Thousands of emperor penguin chicks drowned when the sea-ice on which they were raised was destroyed in bad weather
The catastrophe occurred in 2016 in Antarctica's Weddell Sea. the colony at the edge of the Brunt Ice Shelf has collapsed with adult birds showing no sign of trying to re-establish the population.
And it would probably be worthless for them to try as a giant iceberg is about to break the site.
The evolutionary chasm of the Brunt Ice Shelf may have done the colonies anyway
The dramatic loss of the young emperor birds is reported by a team from the British Antarctic Survey (BAS)
Drs Peter Fretwell and Phil Trathan noticed the disappearance of the so-called Halley Bay colonies in satellite pictures.
It is possible even from 800km to spot the animals' excrement, or guano, on the white ice and then to estimate the likely size of any gathering
But the Brunt population, which had sustained an average of 14,000
Image copyright DigitalGlobe, and Maxar company
2015: The guano stains at Halley colonies are visible from space
Emperors are the tallest and heaviest of the penguin species and need reliable patches of sea-ice on which to breed, and this ice platform must persist from April, when the birds arrive, until December, when their chicks fledge. ] If the sea-ice breaks up too early, the young birds will not have the right feathers to start swimming
This is what happened in 2016.
Strong winds, which have been dulled out of the sea-ice that has stuck hard to the side of the thicker Brunt shelf in its creeks, and never properly reformed. Not in 2017, nor in 2018.
Dr Fretwell told BBC News: "The sea-ice that has been formed since 2016 has not been as strong as Storm events that occur in October and November will now blow it out early. "
The BAS team believes that many adults have either avoided breeding in these later years or moved to new breeding sites across the Weddell Sea. A colony some 50km away, near the Dawson-Lambton Glacier, has seen a big increase in its numbers