Banc d'Arguin holds the largest gathering of wintering shorebirds anywhere on the East Atlantic Flyway, the migration route that runs down the Atlantic coasts of Europe and Africa: around two million waders crowd its tidal flats each winter. More than two-thirds of the world's bar-tailed godwits and half its red knots are among them. The park sits on Mauritania's central coast, where the Sahara runs straight into the Atlantic and cold, nutrient-rich water wells up from the deep, feeding one of the richest fish nurseries on Earth. Dunlin, godwits and knots that breed in the Arctic and Siberia fly the length of Europe and West Africa to winter on these shallow banks, packed so densely that the flocks show up as dark, shifting ribbons on satellite images. Declared a UNESCO World Heritage Site in 1989, its roughly 12,000 square kilometres of lagoons, sandbanks and low dune islands are now twinned with the Wadden Sea at the far end of the same flyway.
The Imraguen people still fish these waters under sail, one of the last communities anywhere to do so. They work from broad wooden boats called lanches, hauling in mullet by methods handed down for generations. By tradition they also whistle to call in wild dolphins, which drive the fish toward their nets. Access is deliberately hard: the park is entered only with a permit and a guide, usually from the village of Iwik, and much of it can be reached only by boat. From a dune crest at Cap Tafarit you take in the whole bank at once, turquoise channels winding between pale sandbanks. Down at the water it is wind and silence, broken by the roar of thousands of birds lifting off the flats together. Come between November and March for the full spectacle; outside that window the great wader flocks have scattered north, though flamingos, pelicans and the fishermen remain.