Continental-scale mapping of Adélie penguin colonies from Landsat imagery

Breeding distribution of the Adélie penguin, Pygoscelis adeliae, was surveyed with Landsat-7 Enhanced Thematic Mapper Plus (ETM+) data in an area covering approximately 330° of longitude along the coastline of Antarctica. An algorithm was designed to minimize radiometric noise and to retrieve Adélie penguin colony location and spatial extent from the ETM+ data. In all, 9143 individual pixels were classified as belonging to an Adélie penguin colony class out of the entire dataset of 195 ETM+ scenes, where the dimension of each pixel is 30 m by 30 m, and each scene is approximately 180 km by 180 km. Pixel clustering identified a total of 187 individual Adélie penguin colonies, ranging in size from a single pixel (900 m2) to a maximum of 875 pixels (0.788 km2). Colony retrievals have a very low error of commission, on the order of 1% or less, and the error of omission was estimated to be ~ 3 to 4% by population based on comparisons with direct observations from surveys across east Antarctica. Thus, the Landsat retrievals successfully located Adélie penguin colonies that accounted for ~ 96 to 97% of the regional population used as ground truth. Geographic coordinates and the spatial extent of each colony retrieved from the Landsat data are available publically. Regional analysis found several areas where the Landsat retrievals suggest populations that are significantly larger than published estimates. Six Adélie penguin colonies were found that are believed to be previously unreported in the literature.