Cold water off Brazil might be causing Argentine penguin nest failures

November 27, 2000

Argentine penguins are turning up off the coast of Brazil in record numbers, and a University of Washington scientist believes it is because unusually prolonged cold water has kept their food supply - primarily sardines, anchovies and squid - farther north much longer than usual. The far-distant food supply could be a major culprit in penguin nest failures now occurring in Argentina.

It is not unusual for the annual migration of Magellanic penguins from Punta Tombo, a reserve in Patagonia on Argentina's Atlantic coast, to take them as far north as Brazil, said Dee Boersma, a UW zoology professor and director of the Magellanic Penguin Project. There have been several instances in which unusually cold currents drew the birds farther north than Rio de Janeiro.

"What's unusual is that there are so many of them and so many are going ashore. They are young birds, most of them aren't even a year old," Boersma said. "This is such a cold-water event, with so many fish, that the young have been doing well and surviving. Now they should be heading south, but some of the birds went so far north that they may have stayed longer than the fish did."

While young birds seem to do well in years when the cold water shows up, those same conditions appear to be taking a toll on the birds' reproduction this season. Birds were late in returning to Punta Tombo to breed, and not as many as usual are breeding. They started with 116 nests in September and laid their eggs at the end of October.

"This is the latest breeding season in the 18 years I've been studying penguins at Punta Tombo," Boersma said.

A week ago, her graduate students working in Argentina reported that of the 116 original nests only 39 had not been abandoned. "Some of the females had been sitting on nests for nearly three weeks and were so skinny they had no choice but to desert their eggs," she said.

Meanwhile, hundreds of these temperate-zone penguins, many of them starving, have come ashore in Brazil. Some have been rescued by biologists, but there are numerous reports of people keeping them as pets and even placing the flightless birds inside refrigerators to keep them more comfortable, a mistaken notion that is likely to cause hypothermia. In addition, many more dead penguins have washed up on Brazilian beaches.

Boersma speculates that these birds might have miscalculated where the fish were and had to come ashore. "Once the cold pockets of water off of Rio started to break up in September, some of the young birds probably got caught without food."

Boersma, her students and scientists from the New York-based Wildlife Conservation Society have banded more than 45,000 penguins to study their movements and behavior. In the last few years, she has attached satellite transmitters to a number of birds and discovered that they can range hundreds of miles in search of food. During the last 18 years, some of the banded penguins have been found dead on Brazilian beaches, with a larger-than-usual number of dead banded birds during the cold-water years of 1984, 1988, 1991 and 1992.

She cites evidence that, between 1961 and 1990, water surface temperatures were typically at least 1 degree colder than normal in July off the coast of southern Brazil, and notes that the cold water extends even farther north this year. The more frigid waters might have been enough to keep their food supply farther north longer than normal.

That means the penguins that remained at nests in Punta Tombo have had to forage much farther north. Some male penguins are as much as 400 miles away from their nest site at a time when they should return to provide food for newly hatched chicks. Instead, Boersma said, many of the nests at Punta Tombo are failing because it is taking the adult penguins so long to return.

A female penguin stays on the nest and fasts while the male goes for food. Typically the male is gone about two weeks before returning for nest-tending duties and to let the female end her fast. This year, because of the distances involved, the males' timing has been thrown off, and by the time they return many of the females have gotten too thin and have abandoned their nests.

This is just the latest setback for the Punta Tombo penguins, which also have suffered from pollution, overfishing that reduces their food supply, and possibly because of climate change. Just a year ago, Boersma noted, two days of torrential rains associated with an El Niño-style phenomenon killed 85 percent of the new penguin chicks.

"Magellanic penguins have been declining about 2 percent a year for the last 13 years," she said. "Penguins are sending a signal that climate change is here. The irony is that cold years are saving the population. Even though breeding success will be low this year, the survival of last year's young will be high and that means in three to five years these young will be back to breed. All in all, young penguins in Brazil is a good thing."
-end-
For additional information, contact Boersma at 206-616-2185 or boersma@u.washington.edu

University of Washington

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