Thousands of Emperor Penguin Chicks Feared Drowned in Sea

Every April, emperor penguins return from the sea and march tens of miles inland to breeding sites on various patches of the ice to lay a pair's single egg for the year. As the Antarctic winter begins, the females head back out to sea to feed while the males incubate the eggs through the brutal, months-long night of the winter, a process made famous by the film March of the Penguins.

After the winter passes, the females return and the males pass the eggs off to them before going out to sea to feed, having lost nearly 40 percent of their body weight during the winter. By August, the first chicks start to hatch and the colony spends the next five months on the sea ice raising their young.

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Every summer, beginning in December, the warmer weather and 24-hour sunlight breaks apart the sea ice these penguins live on. By then the chicks have grown the adult plumage that enables them to swim, so the entire colony simply swims away. In October or November, on the other hand, it is still springtime and though colder than summer, the weather is particularly stormy.

If the yearly sea ice the colony lived on was weaker than normal, the severe weather in the spring could break it up early, when the emperor penguin chicks were still too young to have molted their fluffy, adolescent down. Scientists suspect that this is exactly what happened in 2016, meaning many, if not most, of the penguin chicks would have fallen into the sea without their adult feathers, causing thousands of them to drown.

Halley Bay Colony Penguins Never Came Back

The sea ice that broke up in 2016 has never properly recovered, according to satellite imagery. As a result, the Halley Bay colony appears to have abandoned the site altogether in search of other breeding grounds.

"The sea-ice that's formed since 2016 hasn't been as strong,” said Dr Peter Fretwell, who was the first to spot the disappearance of the Halley Bay colony along with his colleague at the British Antarctic Survey (BAS), Dr Phil Trathan. “Storm events that occur in October and November will now blow it out early. So there's been some sort of regime change. Sea-ice that was previously stable and reliable is now just untenable."

The researchers at BAS believe the adults may have moved on to other breeding sites, avoided breeding altogether since 2016, or were absorbed into other colonies. A colony of emperor penguins about 30 miles away near the Dawson-Lambton Glacier has seen a large increase in population since 2016, for instance, possibly from an influx of Halley Bay penguins.

It is impossible to know the exact fate of the emperor penguins of the Halley Bay colony, but even if they do return to the Halley Bay site in the future, the entire Brunt Ice Shelf that it sits on the edge of is set to calve off and fall into the sea and become an icebreg the size of London, meaning that any attempts to re-establish the colony would be doomed from the start.