Pandion haliaetus

Description

The osprey has a slender body, long, narrow wings, and long legs. It flies with a marked kink in its wings, making a characteristic M-shape when seen from below.

Plumage is bright white underneath, with dark brown patches at the carpal joints and a mottled dark brown necklace. Other identifying markings include a dark stripe through each eye, and a dark brown back. The feet are pale blue-gray, and the beak is black. Females often have darker plumage and a more defined necklace than their male counterparts. Juveniles resemble adults, but have a somewhat speckled appearance due to buff-colored tips on their dark brown upper-wing and back coverts and a less well-defined necklace. Juveniles also have an orange-red iris, rather than the yellow iris that is typical of adults. Juvenile plumage is replaced by adult plumage by 18 months of age.

Adult ospreys are 21-23 inches long, have a wingspan of 57-67 inches, and weigh 2.5-4.5 pounds. Females tend to be slightly heavier than males and to have longer wingspans.

Distribution and Habitat

Ospreys have a worldwide distribution, wintering or breeding on every continent except Antarctica. Regions where ospreys are particularly abundant include Scandinavia and the Chesapeake Bay region of the United States. They can live almost anywhere where there are safe nest sites and shallow water with abundant fish, including lakes, rivers, wooded swamps with open water, and shorelines, from cliffs to salt-flats.

There are four subspecies of ospreys, which are separated by geographic region. Pandion haliaetus carolinensis breeds in North America and the Caribbean, and winters in South America. P. h. haliaetus breeds in Europe, north Africa, and in Asia, north of the Himalayas, and winters in south Africa, India and the East Indies. The last two subspecies are non-migratory. P. h. ridgwayi resides in the Caribbean, with a range that extends from the Bahamas and Cuba to southeast Mexico and Belize. P. h. leucocephalus is found in Australia and the southwest Pacific.

Diet

The osprey is also known as the fish hawk, because it feeds almost exclusively on fish. It will take virtually any fish species available, with size being the only limiting factor. Ospreys have been observed taking other prey on occasion, including birds, reptiles and amphibians, and rodents.

"Fishing" is done on the wing, with the osprey flying 30-130 feet above the water. When a fish is spotted, the osprey hovers briefly, then dives toward the surface of the water. It swings its legs forward and bends its wings back just before plunging into the water and grabbing its prey. It then uses strong, almost horizontal wing beats to lift itself and its prey from the water. Once airborne, the osprey rearranges the fish in its feet, carrying it with one foot in front of the other so that the fish is facing forward. The fish is then taken to a perch to be eaten.

Reproduction

Non-migratory populations breed and winter in the same location, though they may wander several hours from their nest during the non-breeding season. These populations begin breeding between December and March. Migratory populations generally breed where winters are cold enough to drive fish into deep water where they are inaccessible. These populations begin breeding in April or May.

In migratory populations, males and females arrive at the nest site separately, the male often arriving several days earlier than the female. Both sexes collect materials for the nest, but the female does most of the nest building. Ospreys choose structures that can support a bulky nest and that are safe from ground-based predators. Over-water nest sites that are often used by ospreys include buoys and channel markers, dead trees and artificial nest platforms. Ospreys have also been known to nest on various man-made structures, such as power poles, duck blinds, communication towers, buildings and even billboards. Nests are typically constructed of sticks and lined with softer materials such as seaweed, kelp, grasses or cardboard. A wide variety of flotsam and jetsam may also be incorporated into osprey nests, including fishing line, plastic bags and nearly anything else that an osprey might find and can lift. Osprey pairs use the same nest year after year, but must spend some time each year repairing it and adding materials before eggs can be laid.

Once a pair has established a nest, the male begins to deliver food to the female. This feeding continues until the young fledge or the nest fails. Two to four eggs are laid over a period of several days, each 1 to 2 days apart. Both the male and female incubate the eggs, which hatch after approximately 40 days. The eggs hatch in the order in which they were laid. Chicks that hatch first are larger and have a competitive advantage over those that hatch later.

At hatching osprey chicks are covered in white down with brown streaks on the face, back, and wings. This is replaced by charcoal-colored down after approximately 10 days. Feathers begin to replace the down at approximately two weeks and fledging occurs after 48-76 days. After fledging, young ospreys begin to hunt on their own, but may continue to return to the nest to receive food from their parents for another two to eight weeks. Ospreys are sexually mature by their third year, but may not breed until age five in areas where nest sites are scarce.

Scientific Classification

phylum Chordata
subphylum Vertebrata
class Aves
order Falconiformes
family Accipitridae
genus & species Pandion haliaetus

Animal Diversity Web http://animaldiversity.org/accounts/Pandion_haliaetus/
ARKive http://www.arkive.org/osprey/pandion-haliaetus/

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