The Royal penguins' breeding season extends from September to March and starts with the male birds coming ashore on Macquarie Island to build their nests, which are lined with grass and stones (5). The females arrive a couple of weeks later and courtship takes place. Males swing their heads up and down and call to encourage the females to become receptive to mating (5). Eventually, two eggs are laid at the end of October, the second egg being the only one that is usually incubated (5). Royal penguins are monogamous and often form large colonies of up to 500,000 birds (5), together with the closely related rockhopper penguins. The nests are usually placed a few hundred metres from the sea and the birds make access routes through the tussock grass (4). Incubation lasts from 30-40 days (5), after which the male guards the chick for up to three weeks while the female provides food (4) (5). After this period, the demands of the chick make it necessary for both parents to collect food, and the chicks usually gather together in small crèches (4). Royal penguins feed largely on krill, small shrimp-like crustaceans, the rest of their diet comprising fish and squid. The parent birds regurgitate partially-digested food from their stomachs to feed their growing youngster (2). When it reaches some 70 days old, the chick will have fledged and can begin to fend for itself. It becomes sexually mature at one year (5).