133

Scaly-sided Mergansers Mergus squamatus on the lower , central J.W. Duckworth1 & Kim Chol2

1East Redham Farm, Pilning, Bristol BS35 4JG, UK. Email: [email protected] 2Eco-environment Research Unit, Environment and Development Centre, Gwangbok-dong, Mangyongdae District, , DPR Korea.

In autumn 2003, the lower Chongchon River in central Korea supported at least 40 Scaly-sided Mergansers Mergus squamatus, significantly exceeding previous published estimates of the DPR Korean population. This is a non-breeding concentration of global significance (on currently available information) for this threatened species. Information is presented upon numbers present, sex ratio and behaviour from mid-October (when the birds were found) until late November (when observations ceased). Supplementary observations from March 2004 and autumn 2004, indicating regular use of the site, are also presented. Conservation issues related to the species at the site are reviewed.

Key Words: threatened species, discovery, conservation, moult, human disturbance

© Wildfowl & Wetlands Trust Wildfowl (2005) 55: 135-144 134 Scaly-sided Mergansers in central Korea

Introduction no dates or numbers) from the lower Orangchon River and Lake Samjiyon The Scaly-sided Merganser Mergus (Austin 1948; BirdLife International squamatus breeds only in parts of the 2001; Chong & Morishita 1996; Fiebig Russian Far East, northeast China and 1993–1995; MKN & KUT 1987; Tomek northern Korea and winters across a 1999–2002; Won Hong Koo 1963). These much larger area of central and eastern areas all lie in the northernmost two China, and reportedly within the provinces of Korea, Hamgyong North breeding range in the Russian Far East. and Ryanggang. A study Museum of Smaller numbers of non-breeders visit Korean Nature and Korea University in Japan, Taiwan and southern Korea, Tokyo (1987) (hereafter referenced as with a few records from Southeast Asia MKN & KUT) implied that the species (BirdLife International 2001; Chong & also occurs in ; the Morishita 1996; Delacour & Jabouille Amnok River, which forms the border 1931; Delacour et al. 1928; He Fen-Qi et between Korea (Chagang) and China, al. 2002; Hughes & Hunter 1994; Round is, in its middle and lower reaches, & Verbelen 1997). With evidence from an important wintering area for the both China and Russia of significant species (Zhao Zhengjie et al. 1994b). declines (Bocharnikov & Shibnev 1994; Records from southern Korea so far Jia Shaobo et al. 2003; Mikhailov & indicate a small wintering population, Shibnev 1998; Zhao Zhengjie et al. and MKN & KUT (1987) stated that the 1994a), the species is internationally species is ‘extremely rare’ in northern red-listed as Globally Threatened: Korea; but BirdLife International (2001, Endangered (Threatened Waterfowl p. 532) speculated that it may prove to Specialist Group 2003), although, at have been under-recorded across the least in parts of Russia, the population peninsula. Indeed, the known global is now increasing, perhaps substantially population outside the breeding season (Shokhrin & Solovieva 2003). This may cannot account for the known number of reflect the cessation of timber-rafting breeders (BirdLife International 2001; (see Surmach & Zaykin 1994). BirdLife He Fen-Qi et al. 2002), so undiscovered International (2001) estimated the total wintering and passage areas must population to be below 4,000 birds, exist. although Shokhrin & Solovieva (2003) speculated that it may exceed 10,000. Methods Bird survey work in northern Korea has been limited (Tomek 1999–2002) During autumn 2003, Scaly-sided and there are only a few internationally Mergansers were recorded on nine published records of Scaly-sided days on the lower Chongchon River, Merganser: two at Musan on 16 April Pyongan North – Pyongan South 1912, one at Janghungri on 29 March Provinces (c. 39°40’ N, 125°40’ E – 1958, and three birds at Mayang 40°02’ N, 126°12’ E), while the authors Reservoir in May 1986 and 20 September were driving between Pyongyang and 1989, where breeders are said to arrive the town of Hyangsan (Table 1). The in April. There are also reports (but road crosses the Chongchon near its Scaly-sided Mergansers in central Korea 135

