As its other common names suggest, the osprey's diet consists almost exclusively but not only of fish. It possesses specialised physical characteristics and exhibits unique behaviour to assist in hunting and catching prey. As a result of these unique characteristics, it has been given its own taxonomic genus, Pandionand family, Pandionidae. Four subspecies are usually recognized, one of which has recently been given full species status (see below). Despite its propensity to nest near water, the osprey is not classed as a sea eagle.
The osprey is 0.9–2.1 kg (2.0–4.6 lb) in weight and 50–66 cm (20–26 in) in length with a 127–180 cm (50–71 in) wingspan. It is, thus, of similar size to the largest members of the Buteo or Falco genera. The subspecies are fairly close in size, with the nominate subspecies averaging 1.53 kg (3.4 lb), P. h. carolinensis averaging 1.7 kg (3.7 lb) and P. h. cristatus averaging 1.25 kg (2.8 lb). The wing chord measures 38 to 52 cm (15 to 20 in), the tail measures 16.5 to 24 cm (6.5 to 9.4 in) and the tarsus is 5.2–6.6 cm (2.0–2.6 in). 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. Also adult male ospreys have a bright white chest area, while adult females have a white chest also but has brown, black, and gray speckling on that chest. It is straightforward to determine the sex in a breeding pair, but harder with individual birds. 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 upper parts. 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!
Distribution and Habitat Edit
The osprey is the second most widely distributed raptor species, after the peregrine falcon. It has a worldwide distribution and is found in temperate and tropical regions of all continents except Antarctica. In North America it breeds from Alaska and Newfoundland south to the Gulf Coast and Florida, wintering further south from the southern United States through to Argentina. It is found in summer throughout Europe north into Ireland, Scandinavia, Finland and Scotland, England, and Wales though not Iceland, and winters in North Africa. In Australia it is mainly sedentaryand found patchily around the coastline, though it is a non-breeding visitor to eastern Victoria and Tasmania. There is a 1,000 km (620 mi) gap, corresponding with the coast of the Nullarbor Plain, between its westernmost breeding site in South Australia and the nearest breeding sites to the west in Western Australia. In the islands of the Pacific it is found in the Bismarck Islands, Solomon Islands and New Caledonia, and fossil remains of adults and juveniles have been found in Tonga, where it probably was wiped out by arriving humans. It is possible it may once have ranged across Vanuatu and Fiji as well. It is an uncommon to fairly common winter visitor to all parts of South Asia, and Southeast Asia from Myanmar through to Indochina and southern China, Indonesia, Malaysia and the Philippines.
Behavior and Ecology Edit
Fish make up 99% of the osprey's diet. It typically takes fish weighing 150–300 g (5.3–10.6 oz) and about 25–35 cm (9.8–13.8 in) in length, but the weight can range from 50 g (1.8 oz) to 2 kg (4.4 lb). Virtually any type of fish in that size range are taken. 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 (33–131 ft) above the water, after which the bird hovers momentarily then plunges feet first into the water. Occasionally, the osprey may prey on rodents, rabbits, hares, amphibians, other birds, and small reptiles.
The osprey has several adaptations that suit its piscivorous lifestyle :
- Reversible outer toes,
- Sharp spicules on the underside of the toes
- Closable nostrils to keep out water during dives, and
- Backwards-facing scales on the talons which act as barbs to help hold its catch.
- Dense plumage which is oily and prevents its feathers from getting waterlogged.