Courtship - Ospreys generally arrive on their breeding grounds in late March or early April. Juveniles spend about 17 months on the wintering gounds. Age at first reproduction varies not only among individual ospreys but among populations, apparently in relation to the availability of nest sites and other resources. Most resident ospreys lay their clutch in winter. The area around the nest is generally open, giving the birds clear access when landing.
Ospreys also prefer to nest over water for protection against climbing predators.
Islands free of mammalian predators allow safe nesting in low trees and even on the ground. Therefore, they generally catch only surface fish or those that frequent shallow flats and shorelines. Ospreys are opportunists. Predators exert a major impact on the nest sites ospreys choose. In the 1960's osprey populations declined as a result of DDT which were washed into water courses and ingested by fish.