Breeding cycle
Birds arrive at their colony, usually an ice and snow-free headland, spit or island around the Antarctic coastline. Males usually arrive first during mid- to late-October to claim nest sites and begin nest construction.
Nest building
The nest consists of a simple platform of small stones and rock chips. These are frequently added-to during incubation, and are often stolen from neighbouring nests. Stones allow good water drainage; cold and wet eggs or chicks quickly die.
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| Adélies mating |
Pair formation
Pair bonding is accompanied by loud mutual displays. After copulation (the male bird stands on the female's back and transfers sperm to her cloacca), the eggs are fertilised and laid a few days later.
Egg laying
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| Adélie incubating an egg |
Egg laying takes place in late November to early December. Normally a single clutch of two eggs is laid over 2 to 3 days. A third egg may be laid if the first is lost. Eggs are white, about 72 mm long, 55 mm wide and weigh about 120 g; similar to a large hen's egg.
Incubation and guarding
Usually the male (85% of the time) incubates for the first 2 weeks while the female is at sea. He will have fasted for nearly a month at this stage! Turns on the nest alternate after the female returns, with shorter and more frequent spells at sea. Up to 70% of eggs laid will hatch over a 4-week period around late December. The second egg hatches about one day after the first. Chicks have a large yolk sac within the body cavity so they can last for a few days while waiting for the parent at sea to return with their first meal.
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| Penguin guarding a 15-day-old chick |
Once the eggs hatch (after about 34 days), the parents guard the chicks at the nest site until they are old enough to crèche. Chicks are covered with grey down with dark, sooty, blackish heads. The down is not waterproof but provides good insulation for the chicks on land. Chicks develop thicker, 'woolly', dark-grey down after 10 days. During the guard stage the parents change duty every 1 to 2 days. Foraging trips are up to 110 km from the colony. Chick meal sizes are up to 300 g.
Crèching
Chicks gather together in large groups for protection and warmth as both parents are now busy collecting food for their rapidly growing chicks. Individual chicks chase their parents when they return from sea, noisily begging for food, which the parents regurgitate. Meal size is now up to 650 g. This period lasts for the next 25 to 35 days.
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| Penguin chick moulting |
Chick moulting
As the chicks develop they loose their soft down, which is replaced with waterproof feathers. After 50 days the birds are nearly fully feathered.
Fledging
At the end of January the adults stop feeding their chicks. From this point on the chicks have to fend for themselves, learning to swim and catching their own food. Chicks have short swims for a day or two before leaving the colony in early to mid-February.
Adult moulting
After the chicks fledge, the adults need to regain condition so they can cope with moulting. Most adults and juveniles moult over a period of 2 to 3 weeks in the pack ice. They don't feed at this time. Adélies winter in the outer edge of the pack ice near the Antarctic Convergence.