If your hens have never been in the presence of a rooster or had contact with rooster sperm, then the eggs they lay should not be fertile. However, it is possible for hens to lay eggs that have a bullseye-like appearance even if they have not been fertilized. The presence of the bullseye does not necessarily indicate that the egg is fertile. Some hens can produce eggs with double yolks, which can give the appearance of a bullseye. Additionally, aging, hormonal changes, or changes in the hen's diet can also cause the bullseye-like appearance.
It's important to note that if the egg has been incubated, regardless of whether it was intentionally or not, it may develop into a chick. The bullseye is an indication that the egg has been fertilized, and if it is incubated, a chick can develop. Therefore, it is important to collect eggs frequently, especially in hot weather, to prevent accidental incubation from occurring.
If you're still concerned about whether or not your eggs are fertile, it may be helpful to look for eggs without a bullseye or pasteurize the eggs before consumption.