In the king penguin (Aptenodytes patagonicus), both pair members alternate in incubating and rearing their chick. Mates can recognize each other among thousands of other birds in the hubbub of the colony using only acoustic signalling: the display call. Large penguin colonies are found on sub–Antarctic islands where strong winds blow throughout the year. We have shown by experiments under natural conditions that the level of background noise increases in windy conditions and thus leads to a diminution of the signal–to–noise ratio. Moreover the emergence level of the signal revealed by entropy calculation is statistically weaker in windy conditions. To achieve breeding success, birds must continue communicating in spite of the significant decrease in the total amount of information that can be transmitted in windy situations. For the first time, to our knowledge, we have shown that a bird species takes into account the constraints imposed by wind on their acoustic communication. In windy conditions, birds try to maintain the efficiency of communication by increasing both the number of calls emitted and the number of syllables per call. This result conforms with predictions from the mathematical theory of communication: increased redundancy in a signal improves the probability of receiving a message in a noisy channel.