The following material is adapted with permission from a fact sheet produced by the Hawk Mountain Sanctuary in eastern Pennsylvania.
The current world population of ospreys is estimated at fewer than 100,000 birds. In 2001, the number of breeding pairs in the lower 48 United States was estimated at between 16,000 and 19,000.
In the 1950s and 1960s, osprey populations decreased and the species was extirpated from many areas due to the effects of organochlorine pesticides like DDT. When ospreys consume fish containing pesticides such as DDT, these chemicals accumulate in their fatty tissues. DDT and other organochlorine pesticides compromise reproductive success by causing eggshell thinning. Osprey populations have increased in the United States since the late 1970s. Numbers increased primarily due to a ban on the widespread use of DDT in 1972.
Today, osprey numbers in the United States are increasing and individuals are returning to formerly vacated breeding grounds, as well as expanding into new areas. Restoration efforts involving reintroduction programs, as well as the provision of artificial nest sites, aided in the osprey’s recovery. Artificial nest platforms provide increased numbers of available nest sites and offer sturdy, safe nesting locations. Today, many osprey populations nest almost entirely on artificial nest sites.
Ospreys continue to be shot in some parts of their range, particularly at fish farms in Latin America and South America. Although ospreys tolerate human activity, excessive disturbance can disrupt nesting. Collisions with vehicles and power-lines also are sources of mortalities. Electrocution is another threat to ospreys around power-lines. Environmental contaminants continue to be a potential source of fatalities as well.