Chinstrap penguins. Group of adult Chinstrap penguins (Pygoscelis antarcticus) on rocks. Chinstrap penguins are easily recognized by the narrow black stripe extending under their heads. They are well known as some of the boldest and most aggressive penguins and often live on large icebergs in open ocean. On land they build circular nests from stones and the chicks hatch after about 35 days. The chicks stay in the nest for 20 to 30 days before they form a group (creche) with other chicks. At around 50 to 60 days old, they moult, gaining their adult plumage, and go to sea. Photographed on the coast of the Antarctic peninsula.