UMSL biologist Robert Ricklefs was part of a research team that studied two species of seabirds to help shed light on why penguins lost their ability to fly. Their findings were published in the “Proceedings of the National Academy of Sciences.” (Photo by August Jennewein)

Why don’t penguins fly?

A new study bolsters the widely-held theory that penguins abandoned flight in order to evolve into accomplished swimmers.

Flying is a speedier mode of transportation. So, why give it up for a flightless existence? To help solve the mystery a team of researchers examined two diving seabird species that still have some ability to fly – the thick-billed murres, which are wing-propelled divers, and the pelagic cormorant, which are foot-propelled divers.

The researchers, including Robert Ricklefs, Curators’ Professor of Biology at the University of Missouri–St. Louis, found that both cormorants and murres must spend exceedingly large amounts of energy to fly.

“Biomechanical models of energy costs during flying and diving suggest that a wing designed for optimal diving performance should lead to enormous energy costs when flying in air,” the authors wrote in a paper published in the “Proceedings of the National Academy of Sciences.”

The findings suggest that birds are designed to do one or the other – fly or swim – and as they adapt to diving their flying abilities weaken.

“Basically, they have to reduce their wings or grow larger to improve their diving, and both would make flying impossible,” Ricklefs told Nature. “To be an efficient swimmer you want a wing that is more like an oar — that makes it impossible to fly,” he explained to NBC News.

He said the main message from their research is compromise.

“You can’t have a wing that’s both good for propulsion in water and in air,” he told New Scientist.

Articles on the study were also published by BBC, Wired.co.uk, Discovery News, Scientific American, LiveScience, Deccan Herald (Bangalore, India) and Yahoo! News.