The Osprey bird (Pandion haliaetus) is a medium-large raptor which is a specialist fish-eater with a worldwide distribution. It occurs in all continents around the world except for Antarctica, but in South America only as a non-breeding migrant. The Osprey bird is often known by other colloquial names such as ‘fishhawk’, ‘seahawk’ or ‘Fish Eagle’.
Because the Osprey bird is a species with many unique characteristics it has therefore been given its own taxonomic genus, Pandion, and family, Pandionidae.
Ospreys are remarkable hunters, having adapted their hunting style to match their environment – they can be seen hovering over water, then diving feet-first to snatch their prey out of the water.
Osprey Bird Characteristics
The Osprey weighs around 1400 – 2000 grams (3 – 4.4 pounds) on average, and has a length of 52 – 60 centimetres (20.5 – 24 inches). It has a 150 – 180 centimetres (5 – 5.9 feet) wingspan. The Osprey has mainly white underparts and head, apart from a dark mask through the eye, and fairly uniformly brown upperparts. Its short tail and long, narrow wings with four long ‘finger’ feathers (and a shorter fifth) give it a very distinctive appearance.
In flight, Ospreys have arched wings and drooping ‘hands’, giving them a gull-like appearance. Their call is a series of sharp whistles, cheep cheep, or yewk yewk. When Ospreys are near their nests, they vocal a frenzied ‘cheereek’.
Location & Habitat
Ospreys generally prefer to live near large bodies of water such as oceans, lakes, and rivers, where they have plenty of opportunities to hunt for fish. They typically build their nest in the highest trees or man-made structures that are available near the water, such as tall telephone poles or bridge beams. In addition to coastal areas, ospreys can also be found in inland wetlands and estuaries.
They are also common near fish farms and other artificial bodies of water where large numbers of fish are present. Ospreys have even been known to nest on oil rigs out at sea! Throughout their range, ospreys are reasonably tolerant of human activity.
Diet
Their diet predominantly consists of fish that they capture in shallow waters. They are able to spot their prey from a long distance and then plunge headfirst into the water with their talons extended so they can grab hold of the fish. Fish they capture are generally 150 – 300 grams (5.3 – 10 oz) and measure about 25 – 35 centimetres (10 – 12 inches) in length.
The Osprey is particularly well adapted to this diet, with reversible outer 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.
The Osprey locates its prey from the air, often hovering prior to plunging feet-first into the water to seize a fish. As it rises back into flight the fish is turned head forward to reduce drag. The ‘barbed’ talons are such effective tools for grasping fish that, on occasion, an Osprey may be unable to release a fish that is heavier than expected. This can cause the Osprey to be pulled into the water. Rarely, Ospreys may prey on other wetland animals, such as reptiles (up to the size of young alligators), aquatic rodents, salamanders and other birds.
Reproduction
The Osprey breeds by freshwater lakes and sometimes on coastal brackish waters. Most Ospreys do not start breeding until they are five to seven years old. If there are no nesting sites available, young Ospreys may be forced to delay breeding. To ease this problem, posts may be erected to provide more sites suitable for nest building.
Osprey usually mate for life. In spring they begin a five-month period of partnership to raise their young. They form strong pair-bonds with their mates during breeding season. Female Osprey lay 3 – 4 eggs within a month and rely on the size of the nest to help conserve heat. The cinnamon-colored eggs weigh about 65 grams (2.4oz). The eggs are incubated for about 5 weeks before they hatch.
The newly-hatched Osprey chicks weigh only 50 – 60 grams (2oz), but fledge within eight weeks. When food is scarce, the first chicks to hatch are most likely to survive.
Juvenile Osprey are identified by the buff fringes to the upper-part plumage, buff tone to the underparts and streaked crown. By spring, wear on the upperparts makes barring on the underwings and flight feathers a better indicator of young birds. Adult male Ospreys can be distinguished from female Osprey from their slimmer bodies and narrower wings. They also have a weaker or non-existent breast band than the female and more uniformly pale underwing coverts. The typical life span of the Osprey is 20 – 25 years.
Predators
Bubo owls, great horned owls and Bald Eagles (and possibly other eagles of comparable size) are the only major predators of juveniles and adults. Ospreys have rarely been known to be preyed on by crocodiles when they dive into the water.
Young chicks and eggs may be more vulnerable in the nest however, with specific predators varying depending on the range and habitat. Those opportunistic predators only too happy to raid a nest include crows or other corvids, pine martens and raccoons.
Threats & Conservation
Twenty to thirty years ago, Ospreys in some regions faced possible extinction, because the species could not produce enough young to maintain the population. Possibly because of the banning of DDT (Dichloro-Diphenyl-Trichloroethane) and other dangerous pesticides in many countries in the early 1970’s, together with reduced persecution, the Ospreys, as well as other affected bird of prey species have made significant recoveries.
While populations have increased in North America and Europe, in Africa the numbers continue to decline and in some regions have become locally extinct.
As of 2007, Ospreys have been listed as a species of ‘Least Concern’ on the IUCN Red List.
Osprey Bird Quick Facts
- Some nesting sites are known to be generational, with Osprey reusing them year after year. This is most common when a particular site has been successful. They are likely to move on from unsuccessful nests
- An Ospreys normal flight speed is around 50 km/h, increasing to 125 km/h in steep hunting dives.
- Depending on where they live, Osprey are know to be both migratory or non migratory birds.
- Ospreys are well designed for their aquatic diet, with reversible outer toes for catching fish, and closable nostrils for keeping water out.
- Ospreys are Carnivores, and fish make up the vast majority of their diet. However in some inland areas of Africa where fish are rare, they have also been known to eat small mammals, reptiles and invertebrates. They may even snag a water bird if they are hungry enough.
- In areas like the UK where they eat only fish, they are able to coexist with other birds of prey, as neither are a threat or competitor to each others food supply.
- Raccoons Pine Martens are notorious opportunistic predators known to steal osprey eggs straight from the nest.
- The Osprey’s talons are more like that of an owl than that of a hawk.
- The Osprey species has been around for a very long time, with fossil evidence going back between 11-13 million years!
- Ospreys are monogamous and have elaborate mating rituals
- Ospreys that breed in the UK, all migrate south to winter in Africa when the breeding season is over. Those that do migrate, do so over very long distances!
