Eagles build their nests, or eyries, using sticks, branches, and other natural materials. The nests are typically located high up in trees or on cliffs, and may be used for many years by the same pair of eagles. Eagles may add to their nests each year, making them larger and more elaborate over time. Some eagle nests can reach enormous sizes, measuring up to 10 feet (3 meters) in diameter and weighing up to 2,000 pounds (907 kg).