The Eagle.

The eagle is the bird with greater longevity of these species. He gets to live 70 years, but to reach that age, at 40, he must take a serious and difficult decision.
At 40, his nails are tight and flexible and he can not take his prey on which he feeds. Its long, pointed beak curves, pointing against its chest. Their wings are aged and heavy and their feathers are thick.
Flying is already so difficult!
So, the eagle has only two alternatives: to die or face a painful renewal process that will last 150 days. This process consists of flying to the top of a mountain and staying there, in a nest close to a wall, where there is no need to fly.
After finding that place, the eagle begins to hit its beak on the wall until it is able to pull it out. Then he must wait for the growth of a new one with which he will detach one by one his nails. When the new nails begin to be born, it will begin to pluck its old feathers. After five months, he leaves for his renewal flight ... to live 30 more years.