From the Northern passages

Each October, the whooper swans from Iceland make their Irish landfall somewhere around Malin Head at the tip of the Inishowen Peninsula. Some flocks swing east a bit and arrive at Lough Foyle, planing down towards the big stretch of mud and polders on the Derry side. And some swing west a bit, ending up in the throat of Lough Swilly, Co Donegal. You can sit in the car on the causeway to Inch Island and have dozens of birds within a few yards, bugling softly to each other or stretching their necks to greet the latest arrivals from the north.

A good many whoopers stay for the winter at these northern sea loughs - 1,000 or more at Foyle, perhaps 600 at Swilly - but thousands more move on after the first assembly. There's a busy route to Britain, and another down to Lough Neagh and its annex, Lough Beg. From here a lot of the whoopers split up into smaller groups and fly off to the shallower lakes and turloughs of the midlands and west.

Watching Thallabawn's contingent rippling in over the duach to the lake, I like to think of this great flow of musical swans - 12,000 of them - fanning out across the island as if they owned it. And of all the other tribes of migrant birds who don't give a feather for borders. Icelandic wigeon, Canadian Brents, Greenland white-fronted geese all meet up at Lough Foyle for a first feed. At Strangford Lough, spectacular numbers of Brent geese arrive in October to feed on the eel-grass at the shallow end: flocks of thousands shift about with the tide. When the Zostera is well-cropped, a lot of the geese will move on south, to Dublin Bay, and more will carry on to Wexford, to feed beside the white-fronted geese on the slobs. For great flocks of Arctic waders, too - knot, dunlin, godwit, redshank and the rest - the east coast bays and estuaries are vital refuges on the East Atlantic Flyway.

To have some feeling for this restless flow of birds in autumn is to gain an image of Ireland in which the coast goes all the way round. A curiosity about nature is essentially holistic, and not content with vacant spaces on the map. It's a pity that travel in the North, at least on the motorways, prompts so little interest in the hidden countryside. Speed is isolating in itself, and the margin of farmland can be a lifeless diorama, all the one green and reeking of cattle slurry. Topography does not help: who, catching sight of a signpost to "Oxford Island" in the approaches to Craigavon, could guess that the biggest lake in Ireland or Britain lies so close?

The 387 square kilometres of water in Lough Neagh, set in a depression in Ulster's basalts, is roughly and dully quadrangular. Few roads run beside it, and there are no hills around it to offer an encompassing view. "Wide, flat, lonely shores," wrote Praeger in The Way That I Went, "of which cattle and birds are the prevailing inhabitants". In that respect, not much has changed in 60 years.

Beyond the reedbeds, the lake's peaty waters are nutrient-rich and turbid, and its margins seethe with midge larvae. This, and the general lack of disturbance, is sufficiently welcoming to waterfowl to make the lake, with adjoining Lough Beg, one of the most important wetlands in Europe.

In any season the system holds more duck than anywhere else in Ireland. In winter, the surface-feeding ducks, such as wigeon, teal, mallard, pintail, and shoveler, have their largest concentrations at Lough Beg, where clearer water allows much richer vegetation. Lough Neagh has the big flocks of migrant diving ducks: 21,000 pochard from Russia and eastern Europe, 23,000 tufted duck from Britain, Iceland and Scandinavia, and good numbers of goldeneye.

Some of these, at least, together with swans and perhaps a few Canada geese, should swim within binocular range of the hides at the Lough Neagh Discovery Centre at Oxford Island (open Wednesday to Sunday during winter). Look out, too, for the story of the pollan, the lake's herring-like fish which, together with the salmon, trout and char, swam into Ireland's chilly rivers 13,000 years ago and never stirred out again. It's exactly the same fish as the Arctic cisco, of rivers from the White Sea to Alaska, and its survival of Lough Neagh's modern pollution is a tribute to the oxygenating reach of the winds.

For a more tangible waterside thrill, try being around when four million gallons of sea surge in (or out) of the rocky narrows at the mouth of Strangford Lough, now a marine nature reserve. Pick a fortnightly "spring" tide and go along at Portaferry two or three hours either side of high tide: it's an awesome, turbulent sight. Look also for Portaferry's aquarium, Exploris, its sea-life stocked from the lough's 2,000-odd species.

A sense of connection with a more rough-hewn state of nature is one that crops up strikingly in some northern landscapes - mostly, it must be said, at their outer edges, where geology shapes all sorts of surprises. The sculpture of fire and ice are everywhere, not just in the basalt fantasy of the Giant's Causeway, but the black-and-white (basalt and chalk) cliffs of Rathlin Island, the young and jumbled granite of the Mournes. Or even on John Hewitt's Antrim coast, Groined by deep glens and walled along the west/ by the bare hilltops and the tufted moors . . .

A huge cultural investment in Irish landscape and nature has grown out of the north. I think not only of Praeger's tradition, but of Estyn Evans's inspirational reading of geography and folkways; of the poems of Heaney and Longley; of Piper's orchid paintings; of the palaeoecology at Queen's. All these have reached out into Ireland from a fascinating, well-loved corner of the island. Autumn, with its wild light, is an excellent time to see it.