Osprey nesting season varies across North America based on climate. Osprey eat fish so they nest near lakes, bays, deep rivers and sheltered salt-water. As with all birds, they migrate if their food supply is seasonal. Fish migration (salmon and shad) and ice (which makes fish inaccessible) are determining factors.
Osprey reuse the same nest year after year by adding to the top of it, but they won't return to the site until the ice is out. In South Florida osprey don't need to migrate so they begin nesting in November and December. In southern New England, they nest in mid-to-late April because the ice doesn't break until March. Timing in Western Pennsylvania is similar to southern New England's.
No matter where osprey nest, the process takes the same length of time: 37 days from egg-laying to hatch, 50-55 days from hatch to fledge, and 10-20 more days until the young are independent of their parents.
By now, the babies from this Shenango Lake nest have flown and they're learning the ropes of adulthood. When the cold weather comes it'll be their turn to go away.
(photo by Cris Hamilton)