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41–47 cm; male c. 880 g, female c. 680 g (1); wingspan 70–79 cm (2). Small, compact duck with very dark general coloration and large white wingbar distinctive in flight (1) (being duller, especially on primaries, than A. nyroca) (3). Generally resembles A. fuligula, but rounded head and bill shape recall A. ferina (2), with larger bill than A. nyroca (3). Male has green-glossed head and neck in breeding plumage, blackish-brown upperparts , dark chestnut breast, paler chestnut and white flanks , white vent (recalling A. nyroca, which is overall more rufescent and smaller) (1), small white spot on chin, bill dark grey becoming bluer towards tip with black nail, and sometimes pale yellow iris instead of white ; has eclipse plumage in which breast is more vividly coloured than that of adult female (1). Female duller with blackish-brown head blending into chestnut-brown breast and flanks; has dark rufous spot between bill and eye (lacking in eclipse male), and inconspicuous small white spots on neck; underwing largely white; iris dark brown. Juvenile resembles female with russet-brown on abdomen; first-winter also like female, but much duller and browner, often having pale-marked breast, and has smaller (or no) paler patches at bill base and on fore-flanks (3).
Amur and Ussuri basins in SE Siberia and NE China; recently recorded breeding in C China (Hubei) (4); perhaps also N Korea. Winters mainly in E & S China, also NE India to Vietnam, and Taiwan.
Preferably in open country, on well-vegetated pools, small lakes and slow-flowing rivers with ample emergent vegetation (2). In winter frequents larger waterbodies, including marshes, coastal lagoons, reservoirs (1) and estuaries.
Migratory; leaves breeding grounds in Sept–Oct (1) after moult to winter in coastal plains of SE China and several scattered localities westwards to NE India and southwards to Indochina; a few may winter in South Korea and Japan. In India, very uncommon and erratic away from NE (mainly Assam, where three seen in Feb–Mar 2015 (5, 6), but also Sikkim (7), Tripura (8) and at least formerly in Manipur) (9), with only very occasional records in Uttar Pradesh (10), Uttaranchal Pradesh (11) and elsewhere. Records in Taiwan span the period mid Oct to late Mar (2). Vagrant to Kamchatka, Pakistan (Punjab, Jan 1957) (12) and the Philippines (five records, most recently on Luzon in Jan–Feb 2015) (13, 5), with just two records in Bhutan (Mar 1994 (14), Apr 1998) (15) and one in Laos (early 2000), although speculated that species was perhaps regular in latter country in 1980s, when reasonably large numbers still occurred in adjacent Thailand (16).
Diet and Foraging
Little known, but evidence suggests both plant and animal materials consumed, with rice an important food in some areas and small frogs also reported (1). Probably obtains major part of food by diving. Preliminary activity budget data from Bangladesh (in winter) revealed that species spent most time between 08:00 hours and 14:00 hours resting (58%) and swimming (32%), and considerably less time foraging (7.4%) and preening (2.6%), but were most actively foraging and swimming prior to 10:00 hours and primarily stationary (either resting or preening) after 10:30 hours (17). Single pairs or small groups usually encountered in breeding season, while in non-breeding season often consorts with other ducks, in Bangladesh, for example, Netta rufina, Mareca strepera, Anas crecca, Aythya nyroca and A. ferina (17); sometimes in large flocks, at least formerly (1).
Sounds and Vocal Behavior
Generally silent, especially in winter (3), but both sexes said to give harsh “graaaak” in courtship, while at other times male utters “koro koro” and female a “kura kura kura” (2), generally reminiscent of A. ferina (1).
During local spring, usually arriving on breeding grounds during Apr, but sometimes as early as mid Mar and as late as mid May, with laying starting late May to early Jun; broods seen on L Khanka (Russian Far East) as late as mid Aug (1). Nest is scrape (155–180 mm by 55–120 mm) on ground amid dense cover (e.g. Carex, Zizania caduciflora, Typha sp. grasses) (4), sometimes with gulls (Larus) or terns (Chlidonias) (4), lined with vegetation and down feathers (1). Clutch 6–13 cream-coloured eggs, mean size 51 mm × 38 mm, mass 39·3–42·8 g (1, 4); incubation c. 27 days (captivity); newly hatched chicks weigh mean 24·2 g, similar in appearance to those of A. marila, but crown slightly darker and area behind vent paler (1). No further information.
