Finding one's mate in a king penguin colony: Efficiency of acoustic communication

In the king penguin, during the three months of incubation and the brooding stage, members of a pair alternate care duties on land with foraging trips . Contrary to most of the species of birds that nest at a fixed location, t he king penguin carries its egg on its feet during incubation. This allows the incubating parents to move in the colony. Brooding or incubating parent s moved on average 4.4 meters between egg-laying and the end of the broodin g stage. This movement in a group of thousands of other birds reduced the r eliability of visual cues for recovering the pair mate during the change-ov er. We showed that the difficulty in relocating the mate was more important during the brooding stage than during incubating. We confirmed earlier findings that acoustic communication was the main mode of communication during a change-over, and showed that the omnidirectional properties of sound allowed birds to reach more than five hundred other bi rds with each emitted call. Our experiments proved that the communication s ystem is performed at short or medium range. On average, the birds identifi ed their mate at a distance of 8.8 m. Seventy percent of the birds started the acoustic search of their mate when the distance was shorter or equal to this discrimination range, and so acoustic communication is a particularly efficient strategy in the king penguin.