Wild Florida: Osprey

The Osprey, also known as the Fish Hawk and sometimes as the Sea Hawk, is one of the most widely-distributed birds of prey in the world, found on every continent except Antarctica. In Florida, it is a year-round resident, and often shares its habitat with the much-larger Bald Eagle.

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Osprey

The Osprey, Pandion haliaetus, stands about two feet in height and has a wingspan of about 6 feet. It is strikingly colored in brown, black and white, and the bold dark stripe on the side of the face is a distinguishing marker. Females usually have a darker patch across the upper chest, and are slightly larger in size. The call is a high-pitched repeated chirp, seemingly unbefitting for such a large raptor. Osprey are adaptable birds, found virtually anywhere where they can find a body of water as a source of fish for food. They are commonly found in urban areas such as parks.

As the common name “Fish Hawk” suggests, they feed almost exclusively on fish, both freshwater and saltwater. They can often be seen circling slowly above a body of water, looking for fish near the surface which they then swoop down upon, diving into the water feet-first to make the catch.

Osprey have several anatomical and behavioral adaptations which help them in their fishing. Unlike most raptors, Osprey have four toes of equal length, with a reversible rear toe and very strong talons. The skin on the inside of the toes has extra-large rough scales. All of these help the bird grasp and carry slippery fish. The Osprey has extra-oily feathers to prevent them from getting wet, and closable valves in its nostrils to keep water out during a dive. The eyes are also adjusted for accurately seeing fish even through the refraction of water. After a catch, the Osprey will manipulate the fish in flight so its head faces front to make it more aerodynamic and easier to carry. Fish make up almost all of the diet, supplemented with an occasional small mammal or bird.

Because of its unique adaptations, the Osprey has been placed into a separate taxonomic family, the Pandionidae. There are four subspecies of Pandion haliaetus, found worldwide. P.h. haliaetusis the most widespread, found in Europe, Asia and Africa. In North and South America, the subspecies is P.h. carolinensis, with another subspecies, P.h. ridgwayi, found in the Caribbean Islands. In Australia, the subspecies is P.h. cristatus, though some taxonomists are now classifying this as its own separate species, Pandion cristatus.

Most of these are migrants, spending the winter months in warmer areas and then migrating to more temperate climates in