Scaly-sided Merganser Mergus squamatus Scientific name definitions

52–62 cm; male 1125–1400 g, female 870–1100 g (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ); wingspan 70–86 cm (2 Brazil, M. (2009). Field Guide to the Birds of East Asia: Eastern China, Taiwan, Korea, Japan and Eastern Russia. Christopher Helm, London, UK. Close ). Structurally intermediate between M. merganser and M. serrator. Male in breeding plumage has head, neck and scapulars black glossed green, with long drooping double crest , white breast, underparts  and mantle (flanks and back finely scaled black), white rump and uppertail with fine dark grey vermiculations, and tail silvery grey; eclipse plumage resembles that of adult female, but retains black scapulars and more extensive white wing-coverts (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). Female has grey mantle and upperwing, white throat and breast, brown head and neck (with long wispy crest  and noticeably darker lores) and grey-scaled white flanks , although some females may have more uniform, unmarked white flanks; patterning on sides and flanks differentiates female from that of M. merganser and other species of Mergus. Bare parts: bill long, thick and bright red with yellow tip, irides dark brown, and tarsi reddish orange (2 Brazil, M. (2009). Field Guide to the Birds of East Asia: Eastern China, Taiwan, Korea, Japan and Eastern Russia. Christopher Helm, London, UK. Close ). In flight, wing pattern is like that of M. serrator, but male has large white patch divided by two fine black lines, while female has smaller patch divided by single black line (2 Brazil, M. (2009). Field Guide to the Birds of East Asia: Eastern China, Taiwan, Korea, Japan and Eastern Russia. Christopher Helm, London, UK. Close ). Juvenile largely similar to female, but has relatively darker head and upperparts with less extensive pale flanks scaling and has pale buffish-white crescent below eye and line from bill to eye (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ); young male separable from juvenile female by paler upperwing-coverts (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ).

Breeds in extreme SE Siberia, NE China and N Korea. Winters mainly in C & S China (especially in R Yangtze catchment); also in SE Russia, Korea, Japan, occasionally Taiwan, Myanmar and Thailand.

During breeding season, inhabits well-forested, clear, fast-flowing mountain rivers and rapid streams with many shingle spits and islands, in taiga zone; typically far from human habitation, in Russia woodland is characterized by white-barked elm (Ulmus propinqua), black pine (Pinus koraiensis), lime (Tilia amurensis) and Maximovitch poplar (Populus maximoviczii), but in China by Daimyo oak (Quercus dentata), black pine, lime and Linden poplar (Populus ussuriensis), always with dense undergrowth (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). Previously thought to winter mainly on lakes, reservoirs (2 Brazil, M. (2009). Field Guide to the Birds of East Asia: Eastern China, Taiwan, Korea, Japan and Eastern Russia. Christopher Helm, London, UK. Close ), more sluggish rivers and lagoons, but recent winter records, both in China and Korea, have mostly been from clear fast-flowing rivers in hilly and mountainous areas, with low disturbance levels (4 Barter, M., Zhuang, X., Wang, X., Cao, L., Lei, J., Solovyeva, D. and Fox, A.D. (2014). Abundance and distribution of wintering Scaly-sided Mergansers Mergus squamatus in China: where are the missing birds? Bird Conservation International. 24: 406–415. Close ). A small percentage of the population, however, undertakes moult migration to brackish and marine waters, as revealed both by stable isotopes and geolocators (5 Solovyeva, D., Newton, J., Hobson, K., Fox, J.W., Afanasyev, V. and Fox, A.D. (2014). Marine moult migration of the freshwater Scaly-sided Merganser Mergus squamatus revealed by stable isotopes and geolocators. Ibis. 156(2): 466–471. Close ).

