As the tide turns, the sky fills with thousands of birds.
As summer fades, migrating waders from Scandinavia arrive on the mud flats at Snettisham.
Knots might not be the biggest of birds but some travel thousands of miles to reach our shores. Over the last few days, vast flocks have arrived.
Muddy estuaries, like The Wash, are their favoured winter feeding grounds. They probe the salt flats looking for worms and shellfish with their stocky beaks.
Lizzie Bruce, from the RSPB said around 30,000 knot had already arrived at Snettisham.
"But they've only just started migrating back," she said. "At its peak in october we get up to 120,000 knots." When the highest tides fill the estuary to its brim, they take wing in their thousands.
Sometimes, they take flight when a predator like a marsh harrier looms overhead.
Thousands of dunlins, oyster catchers and curlews join the knots each winter.
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