How Penguins Lost Their Ability to Fly

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Penguins lost their ability to fly millions of years ago, and now a new study explains why -- the birds became lean and mean diving machines, trading flight for such skills.

The study, published in the latest Proceedings of the National Academy of Sciences, points out that good flippers don’t fly very well.

"Once penguins gave up flight, changes to wing structure and overall body size and shape probably followed rapidly because flying no longer placed constraints to body form," co-author Robert Ricklefs told Discovery News.

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"Note that penguins are much more at risk of predation in the water than they are on land, and so there has been strong selection to make their swimming and diving as efficient as possible," added Ricklefs, who is a professor of biology at the University of Missouri at St. Louis.

Ricklefs, lead author Kyle Elliott and their team at first wondered why the ubiquitous black and white birds lost their ability to fly millions of years ago, given how beneficial flying can be. Emperor penguins laboriously walk over 32 miles between their rookeries and the sea. The journey takes them several days, which could be reduced to just a few hours if they could fly. Why then don’t they?

To solve the mystery, the researchers focused on birds-- especially the murre -- that both fly and dive. The scientists equipped 41 such wild-caught birds with equipment to measure avian energy expenditure. In doing so, the researchers came up with a new world’s record. Murres and pelagic cormorants turn out to have the highest expenditure ever recorded for any flying animal.

"The costs are incurred in providing lift in air," Ricklefs explained, adding that overcoming drag in the air is also energy costly to the birds.

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