Global warming sees predator gulls thrive and pose threat to penguins
Late summers spark rise in predator gull numbers in Chile bird paradise
Magdalena Island, near Chile's southern tip, is a natural paradise for tens of thousands of penguins that come every year to breed.
Yet global warming could threaten the long-term survival of the species, say experts at the island nature reserve in the Strait of Magellan, about 50 kilometres from the city of Punta Arenas.
The island is home to 22 bird species - 11 that nest all the year round and 11 seasonal visitors - including Magellanic penguins.
About 23,000 tourists a year make the pilgrimage to Los Pinguinos Natural Monument, a protected area comprising tiny Marta Island and windswept Magdalena Island.
The penguins' main predators were aggressive seabirds called skuas and Dominican gulls, which feed on penguin eggs and young, says Roberto Fernandez, a ranger at the site.
Right now, the population of these predators was growing.
"We are seeing summer starting late, then lasting through into March; climate change is bringing about a rise in gull numbers," says monument administrator Neftali Aroca.
"You would have to undertake a long-term study in order to link this increase with a reduction in the penguin population, but the forecast is that in the future, the penguins could be at risk."
The worrying prognosis seems to confirm fears raised in January in a study published in the scientific journal PLOS ONE, which indicated that extreme weather conditions, such as unseasonable warmth and heavy rainfall, may have killed off a considerable number of young Magellanic penguins.
The study - conducted over 27 years in Argentina's Punta Tombo peninsula, the largest breeding ground for the species - showed that, on average, 65 per cent of the colony's young died annually, 40 per cent from hunger and 7 per cent because of the effects of climate change.
Each year, the penguins flee the cold to spend winter in the warmer waters off Brazil. As soon as they are big enough to swim, they head off on a 4,000-kilometre journey from Magdalena Island to Brazil.
They spend the Southern Hemisphere winter on the coast of Brazil's southern Santa Catarina state - though they sometimes make it as far up as Rio de Janeiro's beaches.
From mid-August, they begin to head back, via Uruguay and Argentina to the Strait of Magellan, the natural passage between the Atlantic and Pacific oceans, and Magdalena Island.
"Magellanic penguins come to the island to complete their reproductive cycle," says Valeria Sanchez, who has spent five years as a tour guide here. "
They start arriving in September, as summer approaches, to enjoy the longer days necessary to incubate their eggs and look after their young."
Magellanic penguins, which can live up to 25 years, are monogamous and share their lives with only one partner.
First to arrive on Magdalena Island are the males, who must seek out the burrowed nests dug the previous season and make any necessary changes with whatever material they can find, including stones and feathers, before attracting their mate.
About a fortnight later, the females arrive, and their keen partners sound a trumpet-like call to guide them to the nest.
After fertilisation, the female penguin lays one or two eggs; for the first 12days, she will incubate them and not leave them - even to eat.
Following their long fast, the mothers give way to the males so they can feed. The couples switch at roughly fortnightly intervals until the end of the 40-to-45-day incubation period ahead of hatching in around November.
"Between February and March, they start to leave the island, but this year they began leaving two or three weeks earlier," Sanchez says.