Table 1: Sightings of Scaly-sided Mergansers on the Chongchon River, central Korea, autumn 2003, March 2004 and autumn 2004. Number of Date Location* Notes birds§ 2003 15 Oct 24 km 22 (2:20) 28 Oct 15 km 36 (3:33) 31 Oct 7 km 28 (4:24) 4 Nov 38 km 12 (2:10) Flushed upstream, distance unclear. 4 Nov 15 km 9 (2:7) Assumed different group from above. 12 Nov 41 km 12 (4:8) 2:4 of them flushed upstream, distance unclear. 12 Nov 15 km 6 (1:5) Assumed different group from above. 14 Nov 41 km 8 (2:6) 19 Nov 41 km 10 (3:7) Not flushed. 19 Nov 15 km 14 (4:10) Assumed different group from above. 24 Nov 41 km 4 (1:3) Flushed upstream, probably soon settled. 24 Nov 36 km 7 (1:6) Assumed different group from above; not flushed. 24 Nov 16 km 4 (1:3) Assumed different from above; loafing, seemed well settled. 24 Nov 14 km 1 (0:1) Certainly different from group 2-km distant. 26 Nov 24 km 3 (1:2) 2004 11 Mar 11 km 9 (3:6) 15 Mar 32 km 2 (1:1) Not flushed. 15 Mar 20 km 2 (1:1) Assumed different pair from above. 15 Mar 14 km 11 (6:5) Assumed different group from above two. 20 Mar 41 km 2 (1:1) Flying downstream, very low over water. 20 Mar 16 km 2 (1:1) Soon after above pair, and assumed different. 20 Mar 14 km 6 (3:3) Certainly different from above pair. 28 Oct 43 km 14 (4:10) 28 Oct 40 km 4 (0:4) Perhaps forming one dispersed flock with the above. 28 Oct 15 km 2 (0:2) Assumed different from above birds. 4 Nov 45 km 8 (2:6) 4 Nov 41 km 8 (0:8) Certainly different from above birds. 4 Nov 40 km 1 (0:1) Perhaps straggled individual from above flock. 4 Nov 26 km 2 (1:1) Certainly different from above birds. 4 Nov 16 km 4 (2:2) Certainly different from above birds.

