Why are bald eagles called bald if they have feathers on their heads?

Bald eagles are not actually bald. The term "bald" in their name historically meant "white-headed". This refers to the distinctive white feathers on the adult bald eagle's head, which contrast sharply with its dark brown body and wings. Young bald eagles do not develop these white head and tail feathers until they are about four to five years old. The bald eagle is unique to North America and is the national bird of the United States.1