The Chinstrap Penguin (Pygoscelis antarcticus) have a circumpolar distribution, centred mostly on Antarctica. Chinstrap penguins weigh between 3-5 kg and stand around 72 cm tall – males are larger and heavier than females. They eat fish, shrimp, krill and squid and often swim up to 80 km offshore to hunt. They nest in rookeries and build shallow nests of small stones to keep their eggs dry and to protect them from freezing. There is stiff competition amongst the birds for suitable stones, and theft of stones from nests is common. Chinstrap Penguin rookeries are very smelly because of the build-up of droppings around the nests and along the trails used by the birds to move to and from the sea to their nests. Their droppings are pink from the carotene pigments in their prey and foul their breast feathers. The adult birds often walk the long distance to the sea to bathe and to feed before walking up hill back to the rookery on 'penguin highways'. Chinstrap Penguins breed during the austral summer, and usually raise two chicks. Both parents share incubation of the eggs and rearing of the chicks. The main predator of Chinstrap Penguin eggs and chicks is the Brown Skua. These birds are members of a breeding colony on Half Moon Island in the South Shetland Islands west of the Antarctic Peninsula, and had to swim through icy water to get back there.