Migratory (though true extent still not entirely known), mainly present on breeding grounds between late Mar/Apr (occasionally early Mar) (6 Zhao Zhengjie and Pao Zhengjie (1998). The foraging behaviour of the Scaly-sided Merganser Mergus squamatus in the Changbai Mountains and Xiao Xingangling Mountains of China. Forktail. 14: 76–77. Close ) and late Sept/late Oct (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ), exceptionally early Nov (5 Solovyeva, D., Newton, J., Hobson, K., Fox, J.W., Afanasyev, V. and Fox, A.D. (2014). Marine moult migration of the freshwater Scaly-sided Merganser Mergus squamatus revealed by stable isotopes and geolocators. Ibis. 156(2): 466–471. Close ); moulting birds (mainly males) congregate from early Jun on upper reaches of breeding rivers (e.g. Bikan and Iman, in Russia, and Toudaibai, Sandaobai, Mang and Gutong, in China) and on coasts of Seas of Japan and Okhotsk (latter perhaps especially males, non-breeding and failed females) (5 Solovyeva, D., Newton, J., Hobson, K., Fox, J.W., Afanasyev, V. and Fox, A.D. (2014). Marine moult migration of the freshwater Scaly-sided Merganser Mergus squamatus revealed by stable isotopes and geolocators. Ibis. 156(2): 466–471. Close ), then moves S, when recorded on migration at L Khanka on Russo-Chinese borders, on L Jingpo and L Xiaobei, in NE Heilongjiang Province (China), and on Chogchon R (North Korea) (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ); females and juveniles depart breeding areas much later, generally between mid Sept and third week of Oct (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ), and moulting areas of males and females may differ, even when both use freshwater localities (5 Solovyeva, D., Newton, J., Hobson, K., Fox, J.W., Afanasyev, V. and Fox, A.D. (2014). Marine moult migration of the freshwater Scaly-sided Merganser Mergus squamatus revealed by stable isotopes and geolocators. Ibis. 156(2): 466–471. Close ). Main wintering sites, which are presumed to be in S & C China, are basically unknown, although surveys of c. 1000 km of rivers and 11 reservoirs in SE China in winters of 2006 and 2008 found 71 individuals (31 (8 Barter, M., L. Cao, L. Chen, and G. Lei (2005). Results of a survey for waterbirds in the lower Yangtze floodplain, China, in January–February 2004. Forktail 21:1–7. Close ) and 40 respectively), with birds at four sites in NE Jiangxi during 2002–2007 including peak of 88 on 22-km stretch of Xinjiang R (where c. 100 at Poyang Hu in winter 1999) (9 Rank, M. (2000). New populations of mergansers, cranes and bustards. Bull. Oriental Bird Club. 32: 31. Close ), but wide scatter of records at this season from provinces of Liaoning (indicating that species can remain far N in winter), Qinghai, Gansu, Ningxia, Sichuan, Yunnan (once as late as May), Guizhou, Shandong, Hubei, Anhui, Jiangsu (including Yancheng Nature Reserve, where up to 22 recorded) (10 Benstead, P. (2002). Conservation Fund: The conservation of threatened birds and their habitats at Yancheng marshes, Jiangsu, China. Bull. Oriental Bird Club. 36: 13. Close ), Shanghai, Zhejiang, Fujian, Jiangxi, Hunan, Guangxi (11 Jiang, A., F. Zhou, and N. Liu (2014). Significant recent ornithological records from the limestone area of south-west Guangxi, south China, 2004–2012. Forktail 30:122–129. Close ) and Guangdong (as late as Apr) (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ). A female ringed on Kievka R, S Primorye (Russia) in May 2012 was photographed in China’s Hunnan province in Dec 2012  , providing the first direct evidence of the scale of the species’ migratory tendencies (12 Zeng, Q., Zhang, J., Li, H., Lu, K. and Lei, G. (2013). The first record of a ringed Scaly-sided Merganser Mergus squammatus at a wintering site in southern China. BirdingASIA. 