Giant iceberg blocks food source for penguins
Tens of thousands of penguin chicks could starve to death in the Antarctic over the next few weeks because the southern continents biggest iceberg is cutting off their parents from the sea and customary food supplies, according to New Zealand scientists.
Adelie penguins who have laid their eggs in rookeries on Ross Island normally have to walk no more than five kilometres to open water to get food for their chicks, but the iceberg known as B-15 now forces them to undertake an overland journey of 100km or more.
By that time, they have used up the food they store in their crops and there is none left to regurgitate for their youngsters.
The adult penguins, who spend winter on the edge of the sea ice, return to their usual nesting grounds every spring to lay an average of two eggs. They then take it in turns to make about 40 trips back to the sea to get food while raising the chicks.
Scientist John Cockrem, of New Zealand’s Massey University, an expert on penguins who has just returned from Antarctica, said that a survey indicated up to 50 000 breeding pairs may be affected.
But with a total population of two to three million Adelies of breeding age in Antarctica there is no risk to survival of the most common species of penguin.
Cockrem said two of three Adelie rookeries on Ross Island were affected, but open water next to the third and largest would ensure a normal breeding season for its birds.
“What’s happening is a natural phenomenon,” he said.
“If you consider the entire population of Adelie penguins in Antarctica, in terms of the species as a whole its a natural minor perturbation in one part of the species range.”
Cockrem said Adelie penguins, which normally stand 60-70cm high and weigh about 5,5kg, start breeding about the age of five and may breed for five to 10 seasons.
He said it was the second time in four years that the B-15 iceberg at 3 000sq km the worlds biggest floating object had affected the penguin breeding season by not breaking up enough to let them reach their nesting grounds easily.
“Naturally, in some years the ice conditions will be better than in other years, so the actual breeding success in a particular rookery can fluctuate quite a lot from year to year.
“But if the breeding of rookeries on Ross Island was impeded consistently over a number of years those rookeries would decline.”
But Cockrem said the number of Adelie birds in the region as a whole had been steadily increasing over the last decade or so. He said progress of the iceberg was being monitored by satellite as it moved towards McMurdo Sound where it could block the access of ships carrying fuel to New Zealand, United States and Italian scientific bases.
“If it continues on its present course it may well almost close off the top of McMurdo Sound,” he said.
This would require an ice breaker, which is used every summer to cut a channel for the fuel supply vessel, to plough through more frozen sea than usual.