Breeding pairs are usually on the nest by mid March in more southerly parts of their breeding range and late April farther to the north. Ospreys will take advantage of just about anything affording a view of the water to build their nests, including tall trees, cliffs, buoys, telephone poles, the sides of bridges, and even wrecked ships. The bulky nest is constructed of rough sticks. Building material may be added each season for decades, by successive pairs of birds, resulting in a structure five or more feet in diameter and several feet thick. The female usually lays three eggs, which must be incubated for five weeks.
Osprey eggs are whitish with reddish spots.
The female sits on the eggs most of the time, with the male doing egg duty occasionally while the female is fishing. Once the eggs hatch, the male does all the fishing for about six weeks, after which both work to feed the hungry chicks. After only 10 weeks or so, the young birds have all their flight feathers. The DDT doesn't break down or get excreted along the way, and the result is an osprey sick with a big load of DDT, and in particular, eggshells too thin to survive incubation. Happily, DDT was banned in the US in 1972, and since then many of our birds of prey have begun to recover, including the bald eagle, peregrine falcon, and the osprey.