Far-off food puts vast penguin colony under threat
Growing distance between nesting and feeding sites reduces chances of breeding successfully, say researchers
The Independent, Feb. 9, 2009
One of the largest penguin colonies in the world is under threat because the birds are being forced to swim further to find food.
Magellanic penguins living in the Punta Tombo colony on the coast of Argentina are feeding 25 miles further from their nesting sites than they did only a decade ago, according to scientists who attached satellite tags to the birds.
The extra distance spent searching for food during the breeding season takes its toll on the penguins and reduces their chances of having young, said Dr Dee Boersma at the University of Washington.
"That distance might not sound like much, but they also have to swim another 25 miles back, and they are swimming that extra 50 miles while their mates are back at the breeding grounds, sitting on a nest and starving," she added.
The colony has already declined by a fifth in the past 22 years, and now numbers 200,000 breeding pairs of penguins. Of the 17 species of penguins, 12 are experiencing rapid population declines.
Boersma has studied penguin colonies for the past 25 years and tracks their movements by attaching satellite tags to the animals' backs. While the penguins are incubating an egg, they can swim 270 miles looking for food and be at sea for two to three weeks.
The birds' changing behaviour appears to be driven by changes in the environment, including overfishing, which is reducing local stocks of anchovies, and the return of large predators such as foxes and pumas that have previously been controlled by rangers.
"Penguins are having trouble with food on their wintering grounds and if that happens they're not going to come back to their breeding grounds," said Boersma. "If we continue to fish down the food chain and take smaller and smaller fish like anchovies, there won't be anything left for penguins."
Magellanic penguins nest in burrows and at Punta Tombo they are frequently flooded by rainstorms that can kill small chicks. Analysis of the penguins' movements showed many are moving to colonies up to 250 miles farther north.