19: 57–58. Close ). At this season, has also occurred in Japan (first record as recently as Dec 1987, in C Honshu (13 Brazil, M. (1991). The Birds of Japan. Christopher Helm, London, UK. Close ), typically between Nov and Mar, occasionally until Apr) (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ), Taiwan (first record 1981, sometimes until Apr) (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ), N Vietnam (W & E Tonkin (14 Robson, C. (2000). A Field Guide to the Birds of South-east Asia. New Holland, London, UK. Close ), in 1915 and Dec 1926) (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ), NW Thailand (Jan–Feb 1991) (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ), N Burma (undated) (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ) and Tibet (Jan 1929) (15 Vaurie, C. (1972). Tibet and its Birds. H. F. & G. Witherby, London, UK. Close ). Two birds were recently satellite-tracked from their breeding grounds at Dailing in SE Lesser Xingan Mts of China. Both crossed the Yellow Sea and travelled 2600 km to winter on the Yuanjiang R (Hunan) and Xiushui R (Jiangxi) further S in China. The Ryonghung Gang estuary in North Korea, Yunshui R and Chidong L in Hubei, China, and Songjiang R, in Jilin, China, constituted important stopover sites (16 Liu Dong-Ping, Li Cheng-Quan, Zhang Guo-Gang, Lu Jun and Chen Gang. (2014). Satellite tracking of Scaly-sided Merganser (Mergus squamatus) breeding in Lesser Xingan Mountains, China. Waterbirds. 37(4): 432–438. Close ).

Until recently few data available, but several studies have now elucidated the species’ diet and foraging behaviour. Diurnal feeder, taking mainly small fish and aquatic invertebrates (e.g. Gaidrosparius and Trichoptera larvae) (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ), opportunistically selecting most abundant potential prey according to habitat, season and distribution (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). In SE Russia eight main fish prey species identified—Amur minnow (Phoxinus lagowskii), grayling (Thymallus arcticus grubei), lenok (Brachymystax lenok), gudgeon (Gobio gobio), trout (Salmoninae), northern pike (Esox lucius), chebak (Leuciscus schmidti) and weather loach (Misgurnus anguillicaudatus)—but diet also includes Masu salmon (Oncorhyncus masou), Dolly Varden char (Salvelinus malma), stone loach (Nemachilus barbatulus), spotted sculpin (Cottus poecilopus) and chub (Leuciscus brandtii), and at relevant times has also been observed to make twice daily (morning and evening) trips to river mouths to feed on spawning smelt (Osmerus eperlanus dentex), pond smelt (Hypomesus olidus) and capelin (Mallotus) (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). In NE China, during breeding season, takes stonefly and caddis fly larvae, beetles, shrimps, crayfish, lamprey (Lampetra morii), loach, lenok, Amur sculpin (Mesocottus haitej) and grayling; predominantly (90%) takes caddis fly larvae during Jun–Jul, switching to small fish, shrimps and crayfish in Aug, then fish fry in Sept (6 Zhao Zhengjie and Pao Zhengjie (1998). The foraging behaviour of the Scaly-sided Merganser Mergus squamatus in the Changbai Mountains and Xiao Xingangling Mountains of China. Forktail. 14: 76–77. Close ). Feeds mainly by diving , each dive lasting c. 15–30 seconds with inter-dive intervals of 3–5 seconds, but in shallow water also forages by immersing head alone; on breeding rivers, feeds mostly close to bank, in shallow water (< 1 m deep) (6 Zhao Zhengjie and Pao Zhengjie (1998). The foraging behaviour of the Scaly-sided Merganser Mergus squamatus in the Changbai Mountains and Xiao Xingangling Mountains of China. Forktail. 14: 76–77. Close ). Study in NE China found that during breeding season bird may spend 14–15 hours/day feeding (between 03.00 hours and 18.00–19.00 hours) (6 Zhao Zhengjie and Pao Zhengjie (1998). The foraging behaviour of the Scaly-sided Merganser Mergus squamatus in the Changbai Mountains and Xiao Xingangling Mountains of China. Forktail. 14: 76–77. Close ). In non-breeding season may occur alongside and compete for food with other diving ducks such as M. merganser, M. serrator, Bucephala clangula, etc. (6 Zhao Zhengjie and Pao Zhengjie (1998). The foraging behaviour of the Scaly-sided Merganser Mergus squamatus in the Changbai Mountains and Xiao Xingangling Mountains of China. Forktail. 