Osprey (Pandion haliaetus): Facts, Diet, Nests and Migration

What does an osprey look like?

An adult osprey is dark brown above and bright white below. The head is white with a broad dark stripe running from the yellow eye back to the neck, like a mask. Many birds, especially females, have a band of brown streaks across the chest, often called a necklace.

In flight the osprey is easy to recognize once you know what to look for. Its wings are long and narrow and are usually bent at the wrist, which gives the bird a shallow M shape against the sky, a little like a large gull. Under the wing there is a dark patch at each wrist, and the flight feathers and short tail are finely barred.

The bill is black and strongly hooked, and the feet are pale gray to white with long, black, curved talons. Young ospreys look like adults but have pale buff edges to the brown feathers on their back, which makes them look scaly, and orange-red eyes rather than yellow ones.

How big is an osprey?

The osprey is a medium-large raptor, bigger than a red-tailed hawk or a common buzzard but much smaller than an eagle. Females are larger and heavier than males, as in most birds of prey.

Ospreys from North America average a little heavier than European birds, and the ospreys of Australia, sometimes treated as a separate species called the eastern osprey (Pandion cristatus), are the smallest.

Classification: a family of its own

For a long time scientists argued about where the osprey belongs. Its feet and hunting method are so unusual that it is now placed in its own family, Pandionidae, with no other living members. The closest relatives are the hawks, eagles and kites of the family Accipitridae, and DNA studies suggest the two lines separated tens of millions of years ago.

Most authorities recognize four subspecies that differ only slightly in size and color: the Eurasian osprey, the North American osprey, the pale Caribbean osprey and the Australasian osprey. The osprey is one of very few land birds found almost worldwide.

Habitat and range

Ospreys live wherever there is shallow, clear water with plenty of medium-sized fish and a safe place to build a nest. That includes lakes, rivers, reservoirs, estuaries, salt marshes, mangroves and rocky coasts.

• North America: breeds from Alaska and Canada south across much of the United States, with large populations on the Atlantic coast, around Chesapeake Bay, in Florida and in the Pacific Northwest. Most birds winter in Central and South America.
• Europe: breeds mainly in Scandinavia, Finland, Germany, Poland, the Baltic states, Russia and Scotland, with smaller numbers in England, Wales and around the Mediterranean. Most winter in Africa.
• Asia, Africa and Australia: scattered breeding populations from Siberia and Japan to the Middle East, the Red Sea, parts of Southeast Asia and the coasts of Australia.

In South America the osprey is only a winter visitor and does not breed. Birds in the Caribbean, Florida, Australia and parts of the Mediterranean are largely resident, while northern populations migrate. Read more in where do ospreys migrate?.

Diet and hunting

Fish make up about 99 percent of an osprey’s diet, which is unusual even among fish-eating birds. Ospreys take almost any species that swims near the surface, such as pike, trout, perch, carp, mullet, herring, menhaden and flounder. Most prey weighs about 150–300 g (5–11 oz), but ospreys can take fish of up to 2 kg (4.4 lb) or so.

The osprey hunts by flying slowly over the water at about 10–40 m (30–130 ft), often hovering briefly when it spots a fish. It then folds its wings, swings its feet forward and hits the water talons-first, sometimes disappearing completely below the surface. Because it can reach only fish in the top meter or so (about 3 ft), it depends on shallow water and calm conditions.

Several features make this possible. The outer toe can turn backward, so the bird can hold a fish with two toes in front and two behind, as owls do. The soles of the feet are covered in sharp spiny scales that grip slippery skin, the nostrils can close underwater, and the dense, oily plumage sheds water quickly. After takeoff the osprey shakes itself in mid-air like a wet dog and turns the fish head-forward to reduce drag. Full details are in how do ospreys catch fish?.

Behavior and communication

Ospreys are active by day and spend much of their time perched on a dead tree, post or pylon near the water, watching for fish. They are not strongly territorial away from the nest, and where food is plentiful pairs may nest quite close together in loose groups.

Their calls are loud, high-pitched whistles. A pair at the nest keeps up a running conversation of chirps, and alarm calls become rapid and urgent when an intruder comes too close. In spring, males perform a “sky dance”: they climb high over the nest, often carrying a fish or a stick, and then swoop and hover while calling, which advertises the nest site and the male’s fitness.

