North American Indians incorporated the eagle's primaries and tail feathers into their ceremonies and legends. Respiratory system - Eagles have external nares opening on both sides of the bill. A bald eagle never reaches speeds that would interfere with normal breathing. The eagle's lungs and air sac system is adequate for its size. Air moves in through the lungs and on into the air sacs before moving back through the lungs and out again.
Air passes through the lungs two times with each breathing cycle - twice that of mammals.
Beak - The hook at the tip is used for tearing. Behind the hook, the upper mandible, the edge sharp enough to slice tough skin, over laps the lower, creating a scissors effect. A bald eagle's beak is a strong weapon, but is also delicate enough to groom a mate's feathers or feed a small portion of food to a newly hatched chick. The beak and talons grow continuously, because they are made of keratin, the same substance as our hair and fingernails. The beak of a captive eagle is not warn down naturally, so must be trimmed annually.