Distribution and abundance of nesting ospreys in the United States

Nesting Ospreys (Pandion haliaetus) in the contiguous United States now number about 8,000 pairs. Five regional populations exist (in order of abundance): Atlantic Coast, Florida and Gulf Coast, Pacific Northwest, Western Interior, and Great Lakes. Pesticides severely impacted the populations in the northern portion of the Atlantic Coast (Boston to Cape May) and the Great Lakes, but both are now recovering. During recent years in the west, especially in the Western Interior, reservoirs have been responsible for a range expansion and, perhaps, a population increase. However, a strong fidelity to ancestral breeding areas (short dispersal distance) has slowed the range expansion. Unique introductions to distant reservoirs (from breeding populations) are now being made and followed with intense interest. Ospreys adapted to man, his structures, and many of his habitat changes, but proved sensitive to his chemical pollutants. These characteristics make the Osprey an excellent environmental indicator species.