Aerial Survey of Harmony Point and The Toe (ASPA 133, Nelson Island , Antarctica) for Pygoscelis penguins and Antarctic Shag counts.

This data set contains high resolution ortho-rectified mosaics constructed from drone aerial images, and shapefiles of seabird nests positions. Aerial imagery was collected using a DJI Mavic 3 unmanned aerial vehicle (UAV) equipped with a high-resolution camera at Harmony Point (Fig 1a,b,c). A total of 14 flights were conducted during the peak of the penguin incubation period in December 2024, at an altitude of 100 m above ground level and a speed of 5 m/s, ensuring uniform image resolution while minimizing disturbance to breeding birds. Flights were conducted only under favorable weather conditions. Multiple images were captured with 50% to 70% overlap, totalling 5,932 images. The collected drone imagery was processed using Agisoft Metashape Professional software to generate high-resolution orthomosaic images. Flight operations adhered to guidelines established by the Scientific Committee on Antarctic Research (SCAR) and complied with all permit requirements for drone use in ASPAs. Nest counts were conducted manually by placing a point on each identified nest structure within the orthomosaic images. The positions of Gentoo penguin breeding groups at Harmony Point were marked on-site using a handheld GPS (Garmin Montana I7) to aid in species identification within the orthomosaic images. We did not have access to the Toe site, so the drone was launched from Harmony Point (∼ 3km). Although it is possible to distinguish between the two penguin species based on nest density, additional imagery was captured at an 80 m altitude to confirm species identification. For Antarctic shags, a nest was defined as a bird and its corresponding anatomical structure. For penguin species, a nest was considered occupied if a bird was observed in an incubation posture within the boundary of a guano stain. Data collection was funded by Instituto Antártico Chileno Programa Áreas Marinas Protegidas (AMP 24 09 052) and ANID, through Instituto Milénio de Biodiversidad de Ecosistemas Antárticos y Subantarticos (Programa Iniciativa Milénio ICN2021_002).