About 2,000 dead penguins have washed up on the coast of eastern Uruguay in the past 10 days, and the cause is a mystery.
Bird flu has been ruled out by environmental authorities after the Magellanic penguins, mostly juveniles, died in the Atlantic Ocean and were carried by currents to Uruguayan shores.
“This is mortality in the water. Ninety per cent are young specimens that arrive without fat reserves and with empty stomachs,” Carmen Leizagoyen, head of the Environment Ministry's department of fauna, told the AFP agency,
She stressed that all samples taken have tested negative for avian influenza.
Magellanic penguins nest in southern Argentina. In the southern hemisphere winter, they migrate north in search of food and warmer waters, reaching the coast of the Brazilian state of Espirito Santo.
“It is normal for some percentage to die, but not these numbers,” Ms Leizagoyen said, recalling that a similar situation occurred last year in Brazil, for undetermined reasons.
Hector Caymaris, director of the Laguna de Rocha protected area, told AFP that he counted more than 500 dead penguins along 10km of Atlantic coast.
Environmental campaigners blame the increase in Magellanic penguin deaths on overfishing and illegal fishing.
“From the 1990s and 2000s, we began to see animals with a lack of food. The resource is overexploited,” said Richard Tesore, of SOS Marine Wildlife Rescue.
A subtropical cyclone in the Atlantic, which hit south-eastern Brazil in mid-July, probably killed the weakest birds, he said.
As well as penguins, Mr Tesore said he has also recently found dead petrels, albatrosses, seagulls, sea turtles and sea lions on the beaches of Maldonado, a department east of Uruguay's capital, Montevideo.