CRITICALLY ENDANGERED. Previously considered Vulnerable, then (2008) Endangered and more recently uplisted to highest threat category, while a single species action plan has been prepared as a result (6). Population most recently estimated by BirdLife International at just 150–700 mature individuals and considered to be still declining. Wide range (c. 1,640,000 km²) but always rather rare in recent decades, although in first quarter of 20th century was still regarded as “extremely abundant” on passage through Hebei (NE China) (18). Survey of 40 known localities in China, especially in lower and central Yangtze floodplain, in winter 2012/13 revealed total of just 45 birds, with possibility of some duplication, and none at all was seen during same period in Bangladesh and Myanmar (19). However, 84 birds were present at single site in Shandong province, China, in Dec 2014 (5), and total of 238 individuals were recorded that winter, the vast majority in China, with other records in NE India (Assam), Myanmar and Philippines (6). Also, very few recent confirmed breeding records, e.g. in 2012 just one pair in C Hebei province and perhaps four pairs in Shandong province, with 7–8 pairs in first-named in spring 2015, both of which are S of the usual breeding range (19, 4), while in Far Eastern Russia there were no published breeding-season records in the Amur region between 1976 and 2012, although the species possibly bred at a private nature reserve there in 2013 (20). There have been recent (2013 and 2014) breeding-season records in North Korea (6). Sharp decline recently in former USSR linked to drainage for rice cultivation and increased disturbance, while elsewhere habitat degradation (e.g. drying up of relevant waterbodies in Xianghai Reserve and Baiquan wetlands in Wuhan) and hunting are speculated to be significant factors (although reports of potentially huge numbers being shot in Jiangsu Province, China, are probably erroneous), but causes are poorly understood. Captive duck ‘farming’ might be another negative factor; A. baeri have been observed at such sites, and in general many birds that are supposedly captive-bred originate from the wild, usually from eggs collected in the wild then hatched in captivity (19). Whatever the reasons, recent years have seen small numbers in many formerly important wintering areas, with just c. 10 individuals in last five years in Bangladesh (99% decline versus perhaps c. 2000 just 20 years ago, although some very large counts from this region have recently been questioned) (17), only 4–5 birds at Bung Boraphet (Thailand) and a marked range contraction in S China, with no records from many provinces in recent years, despite increases in birdwatching activity, including almost complete loss of populations along Yangtze R (where 630 recorded in early 2004) (21), at L Wuchang, Anhui (previously held largest-known concentration, of > 200 birds, in recent years), L Liangzi (c. 130 in winter 2010/2011) and Baiquan wetlands, Wuhan, while observations of migrants along Hebei coast have also been considerably reduced. Now very rare in both Vietnam and Nepal in recent winters. In late 1980s and early 1990s significant numbers still recorded in Vietnam (40 near Hanoi) and especially Thailand, with some counts of over 100, and up to 426 in Beung Boraphet, Nakhon Sawan Province; in China too, with 100 or more recorded at several sites, and notable 750 birds counted in 23 localities in Yancheng Marshes, coastal Jiangsu Province, in Jan 1988 (with 414 there in 2001) (22), while partial census in winter 1990 yielded: 575 in India; 10 in Bangladesh; 90 in Burma; 192 in Thailand; 853 in China. Some breeding and wintering sites lie within protected areas, including Daursky, L Khanka and L Bolon (Russia), Sanjiang and Xianghai (China), Mai Po (Hong Kong), Koshi Barrage (Nepal), Kaziranga National Park (Assam, India) (23) and Thale Noi (Thailand). Approximately 200 birds are currently in captivity, of which c. 70 have been genetically sampled and studbooks are planned, given the probability that captive breeding may be required in the species’ future conservation (6).