14: 76–77. Close ) Usually encountered in small groups of 3–5 (17 Zhiao Zhengjie, Xiaodong Han, Shuhua Zhang, Jinggai Wu and Zhengji Piao (1995). Breeding ecology of the Chinese Merganser in the Changbai Mountains, China. J. Field Orn.. 66(1): 54–59. Close ), later in in breeding season 6–10 individuals (6 Zhao Zhengjie and Pao Zhengjie (1998). The foraging behaviour of the Scaly-sided Merganser Mergus squamatus in the Changbai Mountains and Xiao Xingangling Mountains of China. Forktail. 14: 76–77. Close ), but males form flocks of 10–25 immediately before moving to moulting areas and loose band of 76 recorded during autumn migration (Sept 1997) (9 Rank, M. (2000). New populations of mergansers, cranes and bustards. Bull. Oriental Bird Club. 32: 31. Close ).

Generally silent (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ) but vocalizations much like those of M. serrator, though also makes deep, hoarse hiss (2 Brazil, M. (2009). Field Guide to the Birds of East Asia: Eastern China, Taiwan, Korea, Japan and Eastern Russia. Christopher Helm, London, UK. Close ). Female gives deep “kreck” alarm call, similar to that of M. merganser but less harsh and quieter, and both sexes utter quieter versions in social interaction and courtship; when leading young away from nest, female gives muffled, murmuring, cooing “krr-krr-krr-krr-krr” (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ).

Little known until recently. During local spring: arrives on breeding grounds late Mar/early Apr, initially frequents lakes and larger rivers then moves to smaller tributaries (17 Zhiao Zhengjie, Xiaodong Han, Shuhua Zhang, Jinggai Wu and Zhengji Piao (1995). Breeding ecology of the Chinese Merganser in the Changbai Mountains, China. J. Field Orn.. 66(1): 54–59. Close ), with most eggs laid between first week and end of Apr, with most hatching in Jun (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ) (exceptionally as early as mid May) (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ). Monogamous. In single pairs, which are highly territorial, with both sexes defending c. 200–300 m area around nest against conspecifics, M. merganser and Carrion Crows (Corvus corone) (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ); wider home range varies from 500–600 m (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ) stretch of river to 2–8 km (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ). Nests in tree hollows 1·5–18 m above ground (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ), typically in riverbank poplar, elm, oak, etc., but sometimes sited up to 120 m from watercourse; nest-hole (sometimes adopted from other mergansers or Oriental Scops-owl Otus sunia) typically 9–25 cm wide by 11–60 cm tall, while hollow within is 20–30 cm in diameter and 40–120 cm deep; lined with pale grey down and dry grass (17 Zhiao Zhengjie, Xiaodong Han, Shuhua Zhang, Jinggai Wu and Zhengji Piao (1995). Breeding ecology of the Chinese Merganser in the Changbai Mountains, China. J. Field Orn.. 66(1): 54–59. Close ); can be site-faithful, especially if previous nesting attempt successful (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ), for up to three years at least (17 Zhiao Zhengjie, Xiaodong Han, Shuhua Zhang, Jinggai Wu and Zhengji Piao (1995). Breeding ecology of the Chinese Merganser in the Changbai Mountains, China. J. Field Orn.. 66(1): 54–59. Close ). Readily accepts nestboxes, and may nest in relatively close proximity to roads or habitation (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). Single-brooded, but will renest if first clutch lost early in season (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). Clutch usually 10–11 eggs (range 4–14) (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ), creamy white, size 56·7–67·5 mm × 42·8–46·8 mm, laid