Why penguins dumped flight for flippers

The thick-billed murre is a diving bird that flies - just not very well. In fact, when Robert Ricklefs at the University of Missouri at St Louis and his colleagues studied 41 murres in flight, they found the birds consumed 146 watts per kilogram of body weight.

http://www.newscientist.com/article/dn23572-why-penguins-dumped-flight-for-flippers.html?cmpid=RSS%7CNSNS%7C2012-GLOBAL%7Conline-news