Bewick's Swan
The Tundra Swan is a small Holarctic swan. The 2 taxa within it are usually regarded as conspecific but are also sometimes split into 2 species: the Bewick's Swan of the Palaearctic and the Whistling Swan of the Nearctic.
The Bewick's Swan was named in 1830 by William Yarrell after the engraver Thomas Bewick who specialised in illustrations of birds and animals.
The Bewick's Swan measures 45 to 55 inches in length with a wing span of 18.5 to 21.5 inches. Males are slightly larger and heavier than females. It is similar in appearance to the Whooper Swan but is smaller, shorter-necked and has a more rounded head shape. It has a variable bill pattern but always shows more black than yellow and having a blunt forward edge of the yellow base patch. The Whooper Swan has a bill that has more yellow than black and the forward edge of the yellow patch is usually pointed. The bill pattern for every individual Bewick's Swan is unique and scientists often make detailed drawings of each bill and assign names to the swans to assist with studying these birds.
As their common name implies, the Tundra Swan breeds in the Arctic and sub-Arctic tundra where they inhabit shallow pools, lakes and rivers. Unlike the Mute Swan, but like the other Arctic swans, it is a migratory bird. The winter habitat is mainly grassland and marshland, often near the coast.
The breeding range of the Bewick’s Swan extends across the coastal lowlands of Siberia from the Kola Peninsula east to the Pacific. It starts to arrive in its breeding range around mid-May and leaves for its winter range around the end of September. The populations west of the Taimyr Peninsula migrate via the White Sea, Baltic Sea and the Elbe estuary to winter in Denmark, the Netherlands and the UK where it is common in winter on a few RSPB and WWT reserves. Some birds also winter elsewhere on the southern shores of the North Sea. The Bewick’s Swans that breed in eastern Russia migrate via Mongolia and north China to winter in the coastal regions of Korea, Japan and south China, south to Guangdong and occasionally as far as Taiwan. A few birds from the central Siberian range also winter in Iran at the south of the Caspian Sea.
Arrival in the winter range starts about mid-October although most birds spend weeks or even months at favourite resting locations and will only arrive in the winter range in November or even as late as January. Departure from the winter range starts in mid-February.
Bewick’s Swans mate in the late spring, usually after they have returned to the breeding range. As is usual for swans, they pair monogamously until one partner dies. Should one partner die long before the other, the surviving bird often will not mate again for several years or even for the rest of its life.
The nesting season starts at the end of May. The pair build the large mound-shaped nest from plant material at an elevated site near open water and they defend a large territory around it. The pen (female) lays and incubates a clutch of 2 to 7 (usually 3 to 5) eggs whilst the cob (male) keeps a steady lookout for potential predators heading towards his mate and offspring. The time from egg laying to hatching is 29 to 30 days. Since they nest in cold regions, Bewick’s Swan cygnets grow faster than those of swans breeding in warmer climates and they may fledge in 40 to 45 days. Cygnets stay with their parents for the first winter migration and the family is sometimes even joined by their offspring from previous breeding seasons while on the wintering grounds. Bewick’s Swans do not reach sexual maturity until 3 or 4 years of age.
In summer, the diet of the Bewick’s Swan consists mainly of aquatic vegetation which it finds by sticking its head underwater or upending while swimming. It will also eat some grass growing on dry land. At other times of the year, leftover grains and other crops such as potatoes, picked up in open fields after harvest, make up much of the diet.
Healthy adult Bewick’s Swans have few natural predators. The Arctic Fox may threaten breeding females and particular the eggs and hatchlings. Adults typically can stand their ground and displace foxes but occasionally the foxes are successful. Other potential nest predators include the Red Fox, the Brown Bear, the Golden Eagle, the Arctic Skua and the Glaucous Gull. The Brown Bear, the Golden Eagle and the Wolf may occasionally succeed at capturing and killing an adult. About 15% adults die each year from various causes and the average lifespan in the wild is about 10 years.
The status of the Bewick's Swan is not well known although its population is in decline in north west Europe for largely unexplained reasons. It is increasingly dependent on agricultural crops to supplement its winter diet as aquatic vegetation in its winter habitat declines due to habitat destruction and water pollution. However, the main cause of adult mortality is hunting and, whilst the Bewick's Swan can not be hunted legally, almost half the birds studied contain lead shot in their bodies, indicating that they were shot at by poachers. Lead poisoning by ingestion of lead shot is also a very significant cause of mortality. The Bewick's Swan is one of the birds to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.
