I guess there are two answers to this question: one hi-tech answer and one low-tech answer.
The low-tech answer: A male is fertile when he can impregnate a female.
The high-tech answer: Conduct a semen analysis; combine findings for sperm count, motility, morphology, volume, sugar levels, pH, and so forth, and compare with normal levels. This is commonly done when a couple cannot conceive.
To answer your question in another way, human males become fertile by the process of puberty. There is no exact calendar date for when it starts and finishes, but the end product of puberty is normally a sexually mature, fertile person. On average, puberty sets in between 13-16 years of age, and can take anywhere from a few months to a few years to complete. I think it's usually done by the time you're 17 y.o., but for some it could be done as early as 10 y.o.
In order to tell if a chicken egg is fertile you need to crack it open into a bowl. Use a spoon to move around the yolk of the egg. Keep looking until you see a pale dot on the yolk. Look closely at it. If it is simply a dot, the egg is infertile. If it is a doughnut shape, it is fertile.
you can obsamen the egg and look for any little white lines this shows that on sertain places of the egg it is to thin this can course the egg to split or even have a living thing inside!
You could put the egg in the light to see.
Since the egg white is translucent, the yolk is not.
You could check if the egg is fertile without difficulty.
The best way to tell if eggs are gluggers is to candle them. Hold a flashlight behind them in a dark room. You should be able to see the veins or developing embryo if they are fertile.
The one way you can tell if a chicken eggs is fertile is by holding a strong flash light behind it and if you see the embero it is fertile
No, pufferfish will not lay non-fertile eggs. I have had multiple pufferfish for over 5 years and they haven't laid non-fertile eggs. Although she did mate with my other pufferfish and lay fertile eggs.
Parrot eggs are either fertile when they are laid or they are not fertile when they are laid. They have to be fertile and properly incubated in order to hatch.
Do you have a Rooster living with Hens? If so, chances are, yes, the eggs will be fertile. If the hen is brooding, meaning she is sitting on top of the egg to keep it warm, then it's probably fertile, if not, then it's not fertile. In any case should you have a rooster and a hen together, and the hen lays an egg, and it doesn't brood, then you should keep the egg warm. I think to check just hold the egg up to a light lol.
no
MY head
As long as they have a fertile rooster around who is breeding with them, they should certainly lay fertile eggs, though golden sex links only very rarely get broody and sit on eggs themselves.
If after 24 hrs the egg is not a white/opaque it probably is fertile.
No
Fertile eggs
After mating.