However, they evolved to become superb divers, and in the process lost the power of flight. A flying bird has to minimise its weight. For example, all flying birds have hollow bones. In contrast, to be a successful diver a penguin wants to keep it's weight high, so they have solid bones. Penguins are excellent divers, they can dive to depths of 1000m and remain down for up to 20 minutes.
All penguins use sounds to communicate.
Chicks in large colonies need to be able to attract their own parents so that they can be fed, adults need to recognise one another when they come back from fishing trips, etc. Different species make different noises. Their chicks, in contrast, make a high pitched whistling noise to demand feeding. The Chinstrap has a shrill, screaming voice, so loud that it is sometimes called the stone-cracker penguin. The King penguin makes a trumpeting sound.