Penguin

Like many birds, penguins must travel a long way between their feeding and breeding grounds. But rather than fly, they swim. It is a hard journey that has left biologists scratching their heads over why the birds did not keep their ability to fly as their diving ability evolved. A new study argues that birds cannot be both masterful divers and flyers, because flying abilities must weaken as the animals adapt to diving.

Rather than looking at penguins, a team led by biologist Kyle Elliott at the University of Manitoba in Winnipeg, Canada, examined species of diving seabirds that still have some ability to fly. These included the pelagic cormorant (Phalacrocorax pelagicus), a species that propels itself underwater with webbed feet, and the thick-billed murre (Uria lomvia), which flaps its wings underwater to swim.

The researchers tagged murres with recorders that measured the time of dives as well as depth and temperature, and cormorants with data-loggers that measured depth, tempe