Why Estuaries Are the Place to Be

An estuary at high tide is one of the great spectacles of British wildlife watching, and it happens twice a day, often within sight of a car park. As the water pushes up the channel and covers the mudflats, thousands of wading birds are forced off their feeding grounds and onto whatever dry ground remains. That might be a shingle spit, a saltmarsh edge, a rocky shoreline or a field behind the sea wall. The result is a dense, noisy, restless gathering of birds packed together at close range — curlews, oystercatchers, dunlin, grey plover, knot, bar-tailed godwits and more.

These roosts are not just a convenient way to see a lot of birds quickly. They are essential to the birds' survival. A wader that has spent hours feeding on the mud needs to rest and digest, and it needs to do so without burning energy on flight or on constant alertness. Understanding that is the key to watching them well, and to watching them without causing harm.

Getting the Optics Right

Distance is your friend here. On a big estuary like the Dee, the Humber, the Severn or the Solway, birds will typically be several hundred metres away, and a pair of 8x or 10x binoculars will tell you there are waders out there but not much else. A telescope — a spotting scope on a sturdy tripod — transforms the experience. At 20x to 30x magnification you can pick out the long, gently curved bill of a curlew against the shorter, straighter bill of a bar-tailed godwit, or watch an oystercatcher hammering open a mussel.

• Magnification: a 20-60x zoom eyepiece covers most situations, but stay at the lower end for a wider, brighter view.
• Tripod: don't skimp. A flimsy tripod wobbles in the wind, and estuary winds are rarely gentle.
• Angle: a straight scope suits standing at a sea wall; an angled scope is kinder on the neck and easier to share with a companion.
• Hide or screen: where a public hide exists, use it. Otherwise use a sea wall, a hedge or a parked car as a visual barrier.

If you only have binoculars, don't despair — pick a roost site you can approach from behind cover, or visit on a rising tide when birds are pushed towards your side of the estuary.

Reading the Tide and the Season

Timing is everything. The best roosts are those where the high tide is big enough to cover the feeding flats completely. On spring tides — the biggest tides, around new and full moon — birds are pushed higher and closer, and the spectacle is at its best. On neap tides the mud may never fully cover, and the birds simply spread out and feed.

Arrive at least an hour before high water. The birds will already be gathering, flying in from all directions in loose lines and V formations, and you get to watch the roost build. An hour after high tide, the mud starts to reappear and the birds begin to drift away again.

Winter is the season for numbers. From October through to March, our estuaries hold birds that have bred in Iceland, Scandinavia, Siberia and the Canadian Arctic. Some are passing through; many stay. Ringed plover and dunlin peak in midwinter, while curlews are present in good numbers throughout. In spring and autumn, look for passage birds heading north or south, plus the first returning godwits in their rusty summer plumage — a genuinely spectacular sight.

Know Your Birds

At distance, most waders look like small grey-brown blobs. A few key features sort them out.

• Curlew: the largest European wader, long down-curved bill, mottled brown, often standing apart from the flock. Listen for the haunting "cur-lee" call.
• Oystercatcher: impossible to mistake — black and white, bright orange-red bill and legs, loud piping calls.
• Bar-tailed godwit: long pink-based bill, slightly upturned, grey above. In spring, brick-red underneath.
• Black-tailed godwit: longer legs, straighter bill, and a bold white wing-bar in flight. Often feeds in shallow water rather than on exposed mud.
• Dunlin and knot: small, tightly packed, moving like a single organism when a peregrine passes over.
• Redshank: medium-sized with bright orange-red legs and a pale trailing edge to the wing.

Learn the calls as well as the looks. Oystercatchers, curlews and redshanks are vocal and will often alert you to a flock you haven't yet spotted.

Roost etiquette: Keep Your Distance

Waders are remarkably tolerant of a telescope on a tripod, and remarkably intolerant of a person walking along the tideline. The difference is all about perceived threat. A stationary observer behind a wall is furniture; a walker with a dog is a predator.

• Stay on public footpaths and marked access routes, even when the mud looks firm. It usually isn't, and it's often dangerous.
• Keep dogs on a lead near roosts, and ideally leave them at home for a dedicated birdwatching trip.
• Never walk between the birds and the water. That cuts off their escape route and causes a mass flush.
• Don't approach to get a better photograph. If the flock lifts, you are too close — back off and let them settle.
• Watch for a "flush" — birds taking off en masse, calling in alarm. It means someone or something has disturbed them. Move away quietly.

A single disturbance might not seem much. But a roost that is flushed repeatedly through a cold winter afternoon burns energy the birds cannot afford to lose, and repeated disturbance can push them off a site altogether.

Some Estuaries Worth Visiting

The British coastline is rich in estuaries, and many have hides, reserves or sea walls that give excellent views without intruding. The Dee estuary from the Wirral side offers big, accessible roosts. The Humber has hides at several points along its banks. The Severn, the Solway, the Exe, the Teifi, the Ythan and Strangford Lough all hold internationally important numbers of waders and waders-watchers alike.

Wherever you go, check the local tide tables, aim for a spring high tide, take a scope if you can, and settle in behind whatever cover the site provides. The birds will do the rest — and if you keep your distance, they'll keep coming back.