Arguin bank, Gironde, France

At the mouth of the Arcachon basin, between Cap-Ferret and the Pilat dune (the highest in France, 350 feet, or 106 m, high), the Arguin bank shows through the waters of the Atlantic Ocean. The site is made up of a group of sandy islets that change form and position according to marine winds and currents on a relatively regular cycle of some eighty years, varying the area from 375 to 1,200 acres (150 to 500 hectares). It was declared a nature reserve in 1972. The Arguin bank serves as a place for short stops, hibernation, or nesting for many migratory bird species. It primarily hosts a colony of 4,000 to 5,000 couples of sandwich terns (Sterna sanvicensis), one of the three largest in Europe. Despite its protected status, the nature reserve is threatened by growing crowds of tourists and the development of oyster farming on its periphery. Mauritania has a protected area with the same name, the Arguin Bank National Park, which also receives many colonies of migratory birds.