More than 1,000 penguins were found dead on the shores of southern Chile last weekend, reports Australia's Brisbane Times (and noted by ProMED-mail). The reason for the large die-off remains a mystery. The birds, which were both Magellanic (Spheniscus magellanicus) and Humboldt (Spheniscus humboldti) penguins according to reports, are native to the waters around southern Chile and Argentina and migrate north for the Southern Hemisphere's winter.

"With that number," says P. Dee Boersma, a professor of biology at the University of Washington in Seattle, "it seems like a lot to be caught in a net." Although fishing nets are an occasional killer, it's more common that just a few will be caught at a time, she says. And after seeing television coverage of the birds while in Argentina, she notes that, "They didn't look oiled," (coated from an oil spill, which can break down the coating on their feathers, exposing them to chilly waters). They also don't appear to have been poisoned, Chilean Navy Lt. Rodrigo Zambrano told The Patagonia Times.

Boersma, who is also the director of the Magellanic Penguin Project in Punta Tombo, Argentina, hazards that the penguins might have actually been poisoned by a toxic algae bloom (common in the South American autumn). A winter algae bloom killed thousands of penguins off the coast of Argentina in 2000, she notes. Some of the recently discovered dead penguins have been sent to nearby University of Valdivia for analysis.

But don't count on an answer soon – or ever, cautions Boersma. To detect traces of chemicals from an algae bloom, the specimens must be recently dead because telltale chemical clues "dissipate really quickly," she explains.

In December, seven penguin species were put on the endangered species list, although neither the Magellanic nor Humboldt was among them. Scientists attribute the threat of extinction largely to climate change, as ice melts away and changes the penguins' habitat and food supply. A study published in the Proceedings of the National Academy of Sciences in January found that if ice in Antarctica changes at the predicted rate, the emperor penguin will be nearly extinct by the end of this century.

Image of Magellanic penguins courtesy of reurinkjan via Flickr