1. Centre d'Ecologie Fonctionnelle et Evolutive; UMR 5175 - CNRS; Montpellier Cedex 5; France
2. Department of Zoology; Faculty of Science; Charles University in Prague; Praha 2; Czech Republic
3. Department of Population Biology; Institute of Vertebrate Biology; Academy of Sciences of the Czech Republic; Brno; Czech Republic
4. Les Marais du Vigueirat; Arles; France
5. Office National de la Chasse et de la Faune Sauvage; CNERA Avifaune Migratrice; Arles; France