Study Penguin colony hit hard by melting sea ice

Antarctica's Halley Bay usually attracts 14,000 to 25,000 breeding pairs, or up to 9 per cent of the world's entire population of emperor penguins, each year.Photo / AP

The world's second largest colony of emperor penguins has lost almost every chick for three years in a "catastrophic" breeding failure linked to melting sea ice.

Antarctica's Halley Bay usually attracts 14,000 to 25,000 breeding pairs, or up to 9 per cent of the world's entire population of emperor penguins, each year.

But since 2016 almost every chick hatched there has died before reaching fledgling age as ice melts early, a study of satellite images by the British Antarctic Survey has found.

"These images have clearly shown the catastrophic breeding failure at this site over the last three years," said Dr Peter Fretwell, who led the study, which was published yesterday.

Emperor penguins incubate, hatch and raise their young on sea-ice during the Antarctic winter.

For successful breeding, pairs need a stable ice shelf to last from April, when they arrive and lay a single egg, until December, when chicks fledge and the penguins move to the open sea.

In 2016, the ice sheet broke up in October, months before the chicks were ready to leave. There was no breeding there in 2017, and only a little in 2018.

Some of the pairs appear to have relocated; the nearby Dawson Lambton breeding site, which previously hosted just a few thousand penguins, saw 11,117 pairs in 2017 and 14,612 in 2018, the study said.

Dr Phil Trathan, co-author of the study, said it was impossible at this stage to specifically attribute the changes in Halley Bay to climate change, but said the size of the breeding failure there was "unprecedented".

Ice conditions in Halley Bay were stable for at least 60 years and it was previously thought to be shielded from the effects of climate change.