Illustration from “Bird’s Eggs” by Michael Walters
In an earlier blog post I discussed the size, shape, color and weight of a bald eagle egg. But, just what is inside? All birds lay eggs and are known as oviparous which means producing eggs that hatch after exclusion from the body. An obvious advantage is that the female bird does not have to fly around with the weight of the developing young inside her. Eggs begin as three parts, the shell which we can see, and yolk and albumen (egg white), which we cannot see. The yolk contains the fertilized egg cell from which the embryo forms, and is rich in proteins and fat that are the food required by the developing embryo. The albumen is the source of amino acids and minerals and surrounds the yolk. The egg shell not only protects the developing embryo, but is porous and allows the passage of water vapor, ozygen and carbon dioxide, thus permitting the eagle chick to breathe. The eagle eggs in the Norfolk Botanical Garden nest are by now well formed and parts of the birds body could be identified. In a week or so I will describe “getting out of that shell”.