Osprey

The origins of osprey are obscure;[22] the word itself was first recorded around 1460, derived via the Anglo-French ospriet and the Medieval Latin avis prede "bird of prey," from the Latin avis praedae though the Oxford English Dictionary notes a connection with the Latin ossifraga or "bone breaker" of Pliny the Elder.^[23][24] However, this term referred to the bearded vulture.^[25]

The osprey differs in several respects from other

The sexes appear fairly similar, but the adult male can be distinguished from the female by its slimmer body and narrower wings. The breast band of the male is also weaker than that of the female or is non-existent, and the underwing coverts of the male are more uniformly pale. It is straightforward to determine the sex in a breeding pair, but harder with individual birds.[31]

The juvenile osprey may be identified by buff fringes to the plumage of the upperparts, a buff tone to the underparts, and streaked feathers on the head. During spring, barring on the underwings and flight feathers is a better indicator of a young bird, due to wear on the upperparts.^[29]

In flight, the osprey has arched wings and drooping "hands", giving it a gull-like appearance. The call is a series of sharp whistles, described as cheep, cheep, or yewk, yewk. If disturbed by activity near the nest, the call is a frenzied cheereek!^[32]

• 
  Eurasian osprey
  (P. h. haliaetus)
• 
  American osprey
  (P. h. carolinensis)
• 
  Caribbean osprey
  (P. h. ridgwayi)
• 
  Australasian osprey
  (P. h. cristatus)

The osprey is the second most widely distributed raptor species, after the

The osprey is piscivorous, with fish making up 99% of its diet.^[41] It typically takes live fish weighing 150–300 g (5.3–10.6 oz) and about 25–35 cm (9.8–13.8 in) in length, but virtually any type of fish from 50 g (1.8 oz) to 2 kg (4.4 lb) can be taken.^[27] Even larger 2.8 kg (6.2 lb) northern pike (Esox lucius) has been taken in Russia.^[42] The species rarely scavenges dead or dying fish.^[43]

Ospreys 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.^[44] They catch fish by diving into a body of water, oftentimes completely submerging their entire bodies. As an osprey dives it adjusts the angle of its flight to account for the distortion of the fish's image caused by refraction. Ospreys will typically eat on a nearby perch but have also been known to carry fish for longer distances.^[45]

Occasionally, the osprey may prey on rodents, rabbits, hares, other mammals, snakes, turtles, frogs, birds, salamanders, conchs, and crustaceans.^[43][46][47] Reports of ospreys feeding on carrion are rare. They have been observed eating dead white-tailed deer and Virginia opossums.^[48]

• 
• 
  American osprey with American gizzard shad
• 
  American osprey with scraps of fish on its beak
• 
  Eurasian osprey feeding on a fish in Kartung, the Gambia. Characteristically its tongue often pokes out whilst swallowing food.

The osprey has several adaptations that suit its piscivorous lifestyle. These include reversible outer toes,^[49] sharp spicules on the underside of the toes,^[49] closable nostrils to keep out water during dives, backward-facing scales on the talons which act as barbs to help hold its catch and dense plumage which is oily and prevents its feathers from getting waterlogged.^[50]

The osprey breeds near freshwater lakes and rivers, and sometimes on coastal brackish waters. Rocky outcrops just offshore are used in

Ospreys usually mate for life. Rarely, polyandry has been recorded.^[56] The breeding season varies according to latitude: spring (September–October) in southern Australia, April to July in northern Australia, and winter (June–August) in southern Queensland.^[51] In spring, the pair begins a five-month period of partnership to raise their young. The female lays two to four 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 are about 6.2 cm × 4.5 cm (2.4 in × 1.8 in) and weigh about 65 g (2.3 oz).^[51] The eggs are incubated for about 35–43 days to hatching.^[57]

The newly hatched chicks weigh only 50–60 g (1.8–2.1 oz), but fledge in 8–10 weeks. A study on Kangaroo Island, South Australia, had an average time between hatching and fledging of 69 days. The same study found an average of 0.66 young fledged per year per occupied territory, and 0.92 young fledged per year per active nest. Some 22% of surviving young either remained on the island or returned at maturity to join the breeding population.^[56] When food is scarce, the first chicks to hatch are most likely to survive. The typical lifespan is 7–10 years, though rarely individuals can grow to as old as 20–25 years.^{[citation needed]} The oldest European wild osprey on record lived to be over thirty years of age.^{[citation needed]}

• 
  Egg, collection of the Museum Wiesbaden
• 
  Hatchling chicks
• 
  5 week old chicks
• 
  Fledgling juvenile
• 
  Adult

European breeders winter in Africa.^[58] American and Canadian breeders winter in South America, although some stay in the southernmost U.S. states such as Florida and California.^[59] Some ospreys from Florida migrate to South America.^[60] Australasian ospreys tend not to migrate.

Studies of Swedish ospreys showed that females tend to migrate to Africa earlier than males. More stopovers are made during their autumn migration. The variation of timing and duration in autumn was more variable than in spring. Although migrating predominantly during the day, they sometimes fly in the dark hours, particularly in crossings over water and cover on average 260–280 km (160–170 mi) per day with a maximum of 431 km (268 mi) per day.^[61] European birds may also winter in South Asia, as indicated by an osprey tagged in Norway being monitored in western India.^[62] In the Mediterranean, ospreys show partial migratory behaviour with some individuals remaining resident, whilst others undertake relatively short migration trips.^[63]

Swedish ospreys have a significantly higher mortality rate during migration seasons than during stationary periods, with more than half of the total annual mortality occurring during migration.

The osprey has a large range, covering 9,670,000 km² (3,730,000 sq mi) in just Africa and the Americas, and has a large global population estimated at 460,000 individuals. Although global population trends have not been quantified, the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e., declining more than 30% in ten years or three generations), and for these reasons, the species is evaluated as Least Concern.^[1] There is evidence for regional decline in South Australia where former territories at locations in the Spencer Gulf and along the lower Murray River have been vacant for decades.^[37]

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,^[66][67] but osprey populations declined drastically in many areas in the 1950s and 1960s; this appeared to be in part due to the toxic effects of insecticides such as DDT on reproduction.^[68] The pesticide interfered with the bird's calcium metabolism which resulted in thin-shelled, easily broken or infertile eggs.^[34] 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.^[41] In South Australia, nesting sites on the Eyre Peninsula and Kangaroo Island are vulnerable to unmanaged coastal recreation and encroaching urban development.^[37]