Notes: *Location figures are distances from Hyangsan according to road signs, and include the 2 km from where the road leaves the river and runs directly into Hyangsan town. §The number of birds is given as ‘total number (number of adult males: number of redheads)’. An adult is in its second winter or older; a redhead is a female or first-winter male. 136 Scaly-sided Mergansers in central Korea mouth (at the Anju bridge), and 70 km unlikely that large numbers winter on south of Hyangsan, but the river cannot the Chongchon because the unfrozen be seen from the road until 45 (road) stretches do not exceed 200 m across: km south of Hyangsan. Scaly-sided although the Amnok River supports Mergansers were found the length of wintering birds and is significantly to this stretch, which lies largely in Gujang the north, lengthy stretches do not County; the upper few kilometres are freeze because power station discharge in , and the lower warms the water. few in Yongbyon County. The length of A visit in March 2004 again found the river is about 10–20% more than Scaly-sided Mergansers on this stretch the length of the road, because of of the Chongchon. On 3 March, most of meanders. Effectiveness of coverage the river was still frozen over, and the was calculated by estimating, for open stretches supported many people. each half-kilometre of road, whether No ducks were seen. By 11 March, a typical group of mergansers would almost all the ice had melted, and have been detected on all (score 3), > Scaly-sided Mergansers were found half (score 2), < half (score 1) or none then and on both subsequent journeys (score 0) of the adjacent water surface. (Tables 1 and 3). As in autumn, birds Only half the river (score 135, of a used almost the length of the surveyed maximum of 270) was estimated to be river, but total counts were lower in view when driving towards Hyangsan, (no overlap: autumn minimum 16, and about an eighth when returning. spring maximum 15). It is unlikely that The totals in Table 2 hence presumably birds were present in any significant underestimate the total population on numbers, if at all, along this section of this stretch of the Chongchon River. the Chongchon during May–July 2003 and September 2003, because the Results and Discussion river was checked frequently during these months (for Mandarin Ducks Aix At least 40 birds used the river during galericulata) and no mergansers were the autumn: the maximum count of adult found. males was seven, and of ‘redheads’ Although there was no clear trend (females and first-winter males), 33 in total number of birds present across (Table 2). The date of first sighting, the autumn, a directional change in 15 October, might not indicate arrival, sex ratio (increase in proportion of because the journey that the authors adult males) suggested a changing made the previous week (7 October) population and hence probably a was made in the dark. The last journey total number of birds exceeding was made on 26 November, and Scaly- the minimum of 40. The increase sided Mergansers were still present. in observed males did not reflect Indeed, they might winter at the site: completion of moult; all adult males although almost all the river is iced were in full breeding plumage even in over from mid-December to February, mid-October, which accords with data small patches in the fast-flowing in Kolomiitsev (1995). In October, each freshwater reaches remain open. It is day’s sightings involved only a single Scaly-sided Mergansers in central Korea 137 3 1 3 1 24 33 >Py 26 Nov Hy),onlyanbut > 4 4 3 9 16 19 >Hy 24 Nov 2 7 41 12 13 24 >Hy 19 Nov 19 8 1 8 2 0 25 >Py 14 Nov 14 2 9 7 7 18 28 >Hy 12 Nov 12 2 4 3 19 21 10.5 >Hy 4 Nov 1 4 0 14 28 28 >Py 31 Oct31 1 3 8 0 36 36 Py).Figures from thelatter areitalics, in because counts (number individuals,of malesof >Hy 28 Oct > - - 0 0 0 0 >Hy 22 Oct 1 2 9 0 22 22 >Hy 15 Oct15 - - 0 0 0 0 >Hy 29 Sep 5 4 7 1 3 2 6 Total Mm: Total count of Goosanders over the same stretch of river. Total of Scaly-sided Mergansers in adult male plumage. Total count of Scaly-sided Mergansers. Mean group size of Scaly-sided Mergansers. Number of groups of Scaly-sided Mergansers. Percentage of Scaly-sided Mergansers in adult male plumage. Directioncartravel.of Approximately riverhalfthe scanned canbe fromroadthewhen travelling fromPyongyang Hyangsanto ( Direction Total Mm Total eighthwhen travelling from Hyangsan Pyongyangto ( Total Ms Total andgroups)of are notcomparable with those from journeys Hyangsan.to They are included here because group sizes andsex ratio estimatespresumed are to be comparable. Table 2: SummaryTable counts of Scaly-sided Mergansers and Goosanders on the Chongchon central River, Korea, autumn 2003. Date Alldaylight trips from Pyongyang Hyangsanto areincluded from 29September (two weeks before thefirst observation Scaly-sidedof until 26 NovemberMerganser) (end of survey period). 1 2 3 4 5 6 7 n groups Mean g.s. male Total % male 138 Scaly-sided Mergansers in central Korea

Table 3: Summary counts of Scaly-sided Mergansers and Goosanders on the Chongchon River, central Korea, in 2004.

Date 3 Mar 11 Mar 15 Mar 20 Mar 28 Oct 4 Nov Direction1 >Hy >Py >Hy >Hy >Hy >Hy Total Ms2 0 9 15 10 20 23 n groups3 0 1 3 3 3 5 Mean g.s.4 - 9 5 3.3 6.7 4.6 Total male5 0 3 8 5 4 5 % male6 - 33 53 50 20 22 Total Mm7 0 3 7 3 3 4

