How can you tell if a cockatiel egg is fertial?

bought my cockatiel from pet store she had a mate they sold her
mate. i don't know if the will hatch. how long when they mate does it take for her to lay eggs
Answers:
usually 2-3 days if she lays an egg. You probably do not want to be raising a chick if it is your first bird. Plus, with only one parent, it is very hard on the moether. If she lays an egg, just shake it up right after she lays it- you do not want to remove them or she will keep laying more, but shaking it will cause the embryo (if fertile) not to grow, and will do nothing if infertile (at this point it is only a couple cells- nothing more than you would get from a fertilized egg that you crack open and eat).

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a week or so you can tell if the egg is good by holding up to the sun if its live you should see some dark blood like stuff also if the egg is cold is cactus. hope i helped

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It is difficult to say. Mating does not guarantee fertility. Also, how old is the cockatiel? If it isn't mature she isn't going to lay an egg at all. Sometimes even mature tiels don't lay.

You can tell if there is an embryo by "candling" the egg. Holding it up to bright light to see if there is anything in it.

There are also machines you can buy that tell if your egg has a heart beat called a "Buddy". This will probably be the best thing to tell if it is fertile and alive.