Sweetpea1, Chicken breeds are not natural, they are all manmade. People, either a person like the lady that developed the Buckeye or a group that developed the Ameraucana, decide on certain traits and selectively breed until they get what they want. The natural state of chickens is barnyard mix, not a specific breed. A breed is not defined by genetics, it’s defined by appearance. Look at any Standard of Perfection (SOP). The SOP is the written agreed appearance of a certain breed. It’s what the judge sees, and he cannot see the individual genes.
The rooster has no effect on what the egg the hens lay looks like. That’s all controlled by genetics. The hen will lay an egg that looks the same even if there is no rooster around. He will contribute genetics to his daughters so he does have a big effect on what the eggs his daughters lay look like. If your hens are laying greenish eggs, it has nothing to do with that rooster.
Basic egg shell color genetics are pretty simple. There is one gene pair that controls whether the base color is blue or white. Blue is dominant so if just one of those genes in that gene pair is blue, the base color will be blue. That gene can come from either the mother or the father. Brown and green are just brown on top of either white or blue. You can tell what the base color of your eggs is by breaking an egg and removing that membrane on the inside. You’ll either see white or blue. There is one gene that can cause the shell of a white egg to have a slight pinkish tint throughout, but it is really clear whether the egg is based white or blue.
I don’t know what you mean by greenish tint. You need to look at the inside of the shell to see the base color. If it is blue, that color is already genetically in your hens. If not, that greenish is just your interpretation of a certain shade of brown.
A complication comes in because there are a lot of different genes that affect the shade of brown. Some are dominant, some recessive, some partial or incomplete dominant, some only have an effect if another specific gene is present. One is even sex linked, if he has it the rooster can give it to his daughters but the hen cannot give it to her daughters. That’s why you can get so many different shades of brown or green, there are a tremendous number of possible combinations. But the base color remains either blue or white.
Every chicken breed, or breed of dogs or cattle for that matter, were developed by inbreeding. Every prize winner at any major chicken show was developed by inbreeding. That can be parent to offspring, sibling to sibling, or cousin to cousin. A fairly common model is to breed a superior parent to its offspring to enhance certain traits until you get pretty much what you want. This eliminates a lot of genetic diversity which is what you want for those specific traits but you don’t want to eliminate other aspects of genetic diversity. These other traits are the ones that Nchls School was talking about. So once they get about what they want they often revert to cousin to cousin, like in spiral breeding, to help maintain a certain genetic diversity. Someone who is developing a breed needs to know what they are doing.
If your flock becomes too inbred productivity and fertility can drop. They might become more susceptible to diseases. There are potential problems with inbreeding but people do it all the time.
As an aside, I’ve discussed breeding parent to offspring versus breeding siblings with one of the genetics experts on here. As far as pure genetic diversity there is no difference in breeding parent to offspring versus brother to full sister. That’s often misstated on here. The reason you normally breed a superior parent to its offspring is that method enhances the traits that make the parent superior. Sibling to sibling, it’s more random.
For thousands of years small farmers have been keeping flocks that feed their family with meat and eggs and have inbred flocks. Extremely few understand the details of how genetics work yet they are able to keep genetic diversity up to a good level. There are a few tricks to that. First, don’t let inferior chickens breed. If you have a deformed chicken don’t breed it. If a hen lays bad eggs, don’t hatch the ones she does lay. Keep as your breeders the ones that you want your chickens to be like. Another trick is that every few generations, bring in a new rooster that has been isolated genetically for several generations. The larger your breeding flock the less often that has to be, but every four to five generations usually works.
By selecting your breeders you can pretty much breed out any colors or any traits you can recognize you don’t want if you have a genetic mix to start with. If you hatch eggs only from hens that go broody, after a few generations you’ll have a flock where a lot of your hens go broody. If you only hatch eggs from hens that don’t go broody you will have a flock where hens seldom go broody. It’s hard to breed that totally in or out of a flock but you can certainly strongly influence a trait like that. If you want a red flock, don’t breed black chickens. If you want a flock that lays big eggs, don’t hatch small eggs. If you want green or blue eggs, hatch green or blue eggs. You can strongly influence the direction your flock takes by selecting your breeding chickens. But every time you bring in a news rooster to get the genetic diversity back up you lose some uniqueness to your flock. By making your flock special you are removing genetic diversity. That’s OK up to a point but after a while it can be bad.
I don’t know if I answered your questions or not. Hopefully you will get something useful out of this. Good luck!