The following article, reprinted courtesy of the Boston Globe, gives some background information that teachers will find help in the Chick Die-off activity.

Naturalist Roger Tory Peterson calls the black and white birds "the litmus paper of the sea." Biologist Susan Trivelpiece calls them "canaries in a coal mine." To gauge the health of the southern oceans, and of our whole watery planet, many look to the 24 million penguins in these waters.

This year, Australian scientists saw something alarming: a massive chick die-off in some colonies of Adelie penguins. On one Antarctic island near the Mawson base, scientists said 50 chicks were starving to death each day.

"We've never seen anything like this before," one scientist told New Scientist magazine, attributing the deaths to the lack of krill - small, shrimplike organisms.

But the shortage was spotty. Penguins in an area being studied by Trivelpiece had plenty to eat.

Adelie penguins at colonies near the US Palmer Station on the peninsula, though, were also having difficulties finding food. Parents were taking 24-hour foraging trips, rather than the usual eight hours, said Bill Fraser, another biologist, from Montana State University.

The chicks were skinnier, but they did not die-off, said Fraser, in an E-mail message.

Biologists are just now beginning to understand the complexities of the Antarctic marine ecosystem. Much of the penguins' success depends on the one defining element in the Antarctic - ice.

The krill are produced in big numbers during years with a heavy sea-ice cover. But because penguins feed on krill that are several years old, shortages do not develop until several years after a bad season.

This year's krill shortage was the worst Fraser has seen, he said. He said another factor - a later than usual explosion of the plankton that attracts krill - probably combined with the shortage to hit penguins with "a double dose of bad luck."

Scientists say it's too early to judge whether the penguins are being affected by warmer temperatures or the ozone hole above. So far, the population fluctuations may be normal.

As a species, says Trivelpiece, "Penguins aren't in peril by any means."

Usha Lee McFarling