Estuary notes, March.
The Common Shelduck (Tadorna tadorna) is one of the most striking ducks in the Western Palearctic. Bottle-green head, white body, chestnut breast band, and (in males) a bright red knob on a red bill. Roughly the size of a small goose, with a unique upright stance. Found on tidal mudflats and estuaries from Britain east across Eurasia. Population in Britain alone is around 80,000 birds.
Identification
A Shelduck in good light is unmistakable. Look for:
- Bottle-green head and upper neck - iridescent in sunlight.
- Bright white body with chestnut breast band wrapping around.
- Black flight feathers at wing tips, visible in flight.
- Red-orange bill with prominent fleshy knob (males only, larger in breeding season).
- Pink legs and feet.
- Goose-like size - 58-67 cm long, wingspan 1.1-1.2 metres.
Both sexes look broadly alike, which is unusual for ducks. The male is slightly larger and has the larger bill knob.
Where to find them
- Tidal mudflats and estuaries - the primary habitat.
- Salt marshes and coastal lagoons.
- Inland on shallow lakes in some breeding ranges.
Strongholds: north coast of Norfolk, Solway Firth, Wash estuary, Severn estuary in Britain. Further afield: Wadden Sea (Germany/Netherlands/Denmark), French Atlantic coast, Black Sea coast.
Behaviour
Some distinctive behaviours:
- Breeds in rabbit burrows or tree holes - unusual for a duck. Many use abandoned rabbit warrens on coastal dunes.
- Adult-led crèches - mothers gather ducklings from multiple families and lead the combined brood. Sometimes 50+ ducklings under 2-3 adults.
- Moult migration - most British Shelducks fly to the Wadden Sea in late summer for the flightless moult, returning in autumn.
- Pair-bonded - pairs stay together year-round.
The crèche behaviour is the most unusual: a single pair may lay 8-12 eggs, but rear a flock of 50 with shared parental duties.
Diet
Shelducks are filter-feeders on mud:
- Small molluscs - especially the laver spire snail (Hydrobia ulvae).
- Marine worms and crustaceans.
- Algae and seeds as supplement.
You can identify Shelduck feeding tracks on mudflats: a winding furrow where the bill has been swept side to side at low tide.
How to tell from other ducks
- vs Mallard - Shelduck is goose-sized and stands more upright; mallards are smaller and lower.
- vs Egyptian Goose - Shelduck has the green head and red bill knob; Egyptian has a brown body and dark eye patch.
- vs Northern Shoveler - shoveler has a spatulate bill, no knob, smaller.
Sibley Field Guide Birds of Eastern North America
For comparison plates.
The Common Shelduck is a Eurasian species but vagrants do appear on the east coast of North America - and the Sibley East volume covers them along with all the regular American waterfowl. Excellent for sorting "is that a shelduck or a Northern Shoveler" questions.
- Includes vagrant species records
- All native ducks plus comparison illustrations
- Compact, well-indexed
Sibley · 2nd Ed.
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The bottom line
The Common Shelduck is the most distinctive duck on the European coast - bottle-green head, chestnut sash, the only duck regularly using rabbit burrows for nesting. Best seen at any major estuary on a falling tide.
For more on European waterfowl, see North American geese for comparison.
