III.

Physical Characteristics

Penguins vary in size from the little penguin (Eudyptula minor), which weighs 1.1 kg (2.4 lb) and is about 40 cm (16 in) tall, to the emperor penguin, which grows to 30 kg (66 lb) in weight and stands about 115 cm (45 in) tall. The emperor penguin is small compared to the fossil penguin Anthropornis, which lived 37 million to 45 million years ago on Seymour Island near Antarctica. Fossil records indicate that Anthropornis was around 170 cm (66 in) in height.

All penguins have a black back and head and a white breast, but individual species can be distinguished by certain physical characteristics. For instance, the birds in the genus Eudyptes are commonly known as crested penguins for the tuft of bright yellow plumage on their head. Adélie penguins have white, spectacle-like rings around their eyes. Other penguins can be distinguished by bare, pink skin on the head and neck, or varied black and white breast bands. Penguin bills can be black or red, ranging in shape from short and stout to long and curved. Penguin feet are webbed with three toes. Male and female penguins are similar in appearance, although males usually weigh more than females and there are small differences in bill size between the sexes.

Penguins are well adapted to cold weather. Their short, stiff feathers form a dense waterproof coat that prevents excess heat loss. Some species have a thick layer of blubber under their skin, but this fat layer mainly acts as a food reserve and contributes little to insulation.