A winter estuary can throw four long-billed, long-legged waders at you in a single sweep of the binoculars, and at first glance they all look like the same bird. Curlew and whimbrel share the same shape and the same curve of bill. Black-tailed and bar-tailed godwit differ by a tail band you cannot see from the front. The trick is not to memorise everything at once. Judge the bill, check the legs, wait for a call, and watch how the bird feeds. Those four things will get you there.

Bill length and shape do most of the work

Proportions are the quickest clue, and you can usually judge them before the bird moves. Compare the bill with the head and body rather than trying to guess centimetres at range.

• Curlew. The longest bill of the group, in some females roughly a quarter of the bird's total length, and evenly decurved from base to tip. A feeding curlew often buries the whole bill and leaves just a head and shoulders above the mud. Males are noticeably shorter-billed, so a small curlew with a modest bill is still a curlew.
• Whimbrel. A shorter, neater bill with a distinct bend near the tip rather than a smooth arc. The head looks smaller and more finely marked, and the whole bird is darker and more compact.
• Bar-tailed godwit. A long bill that is essentially straight, with a subtle upward tilt towards the tip. The bird looks compact and rather front-heavy, often with a slightly hump-backed feeding posture.
• Black-tailed godwit. A long straight bill, fine and slightly tapered, with no upward kink. Paired with long legs, it gives a tall, elegant impression that bar-tailed godwit never quite manages.

Legs, tails and flight marks

Standing birds

Curlew and whimbrel both have blue-grey legs, with the whimbrel's usually the darker, bluer grey, but do not rely on that on its own. Both godwits have dark, greenish-black legs, so length is the giveaway. Black-tailed godwit stands noticeably leggier than bar-tailed, and those legs trail well beyond the tail in flight.

In flight

Black-tailed godwit is the showy one: a bold white wing bar, a white rump and a solid black tail band. Bar-tailed godwit shows a thinner, less obvious wing bar and a white rump that extends in a narrow wedge up the back, with a finely barred tail rather than a solid black band. Summer plumage makes it easier still. Bar-tailed turns deep brick red across the underparts, while black-tailed is bright orange-rufous on the head, neck and breast with a paler belly.

Listen: the calls settle it

Waders call far more than beginners expect. Learn four sounds and you will identify birds you never manage to see well.

• Curlew: a haunting cour-li, with the second note higher and held. The display song is a long bubbling trill that carries across moorland.
• Whimbrel: a fast, rippling whistle of about seven notes, titter-titter-titter. It is why the bird is sometimes called the seven whistler, and it usually gives the flock away before you find it.
• Bar-tailed godwit: a nasal, slightly complaining kyoo-kyoo or kirrick, often from tight roosting flocks.
• Black-tailed godwit: a ringing, repeated wicka-wicka-wicka, given freely in flight and by feeding flocks.

Habitat and behaviour

Where a bird is and what it is doing is often the last piece of the puzzle.

• Curlew is the generalist. Estuaries and mudflats in winter, rough pasture, stubbles and wet fields inland, and upland moorland when breeding. It walks slowly and deliberately, probing deep with long pauses between steps.
• Whimbrel is mainly a passage bird here. Look for it on rocky shores, coastal grassland and mudflats in late April and May, and again from July to September. It picks food from the surface with quick, neat pecks rather than deep probing, and often feeds alone or in small parties. A few pairs breed in northern Scotland.
• Bar-tailed godwit prefers sand. It feeds on sandy estuaries and beaches, frequently standing in shallow water and sometimes wading belly-deep while probing wet sand. At high tide it packs into tight roosts on sandbars and islands.
• Black-tailed godwit prefers mud. Lagoons, muddy estuaries, wet meadows and inland scrapes suit it, and it often feeds in shallow water in loose, busy flocks, wading forward with a steady rhythm.

Use the calendar as a clue

Whimbrel is the one to expect on passage rather than in midwinter, so a "curlew" on a rocky shore in May deserves a second look. Curlew is present all year and is the default long-billed wader almost anywhere in Britain. Bar-tailed godwit is chiefly a winter visitor and passage migrant on the coast. Black-tailed godwit winters here too, but spring and autumn birds may be continental migrants heading further south, while the Icelandic population settles in for the winter. Many carry colour rings, and noting down the combination is a genuinely useful thing to do.

Five habits that make wader identification easier

1. Get the bill first. Note the length and the curve before the bird moves or tucks its head.
2. Check the legs next. Grey-blue or dark green-black, short or long.
3. Wait for a call. Give it a minute. Flight calls are the fastest route to certainty.
4. Watch the feeding action. Deep probing in mud, probing in water, or quick surface pecks.
5. Write down the date and place. Passage patterns only make sense once you keep a simple notebook of what you saw and when.

Start with the easy version of each bird. A summer-plumaged black-tailed godwit, a whimbrel calling overhead, a curlew on a moorland fence post: learn those first, and the grey-brown winter birds on a distant mudflat will fall into place sooner than you expect. If you remember only two rules, make them these. A long bill on grey legs means curlew or whimbrel, and a white wing bar with a black tail band means black-tailed godwit.

Photo: 3503898 / Pixabay