Drone Survey Reveals a Severe Chinstrap Penguin Decline and a Novel Gentoo Colony in an Antarctic Specially Protected Area

Seabird populations in Antarctica are sensitive indicators of environmental change. Understanding their population dynamics is crucial for assessing the health and future of the Antarctic ecosystem. This study provides an updated population assessment for three key seabird species - the Antarctic Shag (Leucocarbo bransfieldensis), Gentoo Penguin (Pygoscelis papua), and Chinstrap Penguin (P. antarcticus) - in the Antarctic Specially Protected Area (ASPA) 133 on Nelson Island. Using drone-based imagery and photogrammetric analysis, we conducted comprehensive nest counts to evaluate current population status against historical data. Our results reveal a pronounced 57% decline in the Chinstrap Penguin population at Harmony Point since the 1990s, with 38,080 nests counted compared to a historical estimate of nearly 90,000. In contrast, Gentoo Penguin numbers at Harmony Point (3,659 nests) have remained stable after a previously documented increase. We also provide the first population estimate for a large Gentoo Penguin colony at one small peninsula located south of Harmony Point, known as the Toe, with 4,641 nests, and report an 84% increase in Antarctic Shags, with 127 nests recorded at Harmony Point. These findings align with regional species-level trends and provide critical baseline data for monitoring the impacts of rapid environmental change on Antarctic seabird communities.