Bald eagles build the largest nests of any North American bird . . . [VID: Did you know? Bald eagles mate for life. When they are 4 to 5 years old, they choose a mating partner through courtship rituals including calls and aerial displays. The pair will build their home in a large tree near a body of water. They create their nests, called eyries, out of sticks. These eyries are enormous. They can exceed 8 feet wide and 12 feet deep. They can weigh up to 2 tons. Bald eagles build the largest nest