All but two Adelie penguin chicks have starved to death in their east Antarctic colony, in a breeding season described as "catastrophic" by experts.
Unusually high amounts of ice late in the season meant adults had to travel further for food.
It is the second bad season in five years after no chicks survived in 2015.
Conservation groups are calling for urgent action on a new marine protection area in the east Antarctic to protect the colony of about 36,000.
WWF says a ban on krill fishing in the area would eliminate their competition and help to secure the survival of Antarctic species, including the Adelie penguins. The conservation organisation has been supporting research with French scientists in the region monitoring penguin numbers since 2010.
The protection proposal will be discussed at a meeting on Monday of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).
Adelie penguins, the most southerly breeding bird in the world, are found along the Antarctic coast.
They breed from October to February, typically laying two eggs in nests made of stones, and parents take turns to incubate the eggs.
Breeding adults may have to travel up to 50-120km to catch food which they take back and regurgitate for their chicks