How Are Birds’ Eggs Fertilized? Everything You Should Know!


Birds are renowned as eggs-laying species However, are you aware of the solution to the question “How do eggs of birds get fertilized?”

Similar to mammals, the process of reproduction for birds starts when the egg (or an ovum) is in contact with sperm and becomes fertilized. After fertilization, the ovum transforms into the egg’s nucleus comprised of the yolk as well as an outer shell to protect it.

Domestic birds, like ducks and chickens, can make eggs that are not fertilized with sperm. They are the eggs you typically buy from stores or in supermarkets.

Common Mating Behaviors and Alternative Reproductive Strategies

four bird's eggs on nest

Because the body structure of the majority of birds is not used as a spermatic tubule, their reproductive habits differ from reptiles and mammals.

The mating process of reptiles and mammals is carried out over a prolonged period of time, the bird’s mating process is brief-lived. While reptiles and mammals require an interval between mating, birds are able to mate multiple times throughout the day..

The majority of birds have lost their internal organs throughout evolution, however, around three percent of males in the living species have penises. Examples include ostriches, swans as well as ducks, and geese. The other birds, including penguins, eagles, or seagulls do not have penises. Chickens may also have penises however they’re all tiny and narrow tubes, so they cannot get into them. If that’s the situation, what do they do?

In this stage, the male’s semen is now the “cloacal kiss”. The mating posture and position of birds can differ depending on the species, but it’s the norm for males to stand on top of females. When this happens they will both be facing the same direction as the female may shift her tail towards the other side to allow the male to effortlessly rub his female’s cloaca.

 Bird Egg Development  

The birds have two ovaries as their embryos. With the exception of Australian brown kiwi as well as some raptors, adult birds generally have only one ovary, the left and the right ovary declining.

The ovum, also known as an egg, is derived from an ovary’s follicle that is developing on the outside of an ovary splits, and is inserted into the end of the fallopian tube (like the fallopian tube of a woman). As these cells enter the fallopian tube the yolk sac that is which is the “nutrient” supply for the embryo’s development is covered by an outer layer.

The ovum inside the yolk is covered by an albumen-like layer, which is commonly referred to as egg white. This is and then an elongated membrane, and then that hard exterior shell. The hard shell is a source of calcium and minerals, which are added when the egg is still in the uterus before it is able to enter the cloaca, and then exits the bird’s body.

Cloaca is the sole posterior opening that is used for digestion as well as reproductive and urinary organs found in bird. It is located below the tail and covered in fur on the lower abdominal area. Birds transfer eggs out of inside the abdomen through this vent.

To allow eggs to be released easily, their sharper edge should be facing the vent. If the eggs aren’t in this orientation and the eggs appear large or too large, the bird might be unable to lay eggs and might require vet intervention. Particularly, parrots need up to three days to transport eggs from the ovary down the fallopian tube and then out the vent.

 Egg Fertilization Process  

Do birds receive an internal fertilization system or is it external? What happens to a fertilized bird’s egg? When it is released the egg’s insides are fertilized therefore an egg that’s already laid can’t be fertilized anymore. The process of fertilization for birds is carried out at a very early stage inside the fallopian tubes prior to the egg’s egg yolk and white covering the ovum. That is when the cells in the ovum are developing.

Fertilization takes place when males and females are able to mate prior to the release of the ovum through the fallopian tube. Male sperm may remain within the fallopian tubes for a couple of days before it reaches the female’s egg.

white and green egg on nest

If there is sperm inside the fallopian tubes during the moment of the division of the ovum the sperm will enter the ovum instantly to fertilize the eggs. The sperm is then able to travel through the remainder of the fallopian tube.

On the surface at a glance, there is no apparent distinct difference between an egg that is not fertilized and one that has been fertilized. If the female incubates eggs inside her nest and we witness the chicks forming and hatching, we can tell that the egg was fertilized from within.

 Artificial Insemination  

In certain instances, there may be a reluctance to breed between birds, which may cause unintended issues for farmers. Veterinarians can intervene through artificial insemination. They will take sperm and move to the cloaca female. This is a highly skilled process which is why farmers shouldn’t attempt to perform it on their own.

Verification of Fertilization

Like we said earlier, though it’s difficult to determine whether an egg has been fertilized or not by an eye alone, however, we can determine. You can determine whether an egg is fertilized by placing it under the light of a bright source and searching for blood vessels present for the duration of the embryo.

Sometimes, the embryo can appear as a shadow or a small black dot. It is recommended to use lighting that emits less heat so as to not affect the growth of the embryos of young birds.

NOTE: Many bird lovers are fascinated by the peculiar behavior of birds. If you do see the birds mating, it’s advised to remain away as getting too close to them could cause them to be scared and force them to go away. It could harm their relationship.


Are the eggs of birds fertilized prior to or after they’ve laid? The answer is now available! When the bird is at a point of mating its reproductive organs including the ovaries and testes are expanded and produce eggs and sperm.

Male birds store sperm inside their cloaca until their partner is found females will accept the substance in their cloaca prior to it being absorbed into their bodies to fertilize eggs and start egg development.

I hope that you enjoy this post about how birds’ eggs are fertilized interesting and informative. If you have questions or need more information on the fertilization of eggs in birds do not hesitate to contact us. our comments!


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