July 1 (Bloomberg) -- Penguin colonies are collapsing because global warming, pollution and over-fishing are damaging their ocean habitat in the southern hemisphere, a researcher at the University of Washington said.

Penguins are serving as a ``canary in the coal mine,'' and their declining numbers are evidence that people are altering the animals' environment, said Dee Boersma, a biology professor at the Seattle-based university, in a preview of the study that will be published in the July/August edition of the U.S. journal BioScience.

Populations of the flightless bird have declined by half over the past three decades in Argentina, while in southern Africa the number of penguins fell to about 63,000 from a peak of 1.5 million animals a century ago, the research showed. Fish species eaten by penguins are becoming scarce as people consume more seafood and global warming changes ocean currents.

``It's clear that humans have changed the face of the Earth and we have changed the face of the oceans,'' Boersma said in a statement. ``The Discovery Channel and public television are very popular for their nature programs, and those featuring penguins are especially popular. But we don't want to just have them in our television sets.''

Unstable ice in the Antarctic broke up earlier than normal in 2006, forcing two-month-old chicks that couldn't survive the cold water to swim, Boersma said. The animals, featured in the film ``March of the Penguins'' a year earlier, probably suffered from a colony-wide breeding failure, she added.

The risk to penguins from oil pollution is also increasing as they stray farther from their traditional habitats in search of food, the study said.

To contact the reporter on this story: Jeremy van Loon in Berlin at jvanloon@bloomberg.net.

Last Updated: July 1, 2008 02:09 EDT