Bald eagles regularly chase ospreys and force them to drop their catch, then grab the fish in mid-air. This food stealing, called kleptoparasitism, is a common sight along North American coasts and rivers. Ospreys in turn mob eagles, owls and crows that come near their nests.

Nesting and reproduction

Ospreys build large nests of sticks lined with bark, grass, seaweed and moss, usually high up and close to water. Natural sites include dead trees, cliff ledges and rocky islets, but today a great many ospreys nest on human structures such as utility poles, channel markers, cell towers and purpose-built nest platforms. Nests reused for many years can grow to about 2 m (6 ft) across. See where do ospreys nest? for details.

Pairs usually stay together for many years and meet again at the same nest each spring. The female lays two to four eggs, most often three, which are creamy with bold reddish-brown blotches. Incubation lasts about 35–43 days, mainly by the female, while the male brings fish for both of them.

The chicks hatch a few days apart, so the first chick is larger than the last. They make their first flights at about 7–9 weeks old but stay near the nest for several more weeks while the parents keep feeding them. Young ospreys then migrate alone, without their parents, and typically spend their first year or more on the wintering grounds. Most begin to breed at three to five years old.

Lifespan, predators and threats

Many young ospreys die in their first year, especially during their first migration. Adults that survive commonly live 7–10 years, and some live much longer. Ringed wild ospreys have been recorded at about 25 years in North America and nearly 27 years in Europe.

Healthy adult ospreys have few predators. Great horned owls and eagles occasionally kill adults or chicks, and raccoons, crows and other animals may take eggs and young where they can reach the nest. In the southern United States, introduced large snakes such as Burmese pythons are a newer threat to nests.

Human-related dangers are more important today. Ospreys die from electrocution and collisions with power lines, become tangled in discarded fishing line or baling twine woven into their nests, and are sometimes shot illegally on migration. Many young birds die crossing deserts and seas. In Britain, egg collecting, although illegal since 1954 and strictly enforced under the Wildlife and Countryside Act 1981, still threatens some nests, so many nest sites are kept secret.

Conservation status and recovery

The IUCN lists the osprey as Least Concern. It has a huge range and a global population estimated at several hundred thousand birds.

This was not always so. In the 19th and early 20th centuries ospreys were shot as competitors for fish, and egg collectors targeted them. The osprey disappeared as a breeding bird from England in the 1840s and from Scotland by 1916. Then, from the 1950s to the 1970s, the pesticide DDT caused thin-shelled eggs that broke during incubation, and ospreys declined dramatically in parts of North America and Europe, by as much as 90 percent in some areas of the northeastern United States.

The recovery is one of conservation’s success stories. DDT was banned in the United States in 1972 and in many other countries in the 1970s and 1980s. Ospreys quickly accepted artificial nest platforms, and populations rebounded. In Scotland, ospreys from Scandinavia returned on their own in 1954, and the famous nest at Loch Garten has been guarded since 1959. Chicks moved from Scotland to Rutland Water in England helped ospreys breed there from 2001, and today Britain holds roughly 300 pairs.

Myths and facts

• Myth: fish are hypnotized by ospreys. A medieval belief, mentioned by Shakespeare, held that fish turned belly-up in surrender when an osprey flew over. In reality ospreys miss many of their dives.
• Myth: the osprey has one webbed foot and one clawed foot. This old legend has no basis; both feet are the same, with long talons and spiny soles.
• Partly myth: ospreys drown because they cannot let go of large fish. Stories of ospreys dragged under by huge fish circulate widely. A few such incidents have been reported, but they are rare, and ospreys normally release a fish that is too heavy to lift.

Ospreys and people

Few raptors live as close to people as ospreys do. They nest on platforms in marinas, on sports-field lights and on poles beside busy roads, and live nest webcams in the United States and Britain are watched by large audiences every summer.

The osprey is the provincial bird of Nova Scotia in Canada and the state raptor of Oregon, and it appears on many postage stamps. Its old name, sea hawk, inspired the Seattle Seahawks football team. In the UK, ospreys are a flagship of conservation and one of the birds of prey in the UK that visitors most want to see. For a larger fish-eating raptor of North America, compare the osprey with the bald eagle.