Migration never really stops in a British wetland. Even in the quiet weeks of midsummer a Green Sandpiper drops onto a muddy corner, and by late September the same pool is crowded with Teal that arrived overnight. Knowing when birds move, and why, turns a pleasant walk into a morning you remember.

What follows is a seasonal guide to the movements you can expect in UK wetlands, how weather shapes them, and how to put yourself in the right place at the right time.

Why wetlands carry so much traffic

The UK sits at the western edge of the East Atlantic Flyway, the route linking breeding grounds in the Arctic and northern Europe with wintering areas in western Europe and Africa. Wetlands are the refuelling stops along it: shallow water, exposed mud, wet grassland and reedbed supply invertebrate-rich food and safe roosting.

Not every wetland is equal. Estuaries with wide tidal mudflats hold thousands of waders. Gravel pits and reservoirs attract diving ducks, terns and gulls. Wet grassland suits geese and swans, while reedbeds shelter Bitterns and Marsh Harriers and provide roosts for Swallows. Pick your site with the species in mind rather than simply the nearest car park.

Spring: a fast, northbound rush

Spring passage runs from late February into early June, and it feels urgent. Birds are heading to breeding grounds that may be thousands of miles further north, so many stop for a day or two and move on.

March and early April

Avocets return to coastal lagoons and flooded grazing marsh, often the first clear sign that passage has begun. Sand Martins appear over open water, Chiffchaffs sing from willow scrub, and Ospreys pass through, occasionally lingering at reservoirs and gravel pits where fish are easy to catch. Wigeon and Teal numbers fall away as wildfowl head back east and north.

Late April to early June

This is the peak. Garganey, our only summer-visiting duck, slips into shallow pools and is easily overlooked. Willow Warblers, Sedge Warblers, Whitethroats, Swallows and House Martins arrive in waves, with Swifts following in early May. On the coast, waders pass through in breeding dress: Whimbrel, Bar-tailed Godwit, Knot and Dunlin. Calm evenings over a gravel pit can bring Black Terns and Little Gulls hawking insects above the water.

Autumn: the long, drawn-out return

Autumn migration is bigger, slower and far easier to watch. It begins in June with failed breeders and non-breeding birds, and it does not finish until late November.

Waders lead the way. By early July, Green Sandpipers, Common Sandpipers, Ruff and returning Black-tailed Godwits are feeding on muddy edges. Through August and September the juveniles follow: Little Stints, Curlew Sandpipers, Spotted Redshanks and Wood Sandpipers among them. Adults arrive first, often still in worn breeding plumage, which is worth remembering when you are puzzling over a pale, spotty wader on a distant scrape.

Wildfowl come later and stay. Teal and Wigeon build through September and October. Pink-footed Geese arrive from Iceland and Greenland, and the first Whooper Swans appear in October, with Bewick's Swans following from late October into November. By December the wetlands belong to winter.

Reading the weather

Weather decides what you see on any given day. In spring, warm southerly winds help birds travel north early, while persistent north-easterlies hold them back and push them onto the east coast, producing falls of migrants in coastal scrub and marsh. Mist, drizzle and low cloud force birds to land, which is why a grey morning often beats a bright one.

In autumn, north-westerly gales push seabirds and waders closer inshore, and easterlies in late autumn bring cold-weather wildfowl in from Scandinavia. Long spells of high pressure with light winds and clear skies are the opposite: birds travel high and pass over unseen. On still nights you can hear them, with Redwings, thrushes and waders calling as they cross overhead.

The best migration mornings are rarely the prettiest.

Species to look for, season by season

  • Early spring (March to early April): Avocet, Sand Martin, Chiffchaff, Osprey; departing Wigeon and Teal.
  • Late spring (late April to May): Garganey, Swift, Sedge Warbler, Whimbrel, Black Tern, Little Gull.
  • Early autumn (July to September): Green Sandpiper, Ruff, Black-tailed Godwit, Little Stint, Curlew Sandpiper, Osprey.
  • Late autumn and early winter (October to December): Pink-footed Goose, Whooper Swan, Bewick's Swan, Wigeon, Pintail, Golden Plover, Dunlin.

Where to watch in UK wetlands

Anywhere with water, mud and reed will turn up something, but the best sites share a few features: a range of water depths, some wet grassland, and ideally a tidal edge.

Estuaries and tidal mudflats

Sites such as the Wash, Morecambe Bay, the Dee estuary and Lindisfarne concentrate waders as the tide rises. Time your visit for the two hours before high water, when birds are pushed off the mud and onto roosts and nearby lagoons, often at close range.

Freshwater marsh, gravel pits and reservoirs

Long-established reserves such as Slimbridge, Welney, Martin Mere, Minsmere, Titchwell and Rutland Water offer hides over shallow lagoons, grazed marsh and reedbed, which suits ducks, swans, terns and harriers. Reedbed edges at dusk give you a fair chance of Bittern and Marsh Harrier. The Ouse Washes and the Norfolk Broads are worth the journey when floods and frost shuffle birds around.

Making the most of a visit

  1. Check the wind first. A shift to southerlies in spring, or north-westerlies in autumn, can transform a site overnight. Local birding websites and reserve sightings pages are useful for this.
  2. Time it with the tide if you are visiting an estuary, and aim to be in a hide before first light on a promising morning.
  3. Take a scope if you can. Most passage waders and wildfowl sit well out on open water or mud, where binoculars struggle.
  4. Work the edges. Muddy margins, shallow pools and the strip where reed meets open water hold far more than the middle of a lake.
  5. Keep notes. Recording dates, wind direction and what you saw builds a picture of your local wetland that no guide can give you.
  6. Give birds space. Stay in hides, keep to paths, keep dogs on leads and avoid flushing roosts or feeding flocks, especially in cold spells when every calorie counts.

Migration is a moving target, and that is the pleasure of it. The same pool can be empty on Saturday and full of Teal and waders by Tuesday. Learn the seasons, watch the forecast, and go often. Wetlands reward repetition more than any other habitat in Britain.

Photo: Stuart Robinson / Pexels