Ospreys can be found by along the coasts of rivers, ponds, lakes or oceans. The nest or eyrie sight is usually found on top of a large tree with a dead top or on a snag, not far from water. The nests are big, made of branches and lined with bark, grasses, or other discarded objects they may find. Ospreys will use the same nest for years. Here is an osprey nest close to a pond I frequent. The snag that it is on is at least 60 feet tall.
Ospreys were endangered before the ban of DDT and other pesticides in 1972. These pesticides were found to compromise eggs by causing them to be too thin and unable to support an embryo to maturity. DDT sprayed, will get onto worms, beetles, or fish by contaminating their environments. The pesticide will accumulate in them, the birds eat the bugs or fish, and then become ill. The gradual contamination of the pesticide alters the birds calcium metabolism, which results in thinner eggs.
Read more here about the OSPREY.