Sentinels for a lost world

Some of climate's best canaries are turning out to be penguins. Down the mine, an upturned songbird in a cage was the first warning of a deadly gas seep. Above ground, an age of fossil fuels later, there are different silences.

In the sub-Antarctic, king penguins fledge fewer chicks if the parents must forage in warming seas. Rising waters are swamping limited nesting space for African penguins in Namibia.

But it's on the the west coast of the Antarctic Peninsula that the signal is clearest. The raucous cacophony of Adelie penguins has disappeared from the landscape as colonies collapse.

"There are no sounds but the wash of the sea, the occasional calls of skuas."

"Every penguin is gone, the nests are abandoned. Listen to the silence. The silence of absence. The sound of failure."