Do you ever remember seeing your grandmother hold an egg up to the light before she started making breakfast? If you asked her why, her answer would have been “to make sure it’s not fertilized.” But is that a genuine concern when you buy eggs today? How do chicken eggs get fertilized anyway?

How Do Chicken Eggs Get Fertilized? As Simple As This!

Some people may be surprised to learn that a rooster is not necessary in order for a chicken to regularly lay eggs – only if those eggs are going to be fertilized. This means you don't need to worry about your store bought eggs (produced without the aid of a rooster). But this does beg the question, how do chicken eggs get fertilized?

Basically, a chicken will, on an almost daily basis, develop a new egg composed of yolk and albumin (egg white), then covered by a thin layer of shell. When a rooster is present and mates with the chicken, the chicken will store the deposited rooster sperm in a small internal pouch. As the newly forming egg passes by, it will be fertilized by this deposit of sperm. The egg will then develop the shell and be laid looking identical to an unfertilized egg.

The Detailed Explanation of How Do Chicken Eggs Get Fertilized

There Is a Bit More to It

That all sounds simple enough, but you could be forgiven for thinking: “surely there’s more to it than that!” And you’d be correct. So what is the full story behind the question “how do chicken eggs get fertilized?” Like any other animal, fertilization requires the production of an egg cell from the female and sperm from the male. The chicken’s reproductive system is essentially divided into two parts: the ovary (responsible for producing the egg yolks) and the oviduct (where the egg white, membranes and shell develop around the yolk). The fertilization process is much like an assembly line in a factory – so long as all the parts of the machine are functioning in the correct order, the end result will be the desired finished product.

The Journey Begins

The journey begins in the ovary, where the egg yolks develop and reach maturity. Once mature, the yolk will be surrounded by a membrane called the perivitelline, which stores nutrients and has a small white dot called a germinal disc, which is vital for the fertilization process.

Fertilization Occurs

After reaching maturity, the yolk will leave the ovary and travel to the first section of the oviduct, called the infundibulum. It is this area of the oviduct where sperm is stored after mating. As the yolk travels through the stored sperm will bind to the membrane, create a hole and then enter the yolk.

Move Along Now

After about 15 minutes in the infundibulum, the yolk will continue its journey through the oviduct, developing the egg white, membranes and shell.

The Little Miracle

The final stop on the assembly line is the actual laying of the (now fertilized) egg. At this stage, the fertilized egg has already developed approximately 20,000 embryonic cells and will, if incubated properly, eventually develop into a fully formed chick.


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  • toniSep.13 20:00
    my rooster it in and out of the pin does he need to stay in there or will he fertilize the egg at night
  • SandyJun.3 17:27
    R. Tuman...Seriously, there is the internet or the nature channel. What will you do after they are laid....raise them to eat??? The better lesson here would be, compassion!
  • R. TurmanMar.6 17:44
    We live in the city where the law allows for up to 6 hens, no roosters but I would love to have my grandchildren witness the Whole process of raising chickens. So I'd like to get a "rent-r-rooster" for a while to get fertile bunch of eggs for a brooding hen to set on. Any idea how long to have the rooster to with the hens. I'm thinking a week to ten days should do it. Any help here before the neighbors complain?
  • JamesFeb.5 01:11
    As a pastry chef I have found a few fertilised eggs from shop bought eggs. But that is maybe 3-4 in total out of 1000ish a week for 10 years so a very small amount. Also what is the cause of really bloody eggs? Not when there is a spot of red but completely red? Thanks
  • Barrie LewisJan.1 07:57
    How much semen can the hen store in her internal sac? Or, to put the question differently, how often must the rooster run with the hens? If you don't want a permanent rooster, they make too much damn noise at 4am, could you bring him once a month say to do his business?
  • Does a rooster have a penis?
  • P.WreckDec.15 10:56
    @ : Did anyone answer your question? If not how does he deposit sperm? ????
  • DeguFeb.18 23:18
    @ : Just passing by and noticed your questions. The rooster does not have a penis but instead he has a cloaca (not unlike the anal sphincter). The internal chamber passes semen from the testes to the opening and he rubs his cloaca against the females cloaca in order to deposit the sperm. Birds generally mate repeatedly to ensure this was a success.
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