Abstract
Individual recognition by voice in colonial birds has to face the acoustic properties of the colonial environment, which is a medium difficult to penetrate, and where sound propagation appears random. We examined two parameters of the communication system in penguins, in relation to the degree of coloniality of the species : first the signalling posture, with the beak directed upwards in all species except for Emperor penguins that outstandingly directs its beak downwards ; second the structure of the identification signal, characterized by a beat phenomenon in Emperor and King penguins. Within the context of the search for the partner or the chick, it appeared that signalling posture and sound structure were all the more sophisticated that the sound transmission was difficult. The extreme example was illustrated by the Emperor penguin in which colonies consist in dense flocks where birds move around. The outstanding signalling posture of emperors beams the signal forward, so that sound energy is directed in the direction of the moves during the search for partner or chick. The individually -distinctive beat is redundant and not degraded by the sound-scattering and noisy environment of the colony. This suggests that the acoustic constraints of the colonial environment shaped the parameters of the communication systems of penguins to fit into their communication strategies.
Published Version
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