Ice siege puts penguins in peril

By ANNE BESTON

Thousands of Antarctic penguins are dying of starvation and exhaustion as giant icebergs and unprecedented levels of ice in the Ross Sea cut them off from breeding grounds.

One of the largest colonies of Adelie penguins in the world - at Cape Crozier, home to 130,000 breeding pairs - is now almost surrounded by impassable ice.

A small colony of 1200 Emperor penguins at Cape Crozier, discovered by members of explorer Robert Scott's expedition in 1911, has bred no chicks, abandoning efforts to breed as starvation closed in.

An Adelie penguin colony at Cape Royds is expected to die out.

In the Ross Sea region, site of New Zealand's Scott Base and America's McMurdo Station, scientists believe the mortality rate of the Adelie penguin could be as high as 20 to 30 per cent in some rookeries.

The existence of others is in jeopardy as the breeding season peaks over the next two months.

Antarctica New Zealand's head of science, Dr Dean Peterson, said penguins were dying from exhaustion, their chicks starving as they lost their struggle to trek between their nests and their food source.

"They are having to backpack over an extra 20 to 30km and they're running out of food and energy."

American penguin researcher Dr David Ainley, based at McMurdo, believes the small colony at Cape Royds will "fail totally".

Dr Peterson said up to 70km of extra sea ice surrounded the small Adelie colony at Cape Royds, an almost impossible distance for a bird whose average walking speed is roughly 1 km/h to 2 km/h.

Access to the ocean is vital. Penguins come ashore to breed and then take it in turns to leave the nest to feed on krill, fish and squid before returning to regurgitate the food for their chicks.

Dr Ainley said breeding at Cape Royds had increased in recent years because sea ice had been decreasing. His research had also found that a small colony of Emperor penguins at Cape Crozier, on the eastern side of Ross Island, raised no chicks this season.

Dr Peterson said some of the Emperor penguins moved to another rookery at nearby Beaufort Island, but the different conditions caused many failed hatchings.

Cape Bird, on the northernmost tip of Ross Island, normally had about 150,000 birds but numbers were down.

Two giant icebergs are causing the problems. One is 37km wide and 87km long and the other 18.5km wide and 55km long.

They broke from the Ross Ice Shelf in March 2000 and have gradually migrated to the northeast of McMurdo Sound.

Dr Peterson said the icebergs formed a barrier between the Ross Sea region and the open sea, so waves had less chance to break up the ice. A lack of storms last winter also contributed.

It was not the first time penguin colonies had experienced bad breeding seasons and scientists would try to discover what effects this season had had on populations.

He said they could do that by tracking dozens of birds that had been tagged by researchers over the past few years.

CLASS ACT

* Adelie penguins are classics of their kind, with a "tuxedo" white front and waddling gait. They often appear in TV commercials.

* The Antarctic population is estimated at between 3.5 million and 4 million breeding pairs.

* They are the most widely distributed penguins in the Antarctic.

* Adults weigh only about 5.5 kg and stand but 71cm high.

* They come ashore to breed in October and chicks are raised between December and March by both parents.

* They start breeding at between 3 and 5 years of age and live up to 20 years.