Date: 9th January 2022
Location: WWT Slimbridge, Gloucestershire
The Bewick's Swan was named in 1830 by William Yarrell after the engraver Thomas Bewick who specialised in illustrations of birds and animals.
The Bewick's Swan measures 45 to 55 inches in length with a wing span of 18.5 to 21.5 inches. Males are slightly larger and heavier than females. It is similar in appearance to the Whooper Swan but is smaller, shorter-necked and has a more rounded head shape. It has a variable bill pattern but always shows more black than yellow and having a blunt forward edge of the yellow base patch. The Whooper Swan has a bill that has more yellow than black and the forward edge of the yellow patch is usually pointed. The bill pattern for every individual Bewick's Swan is unique and scientists often make detailed drawings of each bill and assign names to the swans to assist with studying these birds.
As their common name implies, the Tundra Swan breeds in the Arctic and sub-Arctic tundra where they inhabit shallow pools, lakes and rivers. Unlike the Mute Swan, but like the other Arctic swans, it is a migratory bird. The winter habitat is mainly grassland and marshland, often near the coast.
The breeding range of the Bewick’s Swan extends across the coastal lowlands of Siberia from the Kola Peninsula east to the Pacific. It starts to arrive in its breeding range around mid-May and leaves for its winter range around the end of September. The populations west of the Taimyr Peninsula migrate via the White Sea, Baltic Sea and the Elbe estuary to winter in Denmark, the Netherlands and the UK where it is common in winter on a few RSPB and WWT reserves. Some birds also winter elsewhere on the southern shores of the North Sea. The Bewick’s Swans that breed in eastern Russia migrate via Mongolia and north China to winter in the coastal regions of Korea, Japan and south China, south to Guangdong and occasionally as far as Taiwan. A few birds from the central Siberian range also winter in Iran at the south of the Caspian Sea.
Arrival in the winter range starts about mid-October although most birds spend weeks or even months at favourite resting locations and will only arrive in the winter range in November or even as late as January. Departure from the winter range starts in mid-February.
Bewick’s Swans mate in the late spring, usually after they have returned to the breeding range. As is usual for swans, they pair monogamously until one partner dies. Should one partner die long before the other, the surviving bird often will not mate again for several years or even for the rest of its life.
The nesting season starts at the end of May. The pair build the large mound-shaped nest from plant material at an elevated site near open water and they defend a large territory around it. The pen (female) lays and incubates a clutch of 2 to 7 (usually 3 to 5) eggs whilst the cob (male) keeps a steady lookout for potential predators heading towards his mate and offspring. The time from egg laying to hatching is 29 to 30 days. Since they nest in cold regions, Bewick’s Swan cygnets grow faster than those of swans breeding in warmer climates and they may fledge in 40 to 45 days. Cygnets stay with their parents for the first winter migration and the family is sometimes even joined by their offspring from previous breeding seasons while on the wintering grounds. Bewick’s Swans do not reach sexual maturity until 3 or 4 years of age.
In summer, the diet of the Bewick’s Swan consists mainly of aquatic vegetation which it finds by sticking its head underwater or upending while swimming. It will also eat some grass growing on dry land. At other times of the year, leftover grains and other crops such as potatoes, picked up in open fields after harvest, make up much of the diet.
Healthy adult Bewick’s Swans have few natural predators. The Arctic Fox may threaten breeding females and particular the eggs and hatchlings. Adults typically can stand their ground and displace foxes but occasionally the foxes are successful. Other potential nest predators include the Red Fox, the Brown Bear, the Golden Eagle, the Arctic Skua and the Glaucous Gull. The Brown Bear, the Golden Eagle and the Wolf may occasionally succeed at capturing and killing an adult. About 15% adults die each year from various causes and the average lifespan in the wild is about 10 years.
The status of the Bewick's Swan is not well known although its population is in decline in north west Europe for largely unexplained reasons. It is increasingly dependent on agricultural crops to supplement its winter diet as aquatic vegetation in its winter habitat declines due to habitat destruction and water pollution. However, the main cause of adult mortality is hunting and, whilst the Bewick's Swan can not be hunted legally, almost half the birds studied contain lead shot in their bodies, indicating that they were shot at by poachers. Lead poisoning by ingestion of lead shot is also a very significant cause of mortality. The Bewick's Swan is one of the birds to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.
Date: 9th January 2022
Location: WWT Slimbridge, Gloucestershire
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Also in: Whooper and Bewick's Swans
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