The Macaroni Penguin is a large, crested penguin, similar in appearance to other members of the genus Eudyptes. An adult bird has an average length of around 70 cm (28 in); the weight varies markedly depending on time of year and sex. Males average from 3.3 kg (7 lb) after incubating, or 3.7 kg (8 lb) post-moult to 6.4 kg (14 lb) pre-moult, while females average 3.2 kg (7 lb) post-moult to 5.7 kg (13 lb) pre-moult. The head, chin, throat and upperparts are black and sharply demarcated against the white underparts. The black plumage has a bluish sheen when new and brownish when old. The most striking feature is the yellow crest that arises from a patch on the centre of the forehead, and extends horizontally backwards to the nape. The flippers are blue-black on the upper surface with a white trailing edge, and mainly white underneath with a black tip and leading edge. The large bulbous bill is orange-brown. The iris is red and there is a patch of pinkish bare skin from the base of the bill to the eye. The legs and feet are pink. The male and female are similar in appearance, although males tend to be slightly larger. Males also bear relatively larger bills, which average around 6.1 cm (2.4 in) compared to 5.4 cm (2.1 in) in females; this feature has been used to tell the sexes apart. Immature birds are distinguished by their smaller size, smaller duller brown bill, dark grey chin and throat, and absent or underdeveloped head plumes, often just a scattering of yellow feathers. The crest is fully developed in birds aged 3–4 years, a year or two before breeding age. Macaroni Penguins moult once a year, a process in which they replace all of their old feathers. They spend around two weeks accumulating fat before moulting because they do not feed during the moult, as they cannot enter the water to forage for food without feathers. The process typically takes three to four weeks, which they spend sitting ashore. Once finished, they go back to sea and return to their colonies to mate in the spring.