All trips from Pyongyang to Hyangsan made in the daylight are included from 3 March (the first check) until 20 March (the last spring check), as are both the autumn 2004 trips. large flock, whereas in November up to Scaly-sided Mergansers are generally four, smaller, flocks were found per day believed to occur in highly dispersed (Table 2). In Russia, the largest flocks small groups (e.g. He Fen-Qi et al. (15–20) occur in October (Bocharnikov 2002; Zhao Zhengjie et al. 1994a). & Shibnev 1994). In the breeding The largest concentrations so far grounds in the Changbaishan of China, known are both in China: over 100 groups exceeding ten were only seen birds in winter along 10 km of the during migration (Zhao Zhengjie & Xinjiang River, northeastern Jiangxi Pao Zhengjie 1998). In spring (Tables Province; and up to 76 on migration 1 and 3), the proportion of males was (April and September) at Xiaobei Lake higher than in early autumn, birds (near Ning’an in the Chiangbaishan were more dispersed (three groups mountains), southeastern Heilongjiang on both journeys, typically 1–2 in early (He Fen-Qi et al. 2002; Li Wenfa et al. autumn), and mean group size was 1998). smaller than in autumn. Indeed most All Scaly-sided Mergansers were on (four of seven) groups consisted of stretches of river with many boulders pairs (seen only once in autumn), and and cobbles projecting from the water. even in the largest group found, 11 Water-surface width in these stretches birds, two pairs were clearly moving was generally 20–60 m, exceptionally somewhat separately from each other 100 m. There was no adjacent forest; and from the remaining seven birds. Zhao Zhengjie and Pao Zhengjie (1998) No trace, however, was seen of active also found birds to use “larger rivers courting. without wooded banks” from October A site total of 40, probably rather to March. Feeding birds were in fast more, is a significant non-breeding flowing water, usually with ‘white- concentration of this species (0.4–1% water’ around the patches of rocks. of the estimated world population), Birds interspersed periods of very especially because during winter active feeding in the rushing water with Scaly-sided Mergansers in central Korea 139 loafing on boulders (or, occasionally, & Zaykin 1994; Yelsukov 1994). Most small sandbars) or in nearby sheltered significant, however, is probably the water. Most of the Chongchon visible presence of humans engaging in in this stretch supports such habitat, numerous activities from the collection although some stretches have few of stones and sediment to recreation. It rocks awash (at typical water levels). is rare to be able to view a significant The concentration of records into only a (1+ km) length of river and not see few stretches (Table 1) probably relates people beside or in the water in several to the fact that towns, footbridges or localities; sometimes, hundreds are very heavy human bank-side activity in view. Such disturbance is evidently are found on other visible stretches not at high enough levels to prevent of the river, rather than indicating birds using the river, but does result particularly suitable water conditions. in numerous flushings. Disturbance, Goosanders M. merganser also often from motor boats, is regarded use this stretch of the Chongchon, in is a major problem in Russia for this smaller numbers than of Scaly-sided species (Mikhailov & Shibnev 1998; Mergansers in both autumn and spring Solovieva 2002), but such boats barely (Tables 2 and 3). The two species formed use the Chongchon. Birds are most mixed groups, although in flocks with unlikely to be shot, because gun usage several of both species present they is strictly controlled. Equally, because tended to segregate slightly. of firm guidelines it is unlikely that On the journeys made in the fishing with poisons or explosives following autumn on 28 October and threatens the birds on the Chongchon, 4 November 2004, 20 and 23 birds although it does in the nearby were recorded, respectively (Tables Changbaishan in China (Zhao Zhengjie 1 and 3). This suggests that birds et al. 1994a). Finally, habitat alteration occur regularly on the Chongchon through embankment and associated and that significant numbers winter at road building may be underway on undiscovered sites in Korea. It echoes a significant proportion of potential the recent prediction of Moores (2002) wintering rivers elsewhere (N. Moores, that “probably 30–50...winter most unpublished data), but there is no sign years” [in southern Korea], somewhat of this on the Chongchon. exceeding the published wintering These observations come from population in southern Korea (< 10, only two, consecutive, non-breeding BirdLife International 2001). seasons. It is a priority to assess Several factors may threaten Scaly- whether birds use the site annually sided Mergansers on the Chongchon. and, hence, merit site-specific River flow is controlled by a large conservation measures. Counts of barrage in Hyangsan, industry in some birds through the non-breeding season riverside towns means that pollution should be combined with investigations must be at least a risk, and gill-netting of potential on-site threat factors. is a common practice. Entanglement in Surveys should run from mid-, or fishing nets is a significant problem, in even early, September right through the Russian range at least (Surmach the winter and into April. It is also 140 Scaly-sided Mergansers in central Korea

