(May 20, 2015, The Auk: Ornithological Advances)—It takes a lot of nutrients to build an egg. One of the big questions among researchers who study the eggs of migratory birds is where those nutrients come from—does the mother make the egg directly out of what she eats during the breeding season, or does she save up nutrients consumed on her wintering grounds? The answer appears to be both for Common Eiders, large, sea-going ducks that breed in the Arctic, according to new research published in The Auk: Ornithological Advances. Keith Hobson of Environment Canada and his colleagues analyzed the carbon and nitrogen isotopes found in the eggs of Common Eiders breeding in the northern Baltic to trace the elements in the eggs to their origins. They found that proteins in the egg yolk, which is produced first, include nutrients that originated at the eiders’ wintering ground off the coast of Denmark. However, the albumen or egg white is made almost entirely from nutrients consumed locally on the breeding grounds. Because Common Eider use nutrients from both ends of their range in their range, they need quality habitat in both the winter and the summer to produce healthy chicks. Read the full article at http://www.aoucospub...42/AUK-14-294.1.
Photo credit: G. Gilchrist