In a space smaller than many cities’ commuter belts, three completely different migration highways cross at once: over the mountains, through the marshes, and out at sea. That overlap is what makes this corner of Europe rare.
In the first article we saw why so many birds pass through the Basque Country. It funnels the huge numbers of soaring birds that come down the western side of Europe and do not want to cross open sea. That alone would make it notable.
But the funnel is only part of the story. What makes this small territory genuinely world-class is that it is not one migration route. It is three, stacked on top of each other in an area you could drive across in an hour. Over the ridges, the soaring birds. Down in the estuaries, the waders and the reedbed birds. Out beyond the beaches, the seabirds. Three completely different kinds of journey, using three completely different habitats, all crossing the same patch of map at the same time of year. Very few places on Earth put all of that so close together.
Highway one: over the mountains
The mountain passes carry the birds that travel by soaring, riding warm rising air and gliding forward without flapping. Because they cannot climb over open water, they pile up against the Pyrenees and cross at the lowest gaps.
The three main passes are not interchangeable. Organbidexka, above the Irati beech forest, is the great all-rounder, one of the three best sites in Western Europe for the sheer diversity of birds of prey, storks and cranes that cross it. Lizarrieta, in the bowl above Sare, is a key spot for red kites, cranes and wood pigeons pouring through lower down. Lindux, on the ridge at the Navarrese border, is counted every year by French and Navarrese ornithologists working together, and it regularly logs the highest raw totals of all, with single days of more than 20,000 cranes. Bird migration is a borderless affair.
Even without birds, these places are worth a visit. Birds just make it magical
Highway two: through the marshes
Not every bird crosses the mountains. Many follow the coast instead, and for a whole other group the coast is not a route but a destination, a place to stop, rest and refuel before the next leg. This is where the estuaries come in, and they are the part of the system that is internationally important.
At the mouth of the Bidasoa lies Txingudi, a wetland split neatly in two by the France–Spain border between Hendaye, Irun and Hondarribia. It is a Ramsar site and part of the Natura 2000 network, and more than 250 species of bird have been recorded there. Its heart is the Plaiaundi park, just 24 hectares of lagoons and tidal beach that were restored from a degraded, half-drained state in 1988 and now pull in spoonbills, waders and herons. Further west, near Gernika, the Urdaibai estuary is a UNESCO Biosphere Reserve and the largest wetland in the Basque Country, home to a research centre run by the Aranzadi science society that ranks among the references for bird study in Europe.
One of the birds that stops to refuel in them is the aquatic warbler, a small, streaky, unremarkable-looking reed bird that happens to be one of the rarest and most threatened migratory songbirds in mainland Europe. Its entire world population, perhaps 11,000 singing males, breeds in the marshes of just four countries in Eastern Europe: Belarus, Ukraine, Poland and Lithuania. Every autumn it flies the width of the continent to winter in West Africa, and ringing studies have shown that the wetlands of the southeast Bay of Biscay, the Adour, Txingudi and Urdaibai, are among the refuelling stops it depends on along the way. A bird from a Belarusian march, feeding in a Basque marsh, on its way to Senegal.
The Wetlands of Urdaibai Biosphere Reserve
Highway three: out at sea
Stand on the shore and look out over the Bay of Biscay, and a third migration is passing that most people never think of as migration at all. The bay is one of the most important stretches of sea for birds in the whole northeast Atlantic. In autumn, gannets stream past the headlands in long lines, plunging for fish. Shearwaters of several kinds, Cory’s, great, sooty and Manx, sweep low over the swell. Tiny storm-petrels flutter over the water like bats, and skuas chase the gulls to rob them.
The star of this highway is the Balearic shearwater, a dusky, fast-flying seabird that is critically endangered, one of the most threatened seabirds in Europe. It breeds only on islands in the western Mediterranean, and after breeding it leaves the Mediterranean entirely and comes out into the Atlantic, with the Bay of Biscay as one of its main areas to moult and feed before the return. Modern tracking with GPS tags shows that gannets and Balearic shearwaters both follow this coast closely on their way between Biscay and West Africa, some adult gannets passing through the waters of as many as ten countries in a single journey. All of it happening a mile or two off beaches where people are swimming.
Why having all three matters
Any one of these would put a place on the birdwatching map. A top-three raptor pass would do it. Two internationally protected estuaries feeding a globally threatened songbird would do it. A major seabird corridor would do it. The Basque Country has all three, within about fifty kilometres of each other, meeting where the mountains, the wetlands and the sea come together in a very small space.
That compression is the real distinction. It is not that any single Basque site beats Gibraltar or Falsterbo on numbers. It is that nowhere else packs this many different migration systems so tightly. A single autumn day here can hold an eagle crossing a mountain, a rare warbler hiding in a reedbed, and a shearwater cutting across the waves, and you could in principle see all three before lunch.
One flyway, one territory
There is a quieter point running underneath all of this. The birds treat the whole area as one place. The frontier that runs through the middle of Txingudi, that separates the French passes from the Navarrese ones, that divides the coast into national waters, means nothing to a crane or a warbler or a gannet. They use the mountains, marshes and sea of the Basque Country as a single connected system, because ecologically that is exactly what it is.
The people who study and protect it have had to work the same way. The mountain counts are run jointly across the French–Navarrese border. Txingudi is managed by a cross-border consortium that brings together Hendaye, Irun and Hondarribia, and was even given a shared Basque name to build a common identity across the frontier. The wetland science that tracks the aquatic warbler spans sites in both states. Migrating birds are connecting Ipparalde and Hegoalde, the Northern (French) and Southern (Spanish) Basque Country.
Map of Euskal Herria — The Spanish & French Basque Country
A chain is only as strong as its links
Bird migration connects land, sea, marshes and ecosystems, from Europe to Africa. It also means that such a connected system can be broken by breaking one link. Migration on this scale only works if every stage still works. Once migration routes are broken, they probably cannot be repaired. A warbler that arrives at a drained marsh does not shrug and fly to the next country. It runs out of fuel.
The pressures are real and local. The Txingudi marshes sit hemmed in by a city, a motorway and an airport. Out at sea, the small fish that seabirds live on are shifting north as the water warms, and the birds that depend on them, like the shearwaters, are being pulled along with their food. This is why the reserves, the counts and the protected designations are not bureaucratic detail. They are what keep the individual links intact so the whole chain can still carry a continent’s birds from the north of Europe to Africa and back.
The best crossroads you have never heard of
Put it all together and the Basque Country is not just a nice place to watch birds. It is one of the decisive junctions on the western edge of Europe, a place where the mountain, the marsh and the sea each carry their own migration and all three cross at once. You can stand anywhere in the Basque Country and a good share of moving birds in Europe pass by above and beside you.
In the next article we come down from the map to the ground: where you can actually go to see all of this for yourself, when to go, and how you can take part and help.
