The eagle's ability to see detail at a distance is extraordinary. Its vision is binocular, which means it is capable of altering focus from two feet to two miles. The eagle's skull has a feature called supra-orbital ridges which are bony extensions that overhang the eyes and help protect them from injury when the eagle is catching and handling prey. They also shield the eyes, like sun visors, reducing glare. The eyes are fixed in their sockets, so the eagle has to turn its whole head to look around.
Eagles mate for life and return to the same nest every year.
The female lays one to three eggs which hatch in 35 to 40 days. Eggs are usually laid several days apart and the chicks hatch at different times. The first chick will be fed by the parents for several days before its sibling hatches and will, therefore, have a significant size and weight advantage over the younger chick. In years when the parents are unable to bring sufficient food for both chicks, the older chick bullies the younger and weaker one until it dies of starvation. This behavior ensures that in years when food supplies run short, the older chick, at least, can be raised successfully.