Emperors are the largest of all penguins in size. They are about one meter tall and weigh approximately 30-40 kilograms. They have a black head, a blue-gray neck with a bright orange patch near the ears and pale yellow breast fading into white. Emperors are bigger and chick-rearing takes longer than it does for the smaller Adelies. Chicks need to be independent by summer when food sources are most plentiful, so the eggs have to be laid early. In the southern autumn (April-May) colonies assemble on the sea ice in sheltered bays. A single egg is laid in May or early June and is incubated by the male for two months over the coldest part of the year. The egg is kept on top of the male's feet covered by a flap of blood-rich skin and feathers to keep it warm in temperatures down to -50°C. The male doesn't eat during this time; it would use too much energy to go back and forth across many kilometers of ice to the sea if incubation duty was shared with the females. Instead they have adapted to these extreme conditions by huddling together in huge groups and using their reserves of fat for energy and insulation.