National Geographic Channel
During the Antarctic winter the South Pole becomes the coldest place on the planet. Temperatures regularly plummet to minus 60° Fahrenheit (minus 50° Celsius), prompting most of the 9,000 species of birds that cross the continent to hightail it for warmer climes.
Only one birdthe emperor penguinwill winter on Antarctica and use the frozen continent as a nursery. When the winds really start howling, the birds march inland by the thousands, creating 40 or so breeding colonies on the sea ice along the edge of the continent.
"This is an animal that does things in extremes," said Paul Ponganis, a research physiologist at the Scripps Institute of Oceanography in San Diego. Ponganis has studied penguins for over a decade. "Emperors can fast for extreme amounts of time and dive to extreme depths, which allows them to live in a very extreme place."
Emperor penguins are veritable sea bulletsthey can zoom to a depth of 1,500 feet (500 meters) to feed, holding their breath for as long as 22 minutes. That allows the penguins to exploit resources other birds can't.
Working from his gale-proof base at the McMurdo Station on Ross Island, just off the Antarctic continent, Ponganis tags along on some of the penguins' dives by corralling a few of them and attaching miniature video recorders to their backs. Other bite-sized gadgets measure the penguin's oxygen levels, heartbeat, and temperature.
"Penguins are as well designed for underwater flight as birds are for flying in the air," Ponganis said. "And when they swim, they really are flying underwater. A penguin's wings act the same while it's swimming as a bird's does while it's flying."
However, a penguin's strokes are even more efficient. "Emperors can exert propulsion on both the upstroke and downstroke, while most other birds only exert pressure on the downstroke [during flight]," said David Ainley, an ecologist at H.T. Harvey and Associates, a biological consulting firm in San Jose, California. Ainley has studied Antarctic birds for over 20 years.
Long glides to the surface probably help emperor penguins conserve energy during their deepest dives. Another key is their solid bones. While skybound birds have evolved hollow bones to lighten their weight, penguins gradually lost that internal airspacedecreasing their buoyancy so they can plumb the depths.
Even then, emperor penguins never get wet.
Their outer feathers are flat, well oiled, and watertight. There is an air space between those feathers and the bird's skin that water never penetrates, keeping them from turning into icicles in the black Antarctic sea. "They have the highest feather density of any bird, about a hundred feathers per square inch (6.5 square centimeters)," Ainley said.
Life in the Icebox