Infertile eggs will have a blastodisc that will have an irregular shape and its white colour is very faint and foggy. All eggs will have a white spot or blastodisc whether or not it is fertile.
Find out by candling
If the egg is fertile, then you should see a dark spot around the middle of the egg, with some spider-like veins beginning to form around it. If its not, you should just be able to see the shape of the yellow yolk inside the egg, without any signs of an embryo or veins.
You'll see blood pumping through the heart of a tiny, developing embryo if you candle a fertile egg on Day 4. If the embryo dies at this point, you may still see a faint network of blood vessels inside the egg's contents. An embryo dying at this point will show a large, black eye.
All eggs were classified as 'infertile' when collected, but most were actually fertile with numerous sperm on the ovum. Eggs of captive birds had fewer sperm and were more likely to be infertile than those of wild birds.
In the normal situation, most psittacines or parrots will lay a clutch varying from 3-6 eggs, then sit on the eggs until they hatch. On occasion, a solitary bird may lay a clutch of eggs and then sit on them as if they were fertile. This is why many people recommend leaving the eggs in the cage with the bird.
Most cells aren't visible to the naked eye: you need a microscope to see them. The human egg cell is an exception, it's actually the biggest cell in the body and can be seen without a microscope.
Signs of development will typically appear as a dark spot surrounded with numerous blood vessels. If this is what you see, then congratulations, your egg is viable and contains a chicken embryo. An unfertilized egg will not show any development at this stage and will simply appear clear when candled.
The best kept secret in determining an egg's freshness is to see if it sinks in water. To try the egg water test, simply fill a glass or bowl with cold water and submerge the eggs. If the eggs sink to the bottom and lay flat on their side, they're still fresh.
A fresh egg should have a bright yellow or orange yolk and a thickish white that doesn't spread too far. If it's off, the yolk will be flatter and discoloured and the egg white will be far runnier. As we've already described, rotten eggs will also have a sulfuric smell to them.
The process of removing dead eggs while incubation is called 'Candling'. It involves shining a bright flashlight through the egg in a dark room. Upon close inspection, you'll see veins running through the egg in case it's alive. Hope you found it helpful!
Removing the eggs is the best policy. Wait until she is off the nest, and if she has vey recently laid them, say within the last 48 hours, you might want to replace them with plastic beads of the same size, or tiny wooden eggs if you can find some for sale at your local bird/pet store.
Early signs and symptoms include implantation bleeding or cramps, which can occur 5–6 days after the sperm fertilizes the egg. Other early symptoms include breast tenderness and mood changes.
Does moving the egg during candling damage it? No, as long as you're careful and as long as you don't candle after day 18 of incubation. You will generally need to turn the egg to see what's going on inside, particularly as you come to the later stages of incubation. Always take it slowly.
To know if the egg is a winner look for a network of blood vessels that appear white. A dark outline at the center of the blood vessels is the embryo. You may even see the dark eyes of the embryo or the embryo moving slightly. These are both telltale signs that the egg is a winner.
The human egg is 0.1 mm in diameter.
Do fertile eggs sink or float? Eggs sinking or floating is nothing to do with fertility – it's to do with freshness. The older an egg is, the more it will float. So a fresh egg will sink; the more it tilts upwards or even floats, the older it is.
She will hopefully give up on the eggs within 3-4 weeks. Some birds sit the duration of the incubation period and others get bored after the first week.
This is all fine and dandy if your chicken does have eggs to hatch, but sometimes, a chicken will sit on unfertilized eggs or even imaginary eggs. Hens raised without roosters can't lay fertile eggs, but they can still go broody and attempt to sit on a clutch of eggs.
Birds of larger species also take a bit longer to mature into successful egg laying. Immatures will occasionally lay eggs; these will almost certainly be infertile. However, unlike domestic chickens, wild birds do not constantly lay eggs (fertile or infertile).
Birds reproduce by internal fertilization, during which the egg is fertilized inside the female. Like reptiles, birds have cloaca, or a single exit and entrance for sperm, eggs, and waste. The male brings his sperm to the female cloaca. The sperm fertilizes the egg.
Originally done with a candle, egg candling is now done with a small, powerful flashlight that shines up and through the shell of the egg. You can use either a small, basic flashlight or an expensive, high-end machine to do your candling.