at 36–hour intervals (thus over 15–16-day period); incubation c. 32 days (31–35 days) (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ), by female alone, usually with twice-daily recesses (in early morning and late afternoon) or single off-bout (around midday) and total time away from nest declining during incubation period from c. 50–95 minutes daily to no more than c. 20 minutes (may not leave nest at all during final 1–2 days) (17 Zhiao Zhengjie, Xiaodong Han, Shuhua Zhang, Jinggai Wu and Zhengji Piao (1995). Breeding ecology of the Chinese Merganser in the Changbai Mountains, China. J. Field Orn.. 66(1): 54–59. Close ); newly hatched duckling weighs 31·3–45 g, and has reddish-brown crown and upper cheeks, ash-grey upperparts and white underparts, with white lores, spot above eye and crescent below it, bill dark brown and legs and feet slate-grey (17 Zhiao Zhengjie, Xiaodong Han, Shuhua Zhang, Jinggai Wu and Zhengji Piao (1995). Breeding ecology of the Chinese Merganser in the Changbai Mountains, China. J. Field Orn.. 66(1): 54–59. Close ); leaves nest in early morning (encouraged to do so by calling female) 48–60 hours after hatching (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ), following which brood amalgamation is common (single females regularly seen with 20–30 ducklings, exceptionally up to 48) (7 Collar, N. J., A. V. Andreev, S. Chan, M. J. Crosby, S. Subramanya, and J. A. Tobias, Editors (2001). Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Close ); fledging occurs at c. 8 weeks (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). Hatching success in Chinese study varied from 85% to 100%, with fledging success of five broods complete (17 Zhiao Zhengjie, Xiaodong Han, Shuhua Zhang, Jinggai Wu and Zhengji Piao (1995). Breeding ecology of the Chinese Merganser in the Changbai Mountains, China. J. Field Orn.. 66(1): 54–59. Close ). Mean brood sizes of 9·8 (at fledging), but elsewhere 7·1–8 (in Jun, at hatching), 4·7–6·2 (Jul) and seven (Aug), give some idea of mortality rates (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). Sexual maturity in females during third year of life (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ).

ENDANGERED. Fully protected in all range states (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). Poorly known, population probably quite small, but has been suggested that perhaps as many as 10,000 individuals survive, although BirdLife International precautionarily considers the overall population to currently number 2400–4500 mature individuals External link . A recent estimate put the global population at c.1940 pairs (or c. 4660 birds ): the current breeding range comprises c. 1800 km of 120 rivers: 6800 km in Russia, 600 km in China and 400 km in North Korea. In Russia it comprises 88 rivers on both W & E slopes of Sikhote-Alin Range, and two small isolated areas, one in C Khabarovsk and the other in the Jewish Autonomous Oblast. In China the breeding range comprises the W slope of Changbai Mts, and (formerly) an isolated river system in the Lesser Xingan Mts. Scaly-sided Mergansers are also assumed to breed on E slope of Changbai Mts in North Korea (18 Solovyeva, D.V., Liu, P., Antonov, A.I., Averin, A.A., Pronkevich, V.V., Shokhrin, V.P., Vartanyan, S.L. and Cranswick, P.A. (2014). The population size and breeding range of the Scaly-sided Merganser Mergus squamatus. Bird Conservation International. 24(3): 393–405. Close ). In Russian Far East, maximum population estimate in Primorskii Krai , one of main breeding areas, c. 1000 breeding pairs (19 Mikhailov, K.E. and Shibnev, Y.B. (1998). The threatened and near-threatened birds of northern Ussuriland, south-east Russia, and the role of the Bikin River basin in their conservation. Bird Conservation International. 