Perhaps no birds have a real nature so at odds with the way most people think of them. Rather than fluffy ambassadors of good cheer, these birds are tough, dense, efficient deepwater predators, much more likely to bite you (hard!) or whack you with a flipper than cuddle or shake your hand. The contour feathers are reduced to a continuous layer of stiff scales, and with the least-pneumatized bones of any bird, penguins are no-nonsense underwater flying machines, flapping their strong flippers to propel themselves, often to great depths, in pursuit of their prey. Limited to high-productivity ocean environments of the Southern Hemisphere, even species that nest at the equator are reliant on the upwelling of nutrient-rich cold currents.