Update on the abundance and distribution of Macaroni Penguins (Eudyptes chrysolophus) in the Antarctic Peninsula region

Several studies have examined the potential impacts of climate change on the abundance and distribution of Antarctic penguin species, particularly in the genus Pygoscelis. However, less attention has been given to traditionally sub-Antarctic penguin species. The Macaroni Penguin (Eudyptes chrysolophus) is one such sub-Antarctic species whose presence in Antarctica has historically been restricted to colonies on the South Shetland Islands and adjacent islands, but their status in the region has not been updated in decades. We compiled census data on all known Macaroni Penguin breeding colonies in the Antarctic Peninsula region in order to estimate the total Antarctic population. We estimate a population of 8053 breeding pairs for the region, which represents an approximately 10.7% increase since the last regional census in 1993. We identify local population changes at different colonies in comparison to historical census data. We also identify vagrant sightings in the region, as they may reflect prospecting of new breeding habitat, especially as ice-free areas continue to expand due to climate change. Our assessment identifies the South Shetland Islands and South Orkney Islands as notable data gaps.