Effects of Eavesdropping on Subsequent Signalling Behaviours in Male Canaries

Signalling interactions could provide information for an observing third party. This behaviour has been labelled as eavesdropping. Studies on eavesdropping in birds have concerned only few species and have mainly been conducted in the wild. Our experiment was designed to evaluate the effects of eavesdropping on subsequent interactions in male canaries in a controlled laboratory context. The experiment had two stages: a presentation stage and a test stage. During the presentation stage, subjects heard three different interaction types: an alternating interaction, an overlapping interaction or two song sequences presented separately one after the other, i.e. without interaction. Then during the test stage, subjects were allowed to listen to the songs previously heard separately. We noted calls emitted by subjects during the two stages. During the presentation stage, responses of male canaries did not differ according to the type of interaction they could hear. During the test stage, we found a clear effect of the song status on the calls emitted by subjects. They emitted less calls during the songs of the winner than during all other songs. Surprisingly, subjects also produced intermediate responses by emitting fewer calls during the second song previously heard during the presentation phase, and during the song of the looser when compared to the three other songs. Our results show that male canaries obtain information on the relative threat from an overlapping interaction whereas an alternating interaction does not seem to provide any kind of relative information on singers’ status. In following encounters, the higher the potential threat of a singer was, the less the subjects emitted calls, probably to avoid the more serious rival. This inhibiting effect is discussed.