Eagle eggs are ready to hatch after around 35 days of incubation. About 4 days before hatching, the chick develops an egg tooth at the top of its bill. From inside the egg the chick uses the egg tooth to poke a hole in the membrane separating it from the air bubble at the top of the egg shell. Still inside the egg, the chick takes its first breath into the air bubble. From this first breath the chick gets a burst of energy to help it complete the hatching process.
The chick uses its egg tooth to scratch around the inside of the shell in a circular path. The scratches weaken the shell in a pattern all around the egg. This process is called pipping, and can take from one to two days. When pipping is completed the chick gives a few expansive bursts and the shell opens up. The chick is hatched!