Dialects in short songs of yellow-rumped (Cacicus cela) and red-rumped caciques (Cacicus haemorrhous): evolution and discrimination at the colony level

International audienceA field study has been conducted in French Guiana since 2005, by recording “short songs” of male yellow-rumped and red-rumped caciques. This is a rare field study on Neotropical birdsong, focusing on the Icterid family, a very good model to study the evolution of birdsong in relation with sociality. Short songs are involved in male-male communication in these two colonial multi-male / multi-female species. We found dialects characterized by time and frequency parameters in male short songs in both species. This is the first description for such song and dialect in male red-rumped caciques. We analyzed the temporal evolution of these songs in the two species, over seven years at the same localities. We find dialects each year but the short songs’ frequency and time parameters vary from year to year. Playback experiments were also made at different colonies in 2012 for yellow-rumped caciques. We observed in reaction to the stimuli (familiar or unfamiliar song) neither alarm calls or flight, nor aggressive behavior toward the loudspeaker. We discuss the results in relation with hypotheses for the evolution of bird dialects, with a special focus on social influences on song plasticity