My mother is a canary breeder, and canary eggs usually hatch on the 13th day. Around day 12 it's a good idea to either give the mother bird a bath, or spritz the eggs lightly with water from a spray bottle. This helps soften the shell, making it easier for the baby to hatch. Also, around day 10ish, you can place the egg in water, and if the egg bobs around, it's actually the baby bird moving around inside. If you want to know if the egg is fertile before that, you can candle the egg. Around day 4 or 5 you can usually tell by candling if you have a fertile egg. Of course, you need to be very gentle. If you candle and all you see is clear, with a bit of yellow yolk, you don't have a fertile egg. If the egg seems more solid, and you can see red "veins" through it, you have a fertile egg.