to seek this species on other large Scaly-sided Merganser Mergus squamatus rivers in north and central Korea: most in the Bikin river basin, Far-east Russia. In: The Scaly-sided Merganser Mergus appear superficially similar to the squamatus in Russia and China, IWRB Chongchon in terms of habitat (Kim Threatened Waterfowl Specialist Group Chol, unpublished data). Special Publication No. 1, (eds. B. Hughes & It is also important to search J. Hunter), pp. 3-10. WWT, Slimbridge, UK. remaining forested rivers in north Chong Jong Ryol & Morishita, T. 1996. Report on Conservation Measures for Important Areas and central Korea during the breeding of Cranes in East Asia. Wild Bird Society of season. The Changbaishan Mountains, Japan, Tokyo. (In Korean and Japanese.) the major breeding area in China Delacour, J. & Jabouille, P. 1931. Les Oiseaux (Zhao Zhengjie et al. 1994a), straddle de l’Indochine française, 1-4. Exposition the Korea/China border. Hyangsan Coloniale Internationale, Paris. Delacour, J., Jabouille, P. & Lowe, W.P. 1928. itself lies only c.250 km south of the On the birds collected during the third Changbaishan, and while the rivers in expedition to French Indo-China. Ibis (12)4: the immediate vicinity are too heavily 23-51; 285-317. disturbed for mergansers to be able to Fiebig, J. 1993–1995. Dreijährige ornithologische breed, the remoter rivers and streams Studien in Nordkorea. Mitteilungen aus dem Zoologischen Museum in Berlin 69, may still be suitable. Supplement: Annalen für Ornithologie 17: 93- 146; 71, Supplement: Annalen für Ornithologie Acknowledgements 19: 43-99. He Fen-Qi, Melville, D., Gui Xiao-Jie, Hong These observations were made during Yuan-Hua & Liu Zhi-Yong 2002. Status of the Scaly-sided Merganser wintering in the UNDP–GEF Project DRK/00/G35/ Mainland China in the 1990s. Waterbirds 25: A/1G/31 ‘Conservation of biodiversity at 462-464. in the DPR Korea’, and Hughes, B. & Hunter, J. (eds.) 1994. The Scaly- we thank the Government of DPR Korea, sided Merganser Mergus squamatus in Russia UNDP and the Wildlife Conservation and China, IWRB Threatened Waterfowl Specialist Group Special Publication No. 1. Society for financial and operational WWT, Slimbridge, UK. support. Other project staff generously Jia Shaobo, Jia Lu & Chen Jianxiu 2003. tolerated frequent and sudden vehicle Waterbirds and their ecological distribution stops during autumn 2003 and in 2004 in Liaocheng, Shandong Province. Chinese to check mergansers. Stuart Butchart, Journal of Zoology 38 (5): 91-94. (In Chinese.) Kolomiitsev, N.P. 1995. New data on moult in the Baz Hughes, Nial Moores, Colin Poole Scaly-sided Merganser Mergus squamatus. and Michael Rank specifically provided Russian Journal of Ornithology 4(1/2): 19-23. information about mergansers. (In Russian.) Li Wenfa, Zhao Hesheng, Wang Henggen & References Li Fangman 1998. Breeding population of Scaly-sided Mergansers found in Ning‘an, Heilongjiang. Chinese Journal of Zoology 33 Austin, O.L. 1948. The birds of Korea. Bulletin of (5): 37-38. (In Chinese.) the Museum of Comparative Zoology, Harvard Mikhailov, K.E. & Shibnev, Y.B. 1998. The University 101: 1-301. threatened and near-threatened birds of BirdLife International 2001. Threatened Birds of northern Ussuriland, south-east Russia, Asia: the BirdLife International Red Data Book. and the role of the Bikin river basin in their BirdLife International, Cambridge, UK. conservation. Bird Conservation International Bocharnikov, V.N. & Shibnev, Y.B. 1994. The 8: 141-171. Scaly-sided Mergansers in central Korea 141

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