Smew Mergellus albellus Scientific name definitions

35–44 cm; male 540–935 g, female 510–650 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 55–69 cm. Smaller than any species of Mergus. Unmistakable, especially mainly white male ; note small bill, steep forehead, slight crest and very straight neck in flight (all of which features more reminiscent of Bucephala spp.), which is fast and agile, often in oblique lines or V formation when in flocks. Male in breeding plumage has mainly white head, neck, upper body and underparts , relieved only by black facial mask , some loose black feathers on nape and two narrow black lines from mantle down breast-sides and forming inverted V; rump and tail grey-black, primaries black and secondaries mainly so, except white trailing edge, inner tertials black, outer ones white, lesser wing-coverts black, median coverts white and greater coverts black with white tips; bill short and mainly grey, legs and feet greyish, and eyes reddish brown, becoming pale greyish white in older males; eclipse plumage is similar to adult female, but has black upperparts and white patch on median coverts. Female has crown , nape and hindneck rufous-brown, contrasting with white face and throat, while upperparts and tail dull grey, breast and flanks mottled dusky, becoming greyish white posteriorly, and has wings less patterned with white than male. Juvenile resembles female, but central wing-coverts have brownish tips and lores are dark brown (not black); iris dull grey-brown (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 ).

• Common Goldeneye x Smew (hybrid) Bucephala clangula x Mergellus albellus
• Smew x Hooded Merganser (hybrid) Mergellus albellus x Lophodytes cucullatus

Breeds from Scandinavia E in band between about 55° N and Arctic Circle to E Siberia (Kamchatka). Winters in North and Baltic Seas and from C Europe E to Black and Caspian Seas, E China, Korea and Japan.

Freshwater lakes, pools, slow-flowing rivers and muskegs in taiga zone during breeding season, with preference for lowland oxbow lakes amid forest (including drowned trees), especially within medium-sized valleys, and ogliotrophic lakes and rivers with nearby forest in montane or submontane regions (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 winter , on larger lakes, ice-free rivers (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 ), brackish coastal lagoons, estuaries; uncommonly on open sea and rarely in water more than c. 6 m deep (4 Snow, D. W., and C. M. Perrins, Editors (1998). The Birds of the Western Palearctic. Concise Edition. Volume 1. Non-passerines. Oxford University Press, Oxford, UK. Close ). On passage will even use small waterbodies and narrow streams (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 ).

Migratory; winters W & C Europe, E Mediterranean basin, Black Sea, S Russia, Middle East (mainly in Turkey), E China, Korea and Japan (exceptionally Taiwan) (5 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 W Palearctic is considered only accidental visitor to Iceland  , Faeroes, Spain, Balearic Is, Malta, Cyprus, Israel, Libya, Tunisia and Algeria (4 Snow, D. W., and C. M. Perrins, Editors (1998). The Birds of the Western Palearctic. Concise Edition. Volume 1. Non-passerines. Oxford University Press, Oxford, UK. Close ). Departure from breeding grounds commences Sept and is completed by early Oct, with main passage through Swedish hinterland and Baltic states in mid Oct to Nov and most arrivals in North Sea wintering grounds not until Dec or even Jan, following colder weather further E, while spring migration becomes obvious in Mar, although stragglers remain in wintering areas until Apr or even May, and immatures can remain at lower latitudes throughout first summer (4 Snow, D. W., and C. M. Perrins, Editors (1998). The Birds of the Western Palearctic. Concise Edition. Volume 1. Non-passerines. Oxford University Press, Oxford, UK. Close ). Some spatial differentation between sexes on wintering grounds, at least in Europe, where males concentrate in S Baltic, with females and immatures dominating flocks further S & W, e.g. in British Isles (4 Snow, D. W., and C. M. Perrins, Editors (1998). The Birds of the Western Palearctic. Concise Edition. Volume 1. Non-passerines. Oxford University Press, Oxford, UK. Close ). Three main wintering areas identified in W Eurasia, firstly in NW & C Europe, where concentrated in S Baltic and Netherlands, with smaller numbers reaching Britain (especially SE England), Ireland, Belgium and C Europe, particularly if weather inclement; in Black Sea/E Mediterranean region, where concentrated around Sea of Azov, with smaller numbers in W Black Sea, Hungary, N Greece and Turkey (4 Snow, D. W., and C. M. Perrins, Editors (1998). The Birds of the Western Palearctic. Concise Edition. Volume 1. Non-passerines. Oxford University Press, Oxford, UK. Close ); and finally in SW Asia, especially in N Caspian Sea and Uzbekistan, but large numbers may reach Iran in some winters (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 ). Has been suggested that most of those wintering in NW Europe are from breeding grounds in N Russia E to Pechora, with those wintering between the Black and Caspian Seas coming from further E (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 ). Vagrant to North America, where recorded in Alaska and S to California (mostly in winter to spring, but exceptionally in summer in Aleutians), as well as even more rarely across N states of USA and S provinces of Canada, E to New York and Ontario, respectively, again mainly in winter and spring (6 Howell, S. N. G., I. Lewington, and W. Russell (2014). Rare Birds of North America. Princeton University Press, Princeton, NJ, USA. Close ).

