When you cook with eggs, keep a tally sheet on the counter, eggs with bulls-eyes are fertilized. When you get a high percentage - then you can set eggs with confidence.
I do not believe you can candle a fresh egg and see if it is fertilized. Only thing I have seen is when the embryo begins to develop after a week of being brooded either under a hen or in an incubator.
As Bobby says, chickens are different than mammals. In nature, birds lay an egg, and must wait about 24 hours to lay another. So they leave the first egg, only coming back to lay again. Then when the number of eggs looks right to the bird, the broody hormone kicks in, and then the bird begins to set. For chickens, after setting for 24 hours, bringing the eggs up to about 100 degrees for 24 hours, only then do the eggs begin to grow into embryos. Before that they are inert.
Now over centuries, humans began to keep hens that lay well, so they lay eggs when they have no intention of going broody. They lay them, they are fertilized, but will die if left in the nest. It is not until (the chicken gods, stars cross, and day length) things all line up, will a hen go broody. Often times she will do that whether or not the eggs are fertilized or not.
Long old post... but my point is, if you have a rooster, more than likely they are fertilized, but no moral question about eating them until they have been warmed for more than 24 hours. It takes quite a bit of experience to note the bulls eye.
Mrs K
