The signal value of birdsong: empirical evidence suggests song overlapping is a signal

Please cite this article in press as: Naguib, a signal, Animal Behaviour (2010), doi:10.10 Birdsong is among the most well-studied communication systems in vertebrates and provides many textbook examples in animal behaviour, ecology and evolution. Owing to the substantial body of research dealing with this topic, and the numerous research groups focusing on different aspects of birdsong, it is often difficult to maintain an overview across the discipline. An increasing number of reviews on various aspects of birdsong provide important syntheses (Todt & Naguib 2000; Vehrencamp 2000; Gil & Gahr 2002; Beecher & Brenowitz 2005; Catchpole & Slater 2008). The recent review by Searcy & Beecher (2009) makes a valuable contribution by bringing together a substantial body of research on the territorial function of birdsong with a specific focus on singing contests. The review covers a large body of research and critically discusses the evidence that certain components of singing contests act as aggressive signals. Furthermore, it places many ideas in a context that will stimulate researchers to conduct more advanced studies and to plan carefully which behavioural responses to measure.