Abstract
Following the publication of this article, the authors noted the following errors:
Two authors were omitted from the author list. The correct and complete author names appear above. The affiliation for Drs Vignal and Mathevon is the Université de St-Etienne, CNRS, ENES/CNPS UMR8195, Saint-Etienne, France. The grants should have included the following note: ‘These experiments were supported by the Program ‘Emergence’ of the Région Rhône-Alpes and the Agence Nationale de la Recherche (Project ‘Birds’ voices, ANR-06-BLAN-0293-01)’.