Eiders are the largest ducks found in the northern hemisphere. The male’s plumage is black, white and green, while the females are russet-brown to grey. Broods of females often come together to form ‘creches’ of a few to over 150 ducklings with non-breeding females accompanying them for protection. Eider down comes only from the belly feathers of the female eider duck, which she will shed naturally due to hormonal changes during the egg-laying period. The feathers will line the nest to insulate the eggs, while the bare spot on her belly will allow her to emit heat directly to the eggs. Iceland is the world’s biggest harvester of eiderdown and the feathers are replaced with hay, causing no harm to the birds or their eggs.