Emperor penguin (Aptenodytes forsteri) scratching its head at a nesting site during the breeding season. The emperor is the largest of the penguins, standing around 115 centimetres tall and weighing 30 to 40 kilograms. It is the only penguin to breed during the Antarctic winter. Each pair produces a single egg, which the males incubate. Males fast during the two-month incubation period and lose almost half their body mass by the end. After the egg hatches in around mid-July, the male and female take it in turns over the following months to shelter the chick and feed it. Photographed in October, in Antarctica.