Aquatic invertebrates, mainly insects and their larvae, amphibians and some plant material (seeds, leaves and roots) (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 ); also fish |Male eating a fish , mainly in winter and early spring, both in fresh and salt water. Occasionally takes bread from humans (7 Zonfrillo, B. (2009). Goosanders taking bread. British Birds 102(9):509–510. Close ). Freshwater fish taken by adults including salmon, trout, gudgeon (Gobio gobio), roach (Rutilus rutilus), bleak (Alburnus alburnus), loach (Cobitidae), sticklebacks (Gasterosteidae), northern pike (Esox lucius), minnow (Phoxinus phoxinus), burbot (Lota lota), eel (Anguilla anguilla), perch (Perca fluviatilis) and common carp (Cyprinus carpio), while marine fish recorded in diet include plaice (Pleuronectes platessa), sand-eels (Ammodytidae), sandsmelts (Antherinidae), smelt (Osmerus esperlanus), blenny (Zoarces viviparous), Atlantic herring (Clupea harengus) and common bream (Abramis brama), all of which are usually 30–60 mm long, but occasionally reach 100–110 mm (carp and perch) or even 290 mm (eels) (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 ). Insects (both adults and larvae) are dominated by waterbeetles (Coleoptera), dragonflies (Odonata) and caddisflies (Trichoptera), but also takes crustaceans, molluscs, marine polychaetes and frogs (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 ). Diet in Sea of Azov (in Dec) comprised mainly of fish (69·4%), especially black-striped pipefish (Syngnathus abaster), Azov percarina (Percarina maeotica) and monkey goby (Neogobius fluviatilis), as well as invertebrates—crustaceans such as Dikerogammarus sp. and crabs Rhithropanopeus harrisi (5·6%), annelids (5·6%) and the mollusc Dreissena polymorpha (2.8%)—plus rhizomes of aquatic and coastal plants of the families Apiaceae, Cyperaceae and Poaceae (16.7%) (8 Savitskii, R.M. and Matishov, G.G. (2011). Winter ecology of the Smew (Mergus albellus) in the Sea of Azov. Russian J. Ecol.. 42(3): 260–262. Close ). Feeds mostly by diving from surface, scanning for food first with head immersed  , usually to depths of 1–4 m and for periods of < 30 seconds (exceptionally up to 45 seconds) (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 winter forms large dense flocks, sometimes thousands strong (even > 10,000), with strong cohesion, the birds diving mainly in unison, or occasionally birds at front of flock dive continuously, while those at back make short flights to catch up (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 ). Also consorts with other waterfowl, for example Mergus merganser, Aythya marila, A. ferina, A. fuligula, Bucephala clangula and Great Crested Grebes (Podiceps cristatus) in Sea of Azov (8 Savitskii, R.M. and Matishov, G.G. (2011). Winter ecology of the Smew (Mergus albellus) in the Sea of Azov. Russian J. Ecol.. 42(3): 260–262. Close ).

