Adults arrive at the nest sites to breed in September, and after a period of burrow excavation and repair, begin egg laying around mid October. Two equally sized eggs are laid 4 days apart, each with a weight of around 125g. Incubation takes around 40 days, with the female incubating the eggs for the first shift, while the male feeds at sea. He forages at distances of up to 500km away from the breeding site, before returning to relieve the female some 15 or 20 days later. She then goes to sea for a similar period, and when she returns, the two birds change over at regular intervals until the eggs hatch.
Both parents continue to brood the chicks in turn on a daily basis, for a period of about 30 days. Chicks are fed daily, with adults leaving the colony in early morning, and returning with food later the same day. Magellanic penguins mostly forage within 30km of the nest site during chick-rearing, except in the Falklands where longer foraging trips are forced by conflict with commercial fishing.By the end of 30 days the chicks have developed their mesoptile plumage, and are able to venture out of the burrows. At this stage they look very different from the adults, being a browny grey above, and creamy white below. Living in burrows, chicks have good protection from both predators and cold weather while both parents are away feeding, and consequently they do not form creches in the way that most surface-breeding species do. Whilst burrows offer good protection from most weather conditions, heavy rain can result in flooding of the burrows in certain areas. Chicks rarely drown in such circumstances, but often become wet and cold. Mesoptile plumage provides excellent insulation when dry, but it lacks the waterproofing qualities of the adult plumage and loses much of its insulation properties when wet. Consequently many chicks can die from hypothermia in such conditions. Living in burrows also means that both chicks and adults become infested with penguin fleas.