8(2): 141–171. Close ); in early 1980s, estimated 482 birds along 3000 km stretch of R Bikin, where intense hunting (around 100 taken annually); one pair, at most, seen every 3·8 km² in Lazovsk protection area, and along Kievka Valley, but recent surveys reveal that breeding density in Primorye has more than doubled since 1960s/1970s, and total of 173 individuals recorded along a 20-km stretch of R Iman in 2003 External link ; main breeding site was R Iman (19 Mikhailov, K.E. and Shibnev, Y.B. (1998). The threatened and near-threatened birds of northern Ussuriland, south-east Russia, and the role of the Bikin River basin in their conservation. Bird Conservation International. 8(2): 141–171. Close ), threatened by high levels of disturbance (commercial logging, timber and pleasure rafting), silting of rivers, pollution (gold mining) and drowning in fishing nets (up to 20% of young die in this way in Sikhote-Alin Mts) (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). M. merganser (in particular, as currently expanding in range) (19 Mikhailov, K.E. and Shibnev, Y.B. (1998). The threatened and near-threatened birds of northern Ussuriland, south-east Russia, and the role of the Bikin River basin in their conservation. Bird Conservation International. 8(2): 141–171. Close ) and perhaps Aix galericulata may compete for nest-sites (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). In Khabarovsk region, c. 100 pairs estimated in 1981. Records indicate that Russian population suffered drastic decline since 1960s/70s—having disappeared from some regions and in others just 10% or even 5% of former estimated numbers remain—but apparently increasing again or stable during last decade. In Chonpaek Mts, NE China, mean 3·6 birds per 5 km of river and in Chingbai Mts recent breeding density of 0·26 ± 0·3 pairs per km (20 Liu, P., Li, F., Song, H., Wang, Q., Song, Y., Liu, Y. and Piao, Z. (2010). A survey to the distribution of the Scaly-sided Merganser (Mergus squamatus) in Changbai Mountain range (China side). Chinese Birds. 1(2): 148–155. Close ) (versus densities of 0·4–3·8 pairs per 10 km in Russia) (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ); Chinese breeding population estimated at 200–250 pairs (21 Zhao Zhengjie (1998). Scaly-sided Merganser will be faced with the threat of extinction. Ostrich. P. 464 in:. Close ) and is declining, with recent surveys of 1553 km along four rivers in Chingbai Mts suggesting population of 170 pairs in 2008–2009 (20 Liu, P., Li, F., Song, H., Wang, Q., Song, Y., Liu, Y. and Piao, Z. (2010). A survey to the distribution of the Scaly-sided Merganser (Mergus squamatus) in Changbai Mountain range (China side). Chinese Birds. 1(2): 148–155. Close ) (following virtual extinction in Xingan Mts, where 30–40 pairs in 1994–1995 (22 Zhao Zhengjie (1995). Scaly-sided Merganser in Xiao Xingangling mountains, China. Bull. Oriental Bird Club. 22: 13–14. Close ), and Wusuli basin). Using a Species Distribution Model, the wintering population in China has been estimated at 3561 ± 478 individuals (in 2010–2012) (23 Zeng, Q., Zhang, Y., Sun, G., Duo, H., Wen, L. and Lei, G. (2015). Using Species Distribution Model to estimate the wintering population size of the endangered Scaly-sided Merganser in China. PLOS One. 10(2): e0117307. Close ).< In North Korea, probably breeds around Mayang Chosuji, where a pair apparently displaying was observed in 1986, and more recently was suggested that perhaps up to 200 pairs breed there; the area is protected, and fishing and tree felling prohibited. Throughout most of range, projects for construction of dams, felling of old hollow trees, disturbance of rivers by lumber carrying motorboats and possibly predation by feral American mink (Mustela vison) pose additional threats, while the low levels of genetic diversity recently found in this species might represent an additional source for concern (24 Solovyeva, D.V. and Pearce, J.M. (2011). Comparative mitochondrial genetics of North American and Eurasian mergansers with an emphasis on the endangered scaly-sided merganser (Mergus squamatus). Conservation Genetics. 