Why estuaries pull in the waders

An estuary at low water is one of the great spectacles of British wildlife, and it costs nothing but a pair of boots and a bit of patience. As the tide drops, kilometres of mudflat and sandbank emerge, and with them the invertebrates that wading birds depend on: ragworm, lugworm, cockles, small snails and crustaceans. For a few hours each day the table is laid.

That is why our larger estuaries hold birds in extraordinary numbers. Knot and dunlin gather in thousands, often tens of thousands, on the bigger systems. Curlew probe the mud with those long, curved bills, oystercatchers hammer at mussel beds, redshank and spotted redshank pick delicately at the shallows, and bar-tailed godwits feed with a steady, sewing-machine rhythm. Grey plover, ringed plover, turnstone and shelduck all turn up in the mix. Their presence is the reason so many estuaries carry special protection, and it is also the reason a little care from visitors matters so much.

Read the tide before you read the birds

The single most useful piece of planning is the tide table. Waders live by the tide, and so should you. On most estuaries the best window is the two to three hours either side of low water, when the mud is newly exposed and the birds are feeding hard. Arrive as the water is still draining away and you can often watch the flock follow the retreating edge out across the flats, a slow, shuffling movement of hundreds of birds.

As the tide turns, everything reverses. The birds are pushed back up the shore, and on a big tide they gather in roosts on saltmarsh, shingle spits or the last remaining banks. High-tide roosts can be superb, but they are usually further away and tightly packed, so a telescope helps enormously.

Spring tides expose much more mud than neap tides, and the difference in bird numbers between the two can be startling. Local tide tables are published free by harbour authorities and in local papers, and they are worth checking the night before.

What to take with you

• Binoculars. Something around 8x42 is the sensible all-round choice — bright enough for grey winter light, wide enough to follow a moving flock.
• A telescope. Not essential, but if you get serious about waders it will change what you can identify. A modest scope on a sturdy tripod beats an expensive one that shakes.
• Wellies and waterproof trousers. Estuary edges are wet, muddy and often windy, even on a bright day.
• Warm layers, hat and gloves. Mudflats are cold places, and you will be standing still for long stretches.
• A field guide and a notebook. Jot down counts, tide state and weather; over a season those notes become genuinely useful.

Keep your distance, keep the flock settled

This is the part that matters most. A flock that takes flight has just spent energy it cannot easily replace, and on a cold February afternoon repeated disturbance can genuinely affect a bird's chances. Walk slowly, keep to the sea wall, footpath or hide, and use your optics rather than your legs to get closer. Keep dogs on a short lead near the shore, and give roosting flocks a wide berth — a hundred metres is a reasonable rule of thumb, more if the birds are already restless.

Watch for the warning signs: heads up, nervous shuffling, alarm calls, a few birds lifting off. If you see them, stop and back away. Never walk out onto mudflats; they are dangerous as well as disruptive, and a rising tide can cut off a channel behind you in minutes.

Between roughly April and July, ringed plover, oystercatcher and lapwing nest on shingle, upper shore and saltmarsh. These nests are little more than a scrape, easily crushed and easily disturbed. Respect seasonal signage and any temporary path closures on protected sites — they exist for good reason, and the birds repay the courtesy in autumn and winter.

Seasons and what you might see

Winter, from November to February, is the peak. Numbers are at their highest, the birds are in duller plumage but easier to watch in concentrated flocks, and a hard frost often pushes them closer to the shore.

Spring brings passage birds heading north — whimbrel in April and May, curlew sandpiper and little stint on the move — alongside displaying redshank and drumming snipe on the saltmarsh. Summer is quieter on the flats but good for breeding shelduck and young oystercatchers, while autumn from July onwards delivers the first returning adults and then the juveniles, often the most approachable birds of the year.

A few habits of a good estuary watcher

Go early, or go on a rising tide when the birds come to you. Learn the calls before you learn the plumages — curlew, whimbrel and godwit are far easier on the ear than on the eye. Talk to local bird recorders and reserve wardens; estuary knowledge is generously shared. Record your counts, however rough, and leave the shore exactly as you found it. Do all that and the estuary will keep giving, tide after tide.