Over the past winter leading up to the first confirmed case of bird flu in the UK, 10 species of wildfowl have been monitored by experts as potential importers of the virus. They are listed below.
Some of the 10 species have populations resident in the UK all year round, but all have had significant numbers coming to the UK either as part of their annual long distance seasonal migration, or after being driven here by freezing weather in the east.
The seasonally migrating populations are now on the move again, heading north, to their Arctic breeding grounds.
BEWICK'S SWAN
Number in UK: 9,000 individuals in winter only (a third of the European population)
Breeds: Northern Eurasia and northern North America
Habitat: Lakes, ponds and rivers, plus estuaries when migrating
Diet: Plant material including tubers, shoots and leaves
MALLARD
Number in UK: 138,000 breeding pairs, plus 500,000 individuals in winter
Breeds: Eurasia, North America
Habitat: Anywhere with water
Diet: Seeds, acorns and berries, plants, insects and shellfish
PINTAIL
Number in UK: Tiny numbers of breeding pairs, 28,000 individuals in winter
Breeds: North and central Europe, Asia, North America
Habitat: Lakes, rivers, marsh and tundra
Diet: Plants and small animals, feeds on mud bottom at depths of 10-30cm (four-12 inches)
POCHARD
Number in UK: 80,000 individuals in winter only
Breeds: Europe, north and central Asia
Habitat: Lakes, slow rivers and estuaries
Diet: Range of plants and small insects, also small animals
SHOVELER
Number in UK: 1,000-1,500 breeding pairs, plus 18,000 individuals in winter
Breeds: North and central Europe, Asia, North America
Habitat: Shallow lakes, marshes, reed beds and wet meadows
Diet: Small insects, crustaceans, molluscs, seeds
TEAL
Number in UK: 2,600 breeding pairs, plus 197,000 individuals in winter
Breeds: North and central Eurasia
Habitat: Lakes, marshes, ponds and shallow streams
Diet: Range of plants and small insects, mostly seeds in winter
TUFTED DUCK
Number in UK: 7,000-8,000 breeding pairs, plus 60,000 individuals in winter
Breeds: North and central Europe, Asia, North America
Habitat: Shallow lakes, marshes, reed beds and wet meadows
Diet: Small insects, crustaceans, molluscs, seeds
WHITE-FRONTED GOOSE
Number in UK: 36,000 individuals in winter only
Breeds: Northern Russia, North America and western Greenland
Habitat: Tundra lakes, wet meadows and flooded fields and estuaries when migrating
Diet: Plant material including roots, tubers, shoots and leaves
WHOOPER SWAN
Number in UK: Over 10,000 individuals in winter only
Breeds: Northern Russia, northern North America and western Greenland
Habitat: Tundra lakes and wet meadows, plus flooded fields and estuaries when migrating
Diet: Plant material including roots, tubers, shoots and leaves
WIGEON
Number in UK: Tiny numbers of breeding pairs, over 500,000 individuals in winter
Breeds: North and central Europe, Asia
Habitat: Marsh, lakes, open moor, and estuaries when migrating
Diet: Mostly leaves, shoots, rootstock, also some seeds
Sources: British Trust for Ornithology; RSPB; Department for Environment, Food and Rural Affairs.