12(3): 839–844. Close ). Original decline in Russia coincided with economic development of taiga, but large-scale deforestation of river valleys is now prohibited, although new Russian Forest Codex (2007) probably insufficiently robust and it is likely that suitable breeding habitat for this species will continue to decrease. Logging of river sources and adjacent slopes has led to reduced spring water levels and changes in fish abundance; since logging began on the Avvakumovka R in 2004, spring water levels and merganser populations have undergone continuous declines. Other major threats within breeding range include increased sport hunting of waterfowl together with poor regulation of spring hunting season (intended to coincide with passage migration and avoid targeting locally breeding birds); large numbers of mergansers were reportedly shot in Kievka R basin, S Primorye, in spring 2008. In China, fine-mesh fishing nets were significant threat to post-breeding congregations at Song Jiang He in Jilin Province, but illegal fishing has been reduced and only large-meshed nets are used in legal fish-farming. but this site remains threatened by industrial pollution. Proposed Korean Grand Canal project, which aimed to canalize 3134 km of Peninsula’s rivers and radically alter Han and Nakdong rivers (which currently support c. 30–50 birds in winter), was suspended Jun 2008 (25 Moores, N. (2008). The Korean Grand Canal: another huge threat to the region’s wetlands and waterbirds. BirdingASIA. 10: 48–53. Close ), and the alternative Four Rivers Project was proposed instead and commenced in 2009 (26 Moores, N., Kim, A., Park, M.-N., Kim, S.-A. (2010). The Anticipated Impacts of the Four Rivers Project (ROK) on Waterbirds: Preliminary Report. Birds Korea, Seoul. Close ). In South Korea , species impacted by increased river turbidity due to construction and dredging, bridge-building activities, riverbank strengthening and road-widening schemes (26 Moores, N., Kim, A., Park, M.-N., Kim, S.-A. (2010). The Anticipated Impacts of the Four Rivers Project (ROK) on Waterbirds: Preliminary Report. Birds Korea, Seoul. Close ). Some of these are associated with Four Rivers Project on stretches of river used by mergansers, while rivers will also be deepened and boulders and islands (which are used for roosting) will be removed, thus rendering many areas unusable (26 Moores, N., Kim, A., Park, M.-N., Kim, S.-A. (2010). The Anticipated Impacts of the Four Rivers Project (ROK) on Waterbirds: Preliminary Report. Birds Korea, Seoul. Close ). In China, explosives and poison used by fishermen must also be considered threats (22 Zhao Zhengjie (1995). Scaly-sided Merganser in Xiao Xingangling mountains, China. Bull. Oriental Bird Club. 22: 13–14. Close ). Small parts of the species’ breeding and non-breeding populations occur in protected areas, notably Sikhote-Alin State Biosphere Reserve, Lazovskiy State Reserve and Botchinskiy State Reserve (Russia), and Changbai Shan Nature Reserve (China). An artificial nest programme in Russia, involving provision of at least 180 nestboxes (27 Cranswick, P. (2010). Conservation of the Scaly-sided Merganser in Far East Russia. WWT Conserv. Rep.. 2008–2009: 33. Close ), has shown positive results (the 1000th duckling hatched in 2015) (28 Ławicki, Ł., and A. B. van den Berg (2015). WP reports. Dutch Birding 37(5):340–353. Close ), increasing habitat capacity along rivers with logged floodplains, involving continued maintenance of artificial nests, liaison with hunters and fishers and collaboration with local communities, which has already led to change in fishing practices by local people and has facilitated the capture of females for tagging with geolocators, allowing identification of staging and wintering sites (27 Cranswick, P. (2010). Conservation of the Scaly-sided Merganser in Far East Russia. WWT Conserv. Rep.. 2008–2009: 33. Close ). Nestboxes have also finally been used successfully in China too (28 Ławicki, Ł., and A. B. van den Berg (2015). WP reports. Dutch Birding 37(5):340–353. Close ).