The Osprey [Pandion haliaetus]

Feb 17, 2019 Features / Columnists, Interesting Creatures in Guyana

The osprey (Pandion haliaetus), sometimes known as the fish eagle, sea hawk, river hawk, or fish hawk, is a diurnal, fish-eating, bird of prey. It is a large raptor, reaching more than 60 cm (24 in) in length and 180 cm (71 in) across the wings. It is brown on the upperparts and predominantly greyish on the head and under-parts.
The osprey tolerates a wide variety of habitats, nesting in any location near a body of water providing an adequate food supply. It is found on all continents except Antarctica; although in South America, it occurs only as a non-breeding migrant.
As its other common name suggests, the osprey’s diet consists almost exclusively of fish. It possesses specialized 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, Pandion and family, Pandionidae. Four subspecies are usually recognized, one of which has recently been given full species status.
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 under-parts 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 under-wing coverts of the male are more uniformly pale. 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 under-parts, and streaked feathers on the head. During spring, barring on the under-wings and flight feathers is a better indicator of a young bird, due to wear on the upperparts.
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!
Fish make up 99 percent 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.
The osprey is particularly well adapted to this diet, with 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.
Occasionally, the osprey may prey on rodents, rabbits, hares, amphibians, other birds, and small reptiles. [Source: Wikipedia]

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