If you come across a bird egg, there are a few ways to tell if it is alive. One way is to candling the egg. This is done by holding the egg up to a bright light source, such as a flashlight. If the egg is alive, you should be able to see movement and blood vessels inside the egg. Another way to tell if an egg is alive is by feeling it. A live egg will feel warm, while a dead one will feel cold. You can also gently tap on the shell of an egg. A live egg will have a solid sound, while a dead one will have a dull sound.