Everyone knows that hens lay eggs and if they’re fertilized they’ll produce a chick and if they’re not they’ll end up in a plate. But how do chickens reproduce? Can hens have twins? How long do hens lay fertilized eggs? Let’s find out.
Compared to mammals, chicken reproduction is quite unique. When a rooster is ready to fertilize a hen he’ll engage in a “foreplay dance” moving and clucking around the hen to signal his intentions. As he mounts her, the transfer of sperm happens quite quickly without any penetration. Fertilization is achieved when a rooster and a hen’s cloacas touch, allowing sperm transfer in what’s called a “cloacal kiss”.
The cloaca is an amazing organ. It’s a chicken’s rear orifice with three purposes (in a hen): dispose of feces, lay eggs and receive sperm. However when a chicken lays an egg it doesn’t get covered with feces on their way out. This is because when a chicken lays an egg, her uterus gets inverted beyond the cloaca to avoid the egg touching any feces. Curiously enough the cloaca allows chickens to be artificially inseminated in commercial chickens, where the rooster’s cloaca gets massaged to collect the semen, which is diluted and transferred into a hen’s cloaca.
Once a hen is inseminated, she’ll store the semen in the oviduct for up to 30 days meaning after one insemination, eggs may be fertilized for up to four weeks.
The hen first will produce the yolk in her ovaries. Once it’s formed it’s released to the oviduct where it can be fertilized. As it keeps traveling along the oviduct, the egg white and shell will form around the yolk. A hen takes roughly about 26 hours to produce an egg. Out of those 26 hours, 20 are required to make the shell. Once the egg finishes traveling along the oviduct the hen will lay it. However that doesn’t mean the hen will want to incubate them.
For a hen to incubate an egg, she’ll have to be in the right mood. We traditionally call chickens in this mood as “broody”, which means that the chicken is willing to lay on eggs, turn them and take care of them. A chicken can get broody regardless of wether they have had any contact with a rooster. Some chickens, like the Cochins and the Silkies make great mothers that will take care of eggs relentlessly and may even accept eggs from other mothers. If your chickens doesn’t get broody you can purchase an incubator and take care of the eggs yourself.
Finally, after 21 days, a chick comes out of the egg.
Some chickens however may lay eggs with double yolks. This occurs very early in the process, when a chicken releases two yolks from the ovary at the same time. A British company is actually selling “double yolkers” due to their popularity. So what happens if both of those yolks get fertilized?
For chicks to get out of the egg, they’ll have to peck at the air space on top of the egg. However in an egg with two chicks, there’s just not enough space for both of them to do it so they’ll peck to each other. In this case usually neither of them will make them. However if you keep an eye on them by “candling” the eggs you can rescue them by carefully helping them to open the egg.
What did you think? Did any of this surprise you? Let us know in your comments below!