Vocalizes only infrequently, except during courtship  or in alarm; in display, male  gives soft but variable, mechanical-sounding rattle, “kur-rik” or “krr-eck”, initially rather high-pitched but slowing and sounding hesitant towards end, and likened to sound of fingernail being dragged only teeth of comb, whereas female (when inciting male to copulate) utters harsh, rattling “krrrr krrrr”, which can become louder and be accompanied by energetic movements; contact calls of ducklings comprise 2–4 notes, while their distress calls are slow and swooping, starting low and rapidly gaining pitch (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 ).

Starts Apr/May in S of range, or mid May to mid Jun in N (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 ). Seasonally monogamous, with pair-bonds forming mainly in late winter (late Dec onwards) (4 Snow, D. W., and C. M. Perrins, Editors (1998). The Birds of the Western Palearctic. Concise Edition. Volume 1. Non-passerines. Oxford University Press, Oxford, UK. Close ) or on migration, with males abandoning females during incubation period, prior to which male defends female (but not territory) (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 single pairs or loose groups; nest lined with some feathers and down (but usually no other material), in tree hollows (c. 10+ m above ground) (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 ), often those of Black Woodpeckers (Dryocopus martius) or in artificial nestboxes  . Usually 7–9 cream to pale buff eggs (5–11, but up to 14 recorded, presumably due to egg dumping) (4 Snow, D. W., and C. M. Perrins, Editors (1998). The Birds of the Western Palearctic. Concise Edition. Volume 1. Non-passerines. Oxford University Press, Oxford, UK. Close ), size 48–58 mm × 34–40 mm, mass (in captivity) 34·5–46 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 ); incubation 26–28 days by female alone, commencing when clutch complete and hatching synchronously (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 ); chicks have sooty black down above, white below and on dorsal spots, weigh c. 23 g on hatching (in captivity) (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 ); fledging c. 10 weeks, tended by female alone (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 Sweden, this species (and other diving ducks) appear to be negatively affected by breeding Black-throated Divers (Gavia arctica), apparently due to aggression by the divers (9 Bildström, L. (2006). Storlommens aggression mot dykänder vid häckplatser kring Skellefteälven, södra Lappland [Aggression by Black-throated Diver Gavia arctica on diving ducks at their breeding lakes around river Skellefteälven, southern Lapland]. Ornis Svecica. 16: 232–235. Close ). Sexual maturity probably at c. 2 years. No information on mean annual adult survival or longevity.

Not globally threatened (Least Concern). However, is considered Vulnerable in European context, where breeding populations are generally small, e.g. just 10–20 pairs in Norway (1970–1990, first bred 1925), 75–150 pairs in Sweden (late 1980s), 1000–2000 pairs in Finland (late 1980s) and 7000–15,000 pairs in European Russia (4 Snow, D. W., and C. M. Perrins, Editors (1998). The Birds of the Western Palearctic. Concise Edition. Volume 1. Non-passerines. Oxford University Press, Oxford, UK. Close ). Not uncommon, but local, winter visitor to Japan, where has bred, and also irregular breeding efforts elsewhere S of main range, e.g. in the Netherlands (since 2010) (10 Ławicki, Ł., and A. B. van den Berg (2016) WP reports. Dutch Birding 38: 322–336. Close ), Denmark (1993), Germany (in 2016) (10 Ławicki, Ł., and A. B. van den Berg (2016) WP reports. Dutch Birding 38: 322–336. Close ), Estonia (1–2 records), Czech Republic (1984) and Romania (no recent records) (4 Snow, D. W., and C. M. Perrins, Editors (1998). The Birds of the Western Palearctic. Concise Edition. Volume 1. Non-passerines. Oxford University Press, Oxford, UK. Close ). No global estimates of population size available, but winter population in W Palearctic estimated at c. 80,000 birds in mid 1980s, with marked decline evident in those in Azerbaijan at this 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 ) and overall total of perhaps 125,000–135,000 in W Eurasia at this season, of which c. 30,000 in NW Europe, in mid 1990s, when most important sites were known to be Ijsselmeer (Netherlands) and Szczecin Lagoon (Poland), although both required more systematic and simultaneous assessment (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 ), and recent counts at the latter site have been massively reduced (11 Skov, H., S. Heinänen, R. Žydelis, J. Bellebaum, S. Bzoma, M. Dagys, J. Durinck, S. Garthe, G. Grishanov, M. Hario, J. J. Kieckbusch, J. Kube, A. Kuresoo, K. Larsson, L. Luigujoe, W. Meissner, H. W. Nehls, L. Nilsson, I. K. Petersen, M. M. Roos, S. Pihl, N. Sonntag, A. Stock, A. Stipniece, and A. Wahl (2011). Waterbird Populations and Pressures in the Baltic Sea. TemaNord 2011:550. Nordic Council of Ministers, Copenhagen, Denmark. Close ). Indeed, the current Baltic winter population is estimated at 12,600 birds, or a decrease of 25·9% since 1988–1993, with this region now supporting 31·5% of the NW European winter population, compared to 68% in 1988–1993, and some spatial redistribution of the most important areas for the species within the region also evident (11 Skov, H., S. Heinänen, R. Žydelis, J. Bellebaum, S. Bzoma, M. Dagys, J. Durinck, S. Garthe, G. Grishanov, M. Hario, J. J. Kieckbusch, J. Kube, A. Kuresoo, K. Larsson, L. Luigujoe, W. Meissner, H. W. Nehls, L. Nilsson, I. K. Petersen, M. M. Roos, S. Pihl, N. Sonntag, A. Stock, A. Stipniece, and A. Wahl (2011). Waterbird Populations and Pressures in the Baltic Sea. TemaNord 2011:550. Nordic Council of Ministers, Copenhagen, Denmark. Close ). Much larger numbers presumed winter further E, in several parts of Asia and particularly W Siberia (where perhaps 72,000 birds in post-breeding season), with winter estimates of c. 35,000 in Black Sea/E Mediterranean region and 25,000–100,000 in E Asia (including 20,000 in China, 1000 in South Korea and 1900 in Japan) (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 ). Partial winter censuses in 1991, yielded 1646 in Turkmenistan. No indication of recent significant change in overall numbers (species declined during second half of 19th and early 20th centuries in Europe due to habitat loss and degradation, and predation by introduced American mink Mustela vison) (12 Vinogradov, V.G. (1994). Population trends of Smew Mergus albellus on East European plain in the 19–297 centuries. Journal of Ornithology. 13(2): 212-213. Close ); however, local decreases are evident in S European Russia and W & C Siberia (in 1972–1989), where formerly bred almost to Kazakh border (12 Vinogradov, V.G. (1994). Population trends of Smew Mergus albellus on East European plain in the 19–297 centuries. Journal of Ornithology. 13(2): 212-213. Close ), partially offset by increases in Belarus (where first bred in 1988 and 40–50 pairs by 1990) (4 Snow, D. W., and C. M. Perrins, Editors (1998). The Birds of the Western Palearctic. Concise Edition. Volume 1. Non-passerines. Oxford University Press, Oxford, UK. Close ), around St Petersburg (Russia) (12 Vinogradov, V.G. (1994). Population trends of Smew Mergus albellus on East European plain in the 19–297 centuries. Journal of Ornithology. 13(2): 212-213. Close ) and in Finland (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 ), and species reputed to be much affected locally by availability of nest sites in suitable habitat. On passage and in winter, subject to certain amount of hunting pressure and exposed to oil pollution where it occurs in numbers in coastal waters.