Giant iceberg drastically reduces emperor penguin chick survival rate near Coulman Island

A single, massive iceberg has caused a dramatic 69% decline in emperor penguin chicks at a major Antarctic colony. Researchers from the Korean Polar Research Institute (Kopri) observed this severe drop during the 2025 breeding season at the Coulman Island colony. They counted only 6,658 live chicks in November and December 2025, a significant decrease from the historical average of around 21,000 chicks per season. This marks the lowest number recorded since censuses began in 1983. The study, published in "Communications Earth & Environment," suggests the decline was not due to typical factors like low sea ice, which was normal that year. Instead, a colossal iceberg, approximately 13.9 km long and 4 km wide, became lodged near the colony. This iceberg, which calved from the Nansen Ice Shelf in March 2025, blocked the adult penguins' primary route to the sea for foraging. The iceberg presented a sheer ice wall over 20 meters high on the colony side, with only a narrow, difficult-to-find passage on the eastern flank. Consequently, the penguins' journey to feeding grounds, normally about 9.3 km, extended to roughly 14.9 km, likely longer in practice due to the detour. This increased travel time is believed to have led to starvation among vulnerable newborn chicks, who rely on frequent parental visits for food. Scientists found numerous deceased chicks within the colony, indicating high early-stage mortality. While the study acknowledges its observational nature and does not definitively establish causality, it proposes this iceberg blockage as a plausible explanation for the observed chick mortality. Similar incidents have occurred at other Antarctic colonies, but the Coulman Island iceberg began moving again in January 2026, suggesting the impact may be temporary.