Posted by Ed Maser on April 3, 2007

Q: I have a female mallard duck with a nest and 10 eggs in my flowerbed. Does the male fertilize the eggs after they are layed or is that done when they mate?

State: Pennsylvania

A: Ed, After mating, inside the female, sperm swim up a tube called the oviduct, at the end of which there is an ovum, inside which resides the female sex germ. If the ovum is mature, it's already equipped with yolk, the yellow part of the future egg. The sperm may now fertilize the ovum by penetrating it and uniting the two sex-cells' genetic material.

After fertilization, the ovum with its yolk begins its own journey down the oviduct, a process lasting about 24 hours. During the first three or four hours, moving at about one tenth of an inch (2.3 mm) per minute, albumen (egg white) is added around the ovum and its yolk. The yellow yolk will serve as food material for the developing chick; the white will mainly keep the yolk from drying out, and will give the yolk physical support

Now the future egg slows to about 40 percent of its earlier speed, and membranes are added around the yolk and egg white. Finally the shell is put in place, taking 19 to 20 hours. Then, the hen Mallard lays her fertilized egg! Jim Berry

Jim Berry ( April 9, 2007)