How do Penguins Stay Warm?

How do Penguins Stay Warm?

Emperor penguins breeds in the coldest environment of any bird species, where temperature reach as low as -40 C.
 
The first line of deffense that keep penguins warm is their plumage which provides from 80-90% insulation.
 
Below the feathers there are a subdermal fat layer with thick up to 3 cm.
 
Finally penguins have a sophisticated internal mechanism which is able to thermoregulate its body temperature.