The Adélie penguin is one of the best-studied birds in the world and is the subject of research programs from a dozen nations interested in monitoring changes in the environment and the food webs of the Southern Ocean. This species' population has been changing dramatically over the past few decades coincident with a general warming of the maritime portion of Antarctica. When the sea-ice is seen to decline so does the population of Adélie penguins. Further south, however, the population is increasing.