Fourteen drone flights over a rocky finger of Antarctic coastline have delivered one of the starkest population counts yet recorded for chinstrap penguins. At Harmony Point, on Nelson Island in the South Shetland Islands, researchers counted 38,080 chinstrap nests in December 2024. The last comparable count, taken by hand in the mid-1990s, put the colony at nearly 90,000 breeding pairs. The new survey, published in the journal Polar Biology, puts the decline at 57 per cent over roughly three decades.
The work was led by Eduardo J. Pizarro of the Pontificia Universidad Católica de Chile and Lucas Krüger of the Instituto Antártico Chileno, with collaborators from the Federal University of Rio Grande do Sul and Chile’s ANID Millennium Science Initiative. Harmony Point sits inside Antarctic Specially Protected Area 133, a status meant to shield its wildlife from disturbance, which made it an obvious candidate for a fresh, systematic count after nearly thirty years without one.
Counting penguins from the air
Hand counts of penguin colonies are slow, and on a site as sprawling and uneven as Harmony Point, easy to get wrong. Researchers walking the ground can miss nests tucked behind boulders or double-count birds that shuffle between sections while the survey is underway. Drones solve much of that problem by capturing the entire colony from above in a single, repeatable pass.
The team flew a DJI Mavic 3 drone over the site fourteen times in December 2024, timed to coincide with peak incubation, when nearly every breeding pair is anchored to a nest rather than out foraging. Flying at 100 metres above ground level, the drone captured high-resolution imagery that was later stitched into a single map of the colony and used to count individual nests by eye and with photogrammetric software. That altitude and method have become close to standard practice for Antarctic seabird surveys over the past decade, replacing the clicker counts and rough area-based estimates that produced numbers like the 1990s figure now used as a baseline.
That comparison has a real limitation. The historical count of nearly 90,000 pairs was itself an estimate, made with less precise tools than a drone survey affords. Some of the apparent decline could reflect improved counting rather than fewer birds. But a gap this large, more than 50,000 nests, is not plausibly explained by methodology alone, and it lines up with a wider pattern already documented at other chinstrap sites in the region.
A colony shrinking while a neighbour grows
The survey’s other headline finding sat a short distance from the chinstrap colony itself. On a small peninsula south of Harmony Point, an outcrop the researchers nicknamed “the Toe”, the drone imagery revealed a gentoo penguin colony of 4,641 nests that had not previously been documented at all. Combined with an existing, largely stable gentoo population of 3,659 nests at Harmony Point proper, the survey put the total gentoo count for the area at 8,300 nests. The Toe also turned out to hold its own chinstrap colony, 8,153 nests, which appears to have shrunk by roughly 45 per cent since a 1970s estimate — though the researchers caution the uncertainty around that older figure is too wide to put much weight on the exact percentage.
Gentoo penguins are the generalists of the Pygoscelis genus, eating a broader diet than chinstraps, tolerating a wider range of sea ice conditions, and steadily expanding their range southward as Antarctic Peninsula waters warm. Chinstraps depend far more narrowly on the tiny shrimp-like crustacean Antarctic krill, and on the sea ice conditions that support dense krill swarms. In the same waters, gentoo numbers have been climbing while chinstrap numbers fall.
The survey also found a smaller, easily overlooked change. Nests of the Antarctic shag, a diving seabird that nests in small colonies alongside penguins, reached 127 at Harmony Point, an 84 per cent increase on the last count in 2018/19 and the highest number on record. The researchers note it still falls within the range of fluctuation the colony has shown since the 1980s, though — a weaker signal than the penguin trends, not a clear confirmation of them.
What is driving the chinstrap losses
The researchers stop short of blaming any single cause. Their paper points instead to a combination of pressures acting together: the effects of a warming climate on chick survival, shifts in where krill can be found as sea ice patterns change, increased commercial krill fishing in some of the same waters, and growing competition from whale populations that were hunted to near-extinction last century and are now recovering and eating krill again.
Chinstrap penguins depend on sea ice in a specific and somewhat counterintuitive way. Unlike emperor penguins, which need stable ice to raise chicks, chinstraps benefit from ice at the margins of their range because it supports the krill blooms their chicks are raised on. Where sea ice has retreated and become less predictable around the South Shetland Islands, krill availability during the critical chick-rearing weeks has become less reliable too, and chick survival has suffered as a result.
These pressures aren’t unique to Harmony Point. Comparable declines have been reported previously at Deception Island, also in the South Shetlands, and at colonies on Elephant Island further to the north-east, where a 2020 survey led by Stony Brook University found some sub-colonies had shrunk by more than three-quarters since the 1970s. Harmony Point adds a well-documented, single-site data point to that regional pattern, gathered with a more precise method than most of the historical counts it is being compared against.
Why a single count matters
A protected area doesn’t guarantee stable wildlife. Harmony Point has carried special protection status for years, and its chinstrap population has fallen by more than half regardless. Protection limits direct human disturbance, such as uncontrolled tourist landings or research trampling. It has no effect on ocean warming or on fishing quotas set far beyond Antarctic waters.
That is precisely why the authors frame their count as baseline data rather than a final verdict. A single survey, however precise, is a snapshot. Its value comes from being repeated: the next drone flight over Harmony Point, in five years or ten, will be measured against 38,080 nests rather than a three-decade-old estimate, and any further slide will be much harder to dismiss as a counting artefact.
For now, the number that matters is simple enough to state plainly. In a colony inside a supposedly protected patch of Antarctic coastline, roughly one in every two chinstrap nests counted in the 1990s is no longer there.