Nightingales respond more strongly to vocal leaders of simulated dyadic interactions

Although vocal interactions in songbirds have been well studied, little is known about the extent to which birds attend to their conspecifics' interactions. Attending to others' interactions can provide valuable information since vocal interactions are often asymmetrical and can reflect differences in the state or quality of the signallers. Playback experiments with simulated dyadic interactions showed that male territorial nightingales (Luscinia megarhynchos) attend to asymmetries in interactions and respond more strongly to rivals that overlap the songs of their counterpart. In order to test if nightingales respond differently to two interacting rivals that are alternating songs asymmetrically (with leader-follower roles), we simulated an interaction using a dual-speaker design. Subjects discriminated between the simulated singing strategies and responded more intensely at the loudspeaker playing the preceding songs. This suggests that individuals whose songs precede in an interaction when there is no acoustic overlap are perceived as more serious rivals. Intense responses to the preceding songs compared with intense responses to the overlapping (non-preceding) songs in a previous study also indicate that discrimination is not the result of one specific proximate cue such as greater attention to the first- or last-heard stimulus. Thus, these results provide further evidence that by listening to asymmetries in conspecifics' vocal interactions, receivers can obtain valuable information on their relative differences.