Fact of life

Emperor penguins breed almost exclusively on sea ice and so are perhaps the only species of bird that never sets foot on land.

They begin their breeding cycle when other Antarctic penguins have finished theirs, at the end of April to May. Other smaller penguins at this time head north away from the encroaching winter while the Emperors head south into it. They seem to choose very dramatic sites, a large flat area where they can waddle when carrying their egg or chick on their feet surrounded by high ice cliffs or icebergs that help to give a little shelter from the winds.

Eggs are laid in May and June, they are the smallest egg relative to body size of any bird, being around 0.4kg (1.1lb) just under 1.5% of the mass of an adult bird.

At this point, the males take charge of the egg. No nest is built and the egg is incubated on the feet of the parents, a special fold of abdominal skin covers the egg to keep it warm. The mother penguins then set off back to sea and do not return for nearly four months.

The male Emperors with their valuable eggs sit huddled together on the ice throughout the dark weeks and months of the Antarctic night. The average temperature is around -20°C (-4°F) going down to -50°C (- 58°F) and with winds that gust up to 200km per hour (124mph). The males do not eat at all throughout this time, but just sit and wait and protect their egg, (later the chick) until their mate comes back to relieve them.

Very few people have seen an emperor penguin huddle in the winter in a savage place where ice and cold are king and the penguins spend their days in silence. The only events are changing position in the huddle (see below) and the immense spectacle of the ghostly red, violet and green of the southern lights or Aurora Australis playing in the dark skies above their heads.

 

An Emperor Penguin Swims Underwater 

Males can be sat incubating and waiting for over 120 days (average 115), during this time they will lose about 40% of their body weight.  They use less energy when asleep which they do so as long as possible, it is not unusual for emperor penguins to sleep for 20 or more hours a day under these conditions - even up to 24 hours a day, to conserve their food supplies and increase their and their chick's chances of survival.

Emperor Penguin Family, Weddell Sea, Antarctica

They survive by huddling together for warmth, very unusual behaviour for adults of other penguin species which are usually aggressively territorial. They also take it in turns to occupy the coldest most exposed outside positions. Without this huddling behaviour, they would unable to endure the combined conditions of fasting, bitter cold and hurricane force winds and would not be able to live and breed in the way they do. Even though they are close together during these huddles, they have been recently shown to be not quite touching. if they touched and squashed the puffed out feathers down it would reduce the insulating value and make them colder, so they really fine-tune the process.

It's not all altruistic behaviour though, and taking it in turns. The ones that have been on the outside on the windward side wander off to the leeward side when they've had enough so exposing the next "layer" of penguins. The whole huddle can wander over quite an area in this way in very cold and/or windy conditions.