The Lac du Der has become a paradise for migratory and sedentary birds. More than 300 species have been counted and their numbers are increasing. Every year, at the beginning of November, the lake is almost empty. All that remains is the dead band, which is the minimum volume of water necessary for the survival of the fish. The lake thus develops into huge mudflats which attract many birds and provide them with abundant food. Along with the surrounding fields and forests, the migratory birds are able to find all the food they need to regain their strength on their journey to the Mediterranean.