’s Pochards really should look like Baer’s Pochard, at least from late autumn onwards.
Baer’s Like Birds
So what then to make of this individual in the collection at Martin Mere in the UK photographed earlier this month? The Baer’s Pochards in the WWT collection have a long history of captivity, and there is therefore the possibility that some individuals are the result of hybridisation (hence the need to genetically test them). Is this an eclipse male Baer’s? A Second Calendar-year male Baer’s? An old female Baer’s? Or a Baer’s like hybrid (perhaps with some “old” Ferruginous genes?)?
Although showing multiple features expected in a Baer’s, it also shows much more than “subtle” russet-brown at the bill base (not only on the lores, but apparently onto the forehead too); a greatly reduced white fore-flank patch; a much reduced contrast between the breast and the flanks; black extending (just) off the nail but not along the cutting edge; and a grey and brown iris. In this one image, the head also looks a little peaked. If it is a pure Baer’s, then it seems to complicate identification of hybirds even further!Images of Baer’s like birds this winter from Japan and the ROK (as recently as March) also show birds with one or more anomalous features, many perhaps a little more striking than in the image above, including e.g.:
- A sharply-peaked crown;
- A lack of white foreflank patch;
- A lack of flank stripes;
- Muted tones to the breast in adult males and / or weak contrast between the head and breast;
- Common Pochard-type orange on the crown;
- Presence of Common Pochard-grey (in the upperparts and / or wing-stripe)
- Presence of vermiculations (even though faint);
- Poorly marked off vent, in what otherwise appears to be an adult;
- Black on the bill extending obviously off the nail;
- Dark grey tones to the bill in pale-eyed (=adult male) birds.
It would seem wisest to document such birds as carefully and as fully as possibly, and to consider them as hybrids (or as Baer’s like birds) until Baer’s Pochards of known provenance are proven to show the same features (so that such features can no longer be considered as anomalous).
For now, Aythya and ID experts are invited to review some of these online images and to help determine objectively which species might be involved. Some e.g. green-headed birds that show several anomalous features might not even have Baer’s Pochard genes in them (see Gillham et al. (1966)); some others seen over the years seem to suggest hybridisation betweenFerruginous Duck and Baer’s Pochard; Ferruginous Duck and Common Pochard; and perhaps Baer’s Pochard and Common Pochard (including the 2015 bird on the Han River?) .
Accepting that the vast majority of Baer’s like birds showing multiple anomalous features are hybrids should be fairly straightforward, as hybrid Aythya are frequently seen by birders in other parts of the world. However, a recent email chain on the Kantori Listserver (the reason for this extended note) suggested otherwise. Reasons for rejecting this approach seem to include (1) The lack of good published information on Baer’s Pochard, especially non-adult male plumages so that potential variation is not yet well-understood; and (2) The unlikelihood of hybrids outnumbering pure Baer’s Pochard in Japan or anywhere else.
The first point should be addressed in time by the research being conducted by the WWT and in the field in China, and I hope is at least part-addressed by the images above.
The second can be explained simply by understanding that Baer’s Pochard is now extremely rare, so that everyone is starting to look for it; it seems to be undergoing range contraction (even while species like Ferruginous Duck appears to be expanding its range in East Asia), so that the part of the population that used to migrate regularly to Korea and Japan might effectively no longer exist; and these hybrids (while still probably a tiny number of individuals) are only likely to be obvious and numerically dominant at the edge of the range of the species, in areas with very few pure Baer’s but with many birdwatchers, photographers and well-watched wetlands (e.g. in Japan and the ROK). Hybrids are thus likely to be much less numerous (at least proportionately), and less photographed, in core breeding and wintering areas that hold more pure birds (i.e. in parts of China).
Images and comments are welcome.
And finally, many thanks to Pete Morris (of Birdquest) and Prof. Robin Newlin for permission to use their images; and to Kantori for hosting a lively discussion on these birds.
Original article: http://www.birdskoreablog.org/?p=14726
To find out more about Baer’s Pochard, please click here.