Osprey

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Image:Osprey.jpg

Common Name: Osprey
Scientific Name: Pandion haliaetus

Size: 24 inches (60 cm); Wingspan: 71 inches (180 cm)

Habitat: Worldwide; it is found on all continents except Antarctica. Individuals in the tropics and subtropics are resident, but others migrate to the lower latitudes of the Amazon Basin, South America’s northern coast, or West Africa in the non-breeding season. Migrants begin moving to lower latitudes in August and arrive by October, returning in March and April. Birds are generally solitary and usually migrate alone, but may congregate in small groups at roosts or plentiful food sources. The species migrates on broad fronts and is not dependent on land bridges during migration; birds readily cross bodies of water using flapping flight, but can soar easily over land. It is entirely diurnal.

It inhabits the areas around shallow waters, being sufficiently tolerant of human settlement to persist in suburban and sometimes urban environments.

Status: Least Concern. Global population: 500,000 adult individuals with an increasing population trend. Human persecution was the main historical threat, prevalent from the 18th-20th centuries. A combination of deforestation and the collection of eggs and live birds drove the species extinct in Azerbaijan. In the U.S.A. (and to a lesser extent elsewhere), numbers fell significantly from 1950-1970 as a result of pesticide use, although they are now recovering, as they are in Scotland where the species had been extirpated by collection and hunting. Pesticide use has now been reduced to a minor threat, but shooting still affects many birds on migration in the Mediterranean, notably in Malta. A few Australian birds are apparently impacted by local human disturbance. It is very highly vulnerable to the effects of potential wind energy development.

Diet: Fish make up 99% of the osprey's diet. Osprey may prey on rodents, rabbits, hares, amphibians, other birds, and small reptiles.

Ospreys have vision that is well adapted to detecting underwater objects from the air. Prey is first sighted when the osprey is 10–40 m above the water, after which the bird hovers momentarily then plunges feet first into the water. Ospreys, however, are unable to dive deeper than 1 m (3 feet) in water so shallow fishing grounds are preferred. Several studies have shown that ospreys caught fish on at least 1 in every 4 dives, with success rates sometimes as high as 70 percent. The average time they spent hunting before making a catch was about 12 minutes.

Nesting: The upperparts are a deep, glossy brown, while the 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, and the transparent nictitating membrane is pale blue. 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 it a very distinctive appearance. 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.

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.

Ospreys usually mate for life. 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. In spring the pair begins a five-month period of partnership to raise their young. Breeding areas are near freshwater lakes and rivers, and sometimes on coastal brackish waters. Rocky outcrops just offshore are used in coastal areas. The nest is a large heap of sticks, driftwood and seaweed built in forks of trees, rocky outcrops, utility poles, artificial platforms or offshore islets.

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. The eggs are incubated for about 5 weeks to hatching.

Cool Facts: The osprey is sometimes known as the sea hawk, fish eagle, river hawk or fish hawk. The osprey differs in several respects from other diurnal birds of prey. Its toes are of equal length, its tarsi are reticulate, and its talons are rounded, rather than grooved. The osprey and owls are the only raptors whose outer toe is reversible, allowing them to grasp their prey with two toes in front and two behind. This is particularly helpful when they grab slippery fish.

There are 4 subspecies of Osprey:

  • P. h. haliaetus, first described by Linnaeus in 1758. The nominate species; found in the Palearctic.
  • P. h. carolinensis, first described by Gmelin, 1788. Found in North America. This form is larger, darker bodied and has a paler breast than nominate species.
  • P. h. ridgwayi, first described by Maynard in 1887. Found in the Caribbean islands. This form has a very pale head and breast compared with nominate species, with only a weak eye mask. It is non-migratory.
  • P. h. cristatus, first described by Vieillot in 1816. The “Eastern Osprey”; found on the coastline and some large rivers of Australia and Tasmania. The smallest and most distinctive subspecies, also non-migratory.

In Greek mythology, Nisos, a king of Megara became an osprey to attack his daughter after she fell in love with Minos, King of Crete.

The osprey is depicted as a white eagle in heraldry, and more recently has become a symbol of positive responses to nature.

An Osprey may log more than 160,000 migration miles during its 15-to-20-year lifetime. Scientists track Ospreys by strapping lightweight satellite transmitters to the birds’ backs. The devices pinpoint an Osprey's location to within a few hundred yards and last for 2-3 years. During 13 days in 2008, one Osprey flew 2,700 miles—from Martha's Vineyard, Massachusetts, to French Guiana, South America.


This 3D model is found in Songbird ReMix Birds of Prey Volume III: Hawks of the New World

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