I’m not going not argue with what anyone said, to a certain extent I agree with most of what has been said. One of your goals is to have as few duds in the incubator as possible. I’ll work with that.
Just because a cockerel may not fertilize each and every hen in the flock (true, especially if you have more mature hens) doesn’t mean he doesn’t fertilize any before he fully matures. You’ve seen that he is fertilizing some by your egg for breakfast.
There are two ways I’m aware of for us to determine if an egg is fertile, crack it and look for the bull’s eye or incubate it and see if it develops. You can also do DNA testing but I’ll try to stick to practical solutions. If you crack an egg you can’t incubate it and once you start incubating you are kind of stuck. You cannot unincubate an egg.
If you can tell which hen is laying which egg, then just put the eggs from the hens that are laying fertile eggs in the incubator. The way it works the eggs are generally fertile for two weeks after a successful mating, so if one of her eggs is fertile the others she is laying should be also. That should greatly minimize your chance of getting duds. It will not eliminate those chances, there are several reasons eggs do not develop besides fertility, but it certainly helps.
Another way would be to wait until all the eggs you crack are fertile, but who knows how long you’ll have to wait for that.
You will often see recommendations to not incubate pullet eggs. When a pullet first starts laying it sometimes takes her a while to get all the different parts of her internal egg making factory working properly so the egg is put together in a way that it will hatch. That’s why you can get so many weird eggs when they first start laying. It’s a complicated system, perhaps the surprise is that so many get it right to start with. A lot of the time those first eggs are pretty small too. That size can cause problems. I hatch pullet eggs all the time, often fertilized by cockerels less than a year old. I’ve found that it’s best to wait until at least a month after they start laying before you incubate the eggs. Yours have been laying well past that month, you should be OK from that perspective.
While I do try for success, I often find the best time to do something is not necessarily when conditions are perfect, but when I can. For example, if I waited for perfect conditions to plant my early cool-weather garden, I’d skip some years because conditions are never ideal. I just do the best I can.
To sum up, if you can determine which hen is laying which egg and only incubate the eggs from obviously fertile hens, you minimize your chances of one not developing. That’s often easier said than done.
