This is because , it is used again and again , and every year more is added to the nest until it may soon become as large as 4 m deep , 2.5 m across and weigh 1 tonne . One nest in Florida was found to be 6.1 m deep , 2.9 m across , and to weigh 3 S. The nest is built out of branches , usually in large trees near water . The nest is the largest of any bird in North America ; it is used repeatedly over many years and with new material added each year may eventually be as large as 4 m deep , 2.5 m across and weigh 1 t ; one nest in Florida was found to be 6.1 m deep , 2.9 m across , and to weigh 3 S. The nest is built out of branches , usually in large trees near water .