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Smew

Mergellus albellus

Despite being only a rare winter visitor to the British Isles, the Smew is one of the countrys most unmistakable and easily identified duck species. Breeding across Central Asia and returning to Western Europe during winter months, smews begin to turn up on inland lakes as well as in coastal regions from November onwards.

Smew

Smew

Smew

Two males and one female Smew

Smew

Juvenile Smew

Smew

Smew in-flight

Quick Facts

Classification

Scientific name:

Mergellus albellus

Family:

Ducks, geese and swans

Conservation status:

Amber

Measurements

Length:

36cm to 44cm

Wingspan:

55cm to 69cm

Weight:

500g to 800g

Appearance & Identification

What do Smews look like?

Male and female smews are completely unalike in appearance, but both are equally striking and immediately recognizable.

Male smews are mainly white, but have a black eye mask, black patch on the rear of the head, a black back, and two narrow black lines from the upper back to the breast. Wings are black, but patterned with grey and black.

Females have a white lower face and throat, chestnut-red crown, nape and upper neck, and dusky grey wings and back. Its flanks and lower belly are mottled grey-white.

Both males and females have grey legs and feet, a short grey bill, and a vague crest on the back of their head.

Non-breeding males moult into an eclipse plumage that is fairly similar to the colouring of a female smew, but retain their black backs and white wing patches.

Juvenile smews are also similar in appearance to females, but are browner instead of grey-black.

Smew in natural habitat

Male Smew

Female smew

Female Smew

How big are Smews?

Compact diving ducks, smews are the smallest member of the typical mergansers, with males larger in size and weight than females.

  • Length: 36 cm to 44 cm (14.2 in to 17.3 in)
  • Wingspan: 55 cm to 69 cm (21.7 in to 27.2 in)
  • Weight: 500 g to 800 g (17.6 oz to 28.2 oz)
Smew standing on rocks

Smew standing on rocks

Calls & Sounds

What sound does a Smew make?

Not the most vocal of waterbirds, a smew’s call is usually heard only during courtship or alarm. Male smews make a mechanical-sounding ‘kurr-ik kurr-ik’ rattle, while the alarm call of female smews is a harsher ‘krrrrr’.

Smew swimming in natural habitat

Smew swimming in natural habitat

Diet

What do Smews eat?

Smews feed by diving underwater to search for prey, finding aquatic insects and fish, larvae, amphibians, and some plant matter.

Water beetles and dragonflies are the main insects eaten, although crustaceans and molluscs also feature, particularly in summer.

In winter, more fish, including salmon, trout, gudgeon, herring, eels, and carp, are caught, depending on location, with both freshwater and saltwater species eaten.

Despite their small size, smews are able to catch relatively large fish, with eels up to 29 cm not posing much of a problem! Their serrated bills have a sharp, hooked end, which allows them to firmly grip hold of their prey.

What do baby Smews eat?

Baby smews initially feed mainly on small aquatic invertebrates and their larvae, particularly dragonflies and caddisflies.

Female Smew with her baby

Female Smew with her baby

Habitat & Distribution

What is the habitat of a Smew?

During the breeding season, habitats preferred by smews include freshwater lakes, pools, slow-flowing rivers and lowland oxbow lakes.

Winter habitats include large lakes, coastal lagoons and estuaries, and ice-free slow-flowing rivers.

What is the range of a Smew?

The breeding range of smews extends from Scandinavia in the east, across Russia into eastern Siberia in the west, reaching as far north as the Arctic Circle.

The species’ winter range includes the North and Baltic seas to the east, and from central and eastern Europe to the Black and Caspian seas, as far east as Japan, the Korean peninsula and eastern China.

Where do Smews live?

The leading European countries with the highest breeding populations include Finland and Russia, while little is known about the species on breeding grounds outside of Europe.

Winter visitors to western Europe are concentrated around the Netherlands and Denmark.

close-up of a Smew

close-up of a Smew

How rare are Smews?

Only around 125 smews visit the UK each winter, with no breeding recorded in the British Isles, so they can certainly be considered a rare visitor.

Where can you see Smews in the UK?

Small numbers of smews arrive in the UK each winter from Russia and Scandinavia, and arrivals are mainly spotted in coastal regions from Lincolnshire to the Severn estuary. However, they are frequently spotted on inland lakes and ponds too, rather than being purely limited to coastal waters.

Smew getting ready for take-off

Smew getting ready for take-off

Lifespan & Predation

How long do Smews live?

Little information is available about the average expected lifespan of a smew. First-time breeding is thought to occur at 2 years of age.

What are the predators of Smews?

Natural predators of smews across their distribution range include American mink, long-legged buzzards, rough-legged buzzards, peregrine falcons, merlins and hen harriers. In some parts of Europe, smews are shot in substantial numbers by recreational hunters.

Are Smews protected?

Smews are protected by the Wildlife and Countryside Act, of 1981, which makes it an offence to knowingly kill, injure or take one into captivity.

Are Smews endangered?

Smews are categorised with Red status on the British Birds of Conservation Concern list, due to a 66 percent decline in numbers from 1993 to 2018.

It is considered a vulnerable species in parts of its European range, with population declines linked to habitat loss and degradation, and predation, particularly by American mink.

Female Smew resting on the rocks

Female Smew resting on the rocks

Nesting & Breeding

Where do Smews nest?

Smews are cavity nesters, and frequently use abandoned hollows excavated by black woodpeckers or artificial nest boxes.

A sparse lining of feathers is added to the bottom of the hollow, but no other nesting materials are used. Nests are generally located no more than 10 m (33 ft) above ground level.

When do Smews nest?

The breeding season for smews begins from April onwards, and can be delayed until June in the more northerly regions of their range. One brood is laid per season.

What do Smew eggs look like?

Smews’ eggs measure 53 mm by 38 mm (2.1 in by 1.5 in) and are cream to pale buff in colour. A typical clutch consists of between 7 and 9 eggs, which are incubated by the female alone for 26 to 28 days.

The male initially stands guard nearby, but as the incubation period progresses, leaves the breeding grounds and plays no active part in raising the ducklings once they hatch.

Do Smews mate for life?

A seasonally monogamous species, smew pairs form on wintering grounds or during migration and remain together until the female is partway through incubating her eggs.

Males depart for moulting grounds before the young hatch, and play no active role in raising their ducklings.

Pair of Smews performing mating ritual

Pair of Smews performing mating ritual

Behaviour

Are Smews aggressive?

It’s not thought that smews are an especially aggressive species, and do not show signs of territorial behaviour, even during the breeding season.

The male defends his mate during the early incubation period, but do not defend a particular territory

Two Smews resting on the rocks

Two Smews resting on the rocks

Migration

Do Smews migrate?

Smews are a fully migratory species, breeding in the extreme northern regions of Scandinavia, and Russia, and moving south once winter approaches.

Winter populations are found across central and western Europe, as well as in south-west Asia, particularly Iran and Uzbekistan.

Are Smews native to the UK?

Smews are winter visitors to the UK but do not breed anywhere in the British Isles. They arrive from November onwards, when conditions in their Scandinavian and Russian breeding grounds become too harsh to survive, and have all departed by early the following spring.

Male (left) and Female (right) Smews in-flight

Male (left) and Female (right) Smews in-flight

FAQs

Is a Smew a sea duck?

The Smew is a sea duck. It is a small diving duck belonging to the family Anatidae.

How do you pronounce Smew?

Smew is pronounced as it is written ‘S-mew’, to rhyme with ‘new’.

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