Human influences, global warming, fishing and petroleum pollution lower breeding success of penguins

03 Jul 2008

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Biologist P. Dee Boersma of the University of Washington has been a watching the Magellanic penguins at Punta Tombo in Argentina for around 30 years, and says that for around that time, their population has been shrinking alarmingly.

The breeding pairs are down 22 per cent since 1987, she says in the latest issue of BioScience, as a consequence of damage to their environment on account of overfishing, pollution from offshore oil operations, and shipping. Oil spills off the South American coast off Uruguay, Argentina and Brazil have also contributed to the Punta Tumbo declines, says Dr Boersma.

Adding to those man made causes, says Dr Boersma, is climate change. She says global warming is the latest contributor to reducing sea ice, and thereofore reducing the abundance of the marine creatures the birds feed on. Magellanic penguins are capable of swimming almost a 100 miles a day, but now the need to forage for food 40 miles farther from their nests than they had to a 10 years ago.

Dr Boersma says that though some part of the food shortage is fishing-related, climate change is also a growing factor as glaciers and sea ice retreat. She says, ''even small variations can have major consequences for penguins.''

Magellanic penguins inhabit the Falkland Islands and the coasts of Argentina and Chile. The Punta Tombo colony, Dr Boersma's workplace for almost three decades is possibly the largest, accounting for around 200,000 breeding pairs. Magellanic penguins are around 27 inches tall, weighing around 10 to 12 pounds, and their breeding period is between late September and February.

Though females usually produce two eggs, parents typically favour the first-hatched chick unless food supplies are abundant,and often the latter born does not survive.

Environmentalists say that dwindling penguin numbers is a sign that the world's oceans are in trouble. Scientists agree on the existence of around 19 species of penguins, of which around a dozen are in some form of trouble according to Dr Boersma.

The International Union for the Conservation of Nature lists three penguin species as endangered, seven as vulnerable, which translates as "facing a high risk of extinction in the wild," and another two as "near threatened."

Experts say just 15 years ago, only five or seven species were vulnerable. The US Fish and Wildlife Service has one species of penguin listed on its endangered list, and is mulling adding another 10.

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