Autumn is the season of two-way traffic

By late August the hedgerows are heavy with elderberries and the first apples are dropping, and the urgent business of spring — cuckoos calling, swallows prospecting the eaves — has already faded. What follows is arguably the richest birdwatching season of the British year, because in autumn the traffic runs in both directions at once. Our summer visitors are streaming south towards Africa, while birds from Scandinavia, Iceland and the high Arctic are arriving to spend the winter here, where the sea stays comparatively mild and the berry crop is far more dependable than snow.

The result is a fortnight or two in late September and October when almost anything can turn up, and when a quiet coastal field can hold half a dozen species that were not there yesterday.

Watching the summer visitors leave

Swifts go first, and they go quietly. Most have left Britain by mid-August, sometimes only days after the young fledge. Swallows and house martins linger longer, and on still September mornings you can find them lined up along telephone wires or skimming low over reedbeds, feeding hard before the crossing.

Look out too for the smaller departures. Wheatears and whinchats drop into coastal stubble and fence lines, spotted flycatchers appear in unlikely places — an allotment apple tree, a car park shrubbery — and yellow wagtails gather on damp pasture. These are not stragglers so much as birds already on the move, topping up fuel before the next leg south.

Arrivals from the north and east

The first redwings usually reach the east coast in late September. They are small, dark thrushes with a creamy stripe above the eye, and most of them pass overhead at night, announcing themselves with a thin, high tseep that carries beautifully through a quiet evening. Fieldfares follow through October — bigger, grey-headed, chuckling and chacking as they strip rowan and hawthorn.

Mixed in with them come bramblings, siskins, redpolls and the occasional rough-legged buzzard or great grey shrike. On the coast, pink-footed geese arrive in their thousands from Iceland, yapping flocks that pour into the Lancashire mosses, the Solway Firth and the north Norfolk coast. Whooper swans, fresh in from Iceland, follow in late October and November; their bugling calls over a flooded meadow on a frosty morning is one of the great sounds of the British autumn.

What weather actually helps

Migration is a weather game, and you can tilt the odds in your favour. Clear skies with a light tailwind from the north or north-east are the classic arrival conditions, especially in the days after a cold front pushes down the North Sea. Birds that set out over water on a fair night can be caught out when the wind swings, rain sets in or sea fog rolls across, and forced to land in the first suitable cover they meet.

• Northerly or north-easterly airstream: expect arrivals on east coast headlands, often in large numbers.
• Clear, calm nights: excellent for watching visible migration — listen for calls overhead after dark.
• Rain, drizzle or fog in the morning: "falls" of grounded migrants, sometimes in odd places well inland.
• Warm southerlies: usually quieter, with birds holding back on the continent.
• Timing: the first two or three hours after dawn are nearly always best.

Where to look — coast, wetland and garden

Classic headlands such as Spurn, Flamborough Head, Portland Bill and the northern isles do the heavy lifting, but you do not need a famous name. Any east-facing stretch with scrub, weedy fields and a bit of shelter will gather tired migrants after a fall.

Estuaries and wetlands come into their own later in the season. The Wash, Morecambe Bay, the Humber and the Solway Firth fill with geese, ducks and waders, while inland reservoirs and gravel pits pull in divers, grebes and scaup. Flooded meadows are worth a look after heavy rain.

And your own garden counts. Plant or leave a berry-bearing shrub — rowan, cotoneaster, holly, ivy — and redwings and fieldfares may strip it in an afternoon. Leave windfall apples on the grass, put out sunflower hearts and nyjer, and keep a shallow dish of fresh water topped up. A single holly bush can hold blackcaps and thrushes for weeks.

Recording your sightings responsibly

Your notes are genuinely valuable, but they are worth more when they are accurate. Record the date, the exact place, the species and a realistic count, and send them to your county bird recorder or a national recording scheme. Note visible migration too: a steady trickle of meadow pipits heading south-west tells a story that a single list cannot.

Arriving birds are exhausted and hungry, so give them space. Keep well back from roosts and hedgerow feeding flocks, keep dogs under control and on leads near fields, and never use playback to bring a migrant closer. Grounded birds need to feed, not to be chased for a photograph. Report any ringed bird you find — a ring number, date and place is a small gift to science — and if you find an exhausted bird, leave it be in cover rather than picking it up. Watch, count, note, and step away.