How does a chicken know if an egg is fertilized?

Answered by Robert Flynn

A chicken’s ability to know if an egg is fertilized or not is quite limited. Chickens do not possess the biological capability to determine the fertilization status of their eggs. Unlike mammals, where fertilization occurs internally, chickens reproduce by a process called external fertilization.

When a rooster mates with a hen, the rooster deposits sperm into the hen’s oviduct. The sperm then travels up the oviduct and can potentially fertilize the egg if one is present. However, the hen does not have any means to detect whether fertilization has occurred or not.

Once the egg is laid, the hen’s role is essentially complete. She will typically lay her egg and move on to other activities, such as foraging or socializing with other members of the flock. Commercial hybrid hens, in particular, have been selectively bred for high egg production and often exhibit minimal interest in their eggs beyond laying them.

It’s worth noting that not all eggs laid by a hen will be fertilized, even if there is a rooster present in the flock. Roosters can be infertile or may not successfully mate with every hen. Additionally, hens have a limited window of fertility during which they are receptive to mating, so not all eggs laid during this time will necessarily be fertilized.

To determine if an egg is fertilized, one would typically need to examine it under a process called candling. Candling involves shining a bright light through the egg to observe its internal contents. Fertilized eggs will show signs of development, such as the presence of veins and a dark spot called the embryo. However, this is a method typically used by humans, and hens do not have the ability to perform such inspections.

A chicken, including a hen, does not possess the ability to know if an egg is fertilized or not. It is a biological process that occurs internally and is not within the awareness or control of the chicken.