Multi-modal survey of Adelie penguin mega-colonies reveals the Danger Islands as a seabird hotspot

Despite concerted international effort to track and interpret shifts in the abundance and distribution of Adelie penguins, large populations continue to be identified. Here we report on a major hotspot of Adelie penguin abundance identified in the Danger Islands off the northern tip of the Antarctic Peninsula (AP). We present the first complete census of Pygoscelis spp. penguins in the Danger Islands, estimated from a multi-modal survey consisting of direct ground counts and computer-automated counts of unmanned aerial vehicle (UAV) imagery. Our survey reveals that the Danger Islands host 751,527 pairs of Adelie penguins, more than the rest of AP region combined, and include the third and fourth largest Adelie penguin colonies in the world. Our results validate the use of Landsat medium-resolution satellite imagery for the detection of new or unknown penguin colonies and highlight the utility of combining satellite imagery with ground and UAV surveys. The Danger Islands appear to have avoided recent declines documented on the Western AP and, because they are large and likely to remain an important hotspot for avian abundance under projected climate change, deserve special consideration in the negotiation and design of Marine Protected Areas in the region.