Birds like murres helped researchers understand why penguins no longer fly. Penguins are excellent swimmers. But even with wings, the aquatic flightless birds do not take to the skies despite having wing-like flippers. In fact, a new study says that penguins became so good at swimming that they eventually evolved to specialize at that skill at the cost of airborne flight. "Like many people, I've always been interested in penguins, and seeing them do these phenomenal marches across the ice, I've often thought: 'Why don't they just fly?' Professor John Speakman, from the University of Aberdeen and the Chinese Academy of Sciences said." And it's really great to be involved in the group of people that have solved it."
The new study says that at least five species of penguin have adapted into flightless birds. In particular, biomechanical models of energy costs during flying and diving suggest that a wing designed for optimal diving performance should lead to enormous energy costs when flying in air,” explains the study. “Costs of flying and diving have been measured in free-living animals that use their wings to fly or to propel their dives, but not both.”
Many studies compare penguins’ underwater prowess to being like flight beneath the waves. They can swim at speeds up to 8mph over a distance of 100 miles, and up to six times faster when under duress. While most penguins catch their food near the water’s surface, some Emperor penguins have been known to dive 1,870 feet for more than 20 minutes. "Basically the hypothesis is that as the wings became more and more efficient for them to dive, they became less and less efficient for them to fly,” Speakman said. "At some point it became so 'expensive' for them to fly, that it was better to give up flying altogether and make the wings into small flippers."
Speakman and his colleagues studied one bird that can both swim and fly: the guillemot. “These birds have these very short wings and they have to beat them at an incredible speed to stay in the air,” Speakman said. However, while the seabirds look very similar to their penguin counterparts and are nearly as good at swimming, they are barely functional at flying. "The energy costs are very, very high,” Speakman said. “These birds have these very short wings and they have to beat them at an incredible speed to stay in the air. It is exhausting for them.” Another species of seabird, the Murres, is also capable of flight.