Identifying common seabirds on estuary walks

Why estuaries are a birdwatcher's paradise

An estuary at low water looks, at first glance, like a great deal of mud. Look again. Those grey-brown flats are a larder, packed with ragworms, cockles, mussels and shrimps, and they draw in some of the most distinctive birds in Britain. Harbours, inlets and river mouths are among the most important feeding grounds in Europe, especially in winter, when numbers swell with arrivals from Iceland and the high Arctic. The good news is that you need no specialist kit to tell the main characters apart — silhouette, call and behaviour will do most of the work.

Oystercatchers: the noisy ones

You will usually hear oystercatchers before you see them: a loud, piping kleep-kleep, repeated with real urgency and carrying far across water. In flight they are boldly black and white with a broad white wing bar; on the ground they look stocky and slightly hunched, with a long, straight orange-red bill and pink legs. That combination is unmistakable.

Watch what the bill does. Oystercatchers stab at mussel beds and cockle grounds, and you will also see them on rocky shores and harbour walls, chiselling limpets from stone. In hard weather, flocks move onto grass fields inland. Listen for that same piping call after dark — they are famously vocal at night.

Curlews: the quiet ghosts of the mudflats

The curlew is our largest wading bird and, seen well, the easiest to name: long legs, mottled brown-grey plumage, and a long bill curving smoothly downwards. Standing birds often look hunched and faintly melancholy, head tucked into the shoulders between bouts of feeding. In flight, look for the pale rump and steady, unhurried wingbeats, usually in loose lines rather than tight flocks.

The call gives it away — a single, drawn-out cur-lee, rising then falling, the sound of a British estuary. On late-winter and spring evenings, displaying birds bubble and ripple over the saltmarsh. Curlews probe deep into soft mud for worms and crabs, so they need the flats at low tide, and the UK holds a large share of the world population. Disturbance costs them dearly.

Little egrets: the elegant newcomers

Thirty years ago a little egret in Britain was an event. The first birds colonised in the late 1980s and early 1990s; now they are a familiar sight on southern and eastern estuaries, spreading steadily north and west. Brilliant white, slim and long-necked, with a black bill, black legs and — the detail that settles it — bright yellow feet. The old nickname is 'the bird with the golden slippers'.

Little egrets hunt actively, which separates them from grey herons. Where a heron stands statue-still, an egret shuffles its feet in the shallows to flush small fish and shrimps, then stabs sideways with a flick of the head. In flight it looks compact and rather hunched, legs trailing, feet often just visible.

Reading the tide, the call and the silhouette

Timing beats luck on an estuary. Mudflats are most productive in the two or three hours either side of low water, when the feeding grounds are exposed. As the tide pushes in, birds are forced closer to shore, which is good for views but harder for them: less room, more energy spent. High water is roosting time, when waders gather on undisturbed spits and saltmarsh edges to rest and preen.

Three habits will speed up your identification. First, learn silhouettes — chunky with an orange bill (oystercatcher), long-billed and hunched (curlew), slim and snowy with a dagger bill (little egret). Second, learn two calls: the oystercatcher's pipe and the curlew's rising fall. On a windy estuary you will identify more birds by ear than by eye. Third, watch behaviour before reaching for the book; feeding method, posture and flight style are often more reliable than colour in flat light.

Watching without disturbing

Estuaries are working landscapes and fragile ones. Disturbance costs birds energy they cannot spare, especially in cold weather.

• Stay on the path or the sea wall, and use the highest ground you can find so your silhouette does not break the skyline above feeding birds.
• Keep a generous distance — at least 100 metres from feeding flocks — and use binoculars or a scope rather than walking closer.
• Never walk out onto exposed mudflats. You will push birds off the richest feeding areas, and estuaries hide soft patches and fast incoming tides.
• Keep dogs on a lead around waders and roosts. One sprint across the flats can clear hundreds of birds.
• Give roosting flocks a wide berth at high tide; they are resting, not loafing, and repeated flushing can be serious in freezing conditions.
• Move slowly and quietly, wear muted colours, and avoid following the waterline as the tide rises.

Do that, and you will see more, not less. Settle on a bench with a flask, let the tide do the work, and the estuary will come to you.