Landsat's guano record backdates 18 emperor penguin colonies by 17 years on average

The U.S. Fish and Wildlife Service listed emperor penguins as threatened in 2022, and the International Union for Conservation of Nature classified them as endangered in 2026.

After Antarctic sea ice cover hit a record low in 2022, British Antarctic Survey researchers reported "catastrophic" breeding failures among Bellingshausen Sea colonies.

Two studies published in 2026 used decades of Landsat observations to fill gaps in understanding of emperor penguin colonies; they appeared in Remote Sensing in Ecology and Conservation and Antarctic Science.

Landsat cannot resolve individual penguins; researchers identify colonies from the guano stains that accumulate where thousands of birds congregate on the ice.

Landsat has imaged Antarctica continuously since the early 1980s, providing one of the few systematic long-term records of remote penguin colonies.

Researchers at the University of Freiburg found that 18 colonies predate their initial identification by an average of 17 years.

The roughly 6,000-bird Smyley Island colony in the Bellingshausen Sea dates to at least 1989, two decades earlier than previously known.

Other colonies that predated their earliest known presence by 20 or more years included those at Barrier Bay, Brownson, Luitpold Coast, Ragnhild, Smith and Verdi Inlet.

Smyley Island is among the colonies that may have suffered a total breeding failure in 2022, and satellite images that year show the colony splitting up, with some penguins moving onto a large iceberg grounded near the coast.

Despite persistently low sea-ice conditions since 2022, the Smyley Island colony has continued to appear in satellite imagery, generally establishing itself near icebergs along the edge of the ice shelf, with December 2025 the most recent month Landsat observed it.

Michelle LaRue said "We're seeing a degree of resilience in the Smyley Island colony" and "They seem to be doing OK now, and we will continue to monitor them to learn more about their behavior."

LaRue said one bad breeding year, even a total failure, does not mean the end of a colony, and that blizzards and predators can also cause years with very low chick survival.

LaRue said "It's when we start to see frequent breeding failures year after year that the birds won't be able to keep up, and it starts to be a problem for a colony."

LaRue said "There's little baseline information for what's 'normal' for most of these colonies," which has made projecting future population levels a challenge.

Except for a few well-studied colonies, scientists have known little about how long many emperor penguin colonies have existed, how their populations have changed, or how they responded to past disruptions in landfast sea ice.

The phys.org report states that some models project the species could disappear by 2100 but does not describe what those models assume about breeding-site fidelity.

The phys.org report introduces a second 2026 study under the heading that breeding sites are more flexible, but the text available does not give that study's figures.

Eighteen colonies backdated by an average of 17 years amounts to about 306 colony-years of occupancy that predates the written record.

Smyley Island's satellite-documented occupancy now spans about 36 years, from at least 1989 to December 2025.

Smyley Island's previously known earliest presence dated to roughly 2009, since the new date of at least 1989 is described as two decades earlier.

Some models project that emperor penguins could disappear by 2100 as their habitats become inhospitable.

The 18 backdated colonies equal about 27% of the 66 colonies currently known from satellite surveys, though the Freiburg study's own sample size is not stated.