The Osprey is a large fish-eating bird of prey with a cosmopolitan range. It has deep, glossy brown upperparts, while its breast is white and sometimes streaked with brown, and the underparts are pure white. The head is white with a dark mask across the eyes, reaching to the sides of the neck. The irises of the eyes are golden to brown, the bill is black, with a blue cere, and the feet are white with black talons. A short tail and long, narrow wings with four long, finger-like feathers, and a shorter fifth, give this bird a very distinctive appearance.
Ospreys have a worldwide distribution and are found in temperate and tropical regions of all continents except Antarctica. In North America they breed from Alaska and Newfoundland south to the Gulf Coast and Florida, wintering further south from the southern United States through to Argentina. They are found in summer throughout Europe north into Ireland, Scandinavia, Finland, and Great Britain though not Iceland, and winters in North Africa. In Australia, ospreys are mainly sedentary, though they are non-breeding visitors to eastern Victoria and Tasmania. These birds tolerate a wide variety of habitats, nesting in any location near a body of water providing an adequate food supply. They can be found near rivers, lakes, reservoirs, oceans, lagoons, coastal wetlands, estuaries, reefs, swamps, mangroves and marshes.
Ospreys are generally solitary birds but in winter they may roost in small flocks at night. As their other common names suggest, the diet of these birds consists almost exclusively of fish. They possess specialized physical characteristics and exhibit unique behavior to assist in hunting and catching prey. Ospreys hunt by day; they have a vision that is well adapted to detecting underwater objects from the air. Prey is first sighted when the osprey is 10-40 m (33-131 ft) above the water, after which the bird hovers momentarily and then plunges feet first into the water. When the prey is caught, ospreys fly to a tall perch where they can eat their meal. These birds communicate with each other using a series of sharp whistles, described as 'cheep, cheep' or 'yewk, yewk'. If disturbed by activity near the nest, their call is a frenzied cheereek!
Ospreys are monogamous and usually mate for life. Rarely, polyandry (one female to several males) has been recorded. The breeding season varies according to latitude; in southern Australia, it occurs in spring (September-October), in northern Australia from April to July and in southern Queensland in winter (June-August). In spring the pair begins a five-month period of partnership to raise their young. Ospreys nest near freshwater lakes and rivers, and sometimes on coastal brackish waters. The nest is a large heap of sticks, driftwood, turf, or seaweed built in forks of trees, rocky outcrops, utility poles, artificial platforms, or offshore islets. The female lays 2 to 4 eggs within a month and relies on the size of the nest to conserve heat. The eggs are whitish with bold splotches of reddish-brown and weigh about 65 g (2.3 oz). The eggs are incubated for about 35-43 days to hatching. The newly hatched chicks weigh only 50-60 g (1.8-2.1 oz) but fledge in 8-10 weeks. They become independent from their parents 2-3 months later and reach reproductive maturity when they are 3 to 5 years old.
In the late 19th and early 20th centuries, the main threats to osprey populations were egg collectors and hunting of the adults along with other birds of prey, but osprey populations declined drastically in many areas in the 1950s and 1960s; this was caused in part due to the use of pesticides such as DDT on reproduction which resulted in thin-shelled, easily broken or infertile eggs. Possibly because of the banning of DDT in many countries in the early 1970s, together with reduced persecution, the osprey, as well as other affected bird of prey species, have made significant recoveries. At present, in South Australia, nesting sites on the Eyre Peninsula and Kangaroo Island are vulnerable to unmanaged coastal recreation and encroaching urban development.
According to the IUCN Red List, the total osprey population size is around 100,000-499,999 mature individuals. The European population consists of 8,400-12,300 pairs, which equates to 16,700-24,600 mature individuals. Overall, currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are increasing.