Chickens fertilize eggs through a process involving mating between a rooster and a hen. Here is how it works:
- The rooster and hen engage in mating behavior where the rooster transfers sperm to the hen via "cloacal contact" or a "cloacal kiss." This means their cloacas (a common opening for reproductive and digestive tracts) touch, allowing sperm to pass from the rooster to the hen
- Once inside the hen, the sperm can be stored in specialized sperm storage glands within her reproductive tract for up to several weeks. This allows the hen to fertilize multiple eggs over time from a single mating
- Fertilization occurs in the hen’s oviduct before the eggshell forms. The sperm meets the ovulated egg (which has not yet developed its protective shell) and fertilizes it
- After fertilization, the egg continues to develop its shell and is laid by the hen about 26 hours later. The first fertilized egg is typically laid 36-48 hours after mating
- Hens can lay eggs without a rooster, but those eggs will not be fertilized. Fertilized eggs are necessary for chick development and hatching
In summary, fertilization happens internally when the rooster deposits sperm into the hen’s cloaca during mating, sperm travels to fertilize the egg inside the hen before the shell forms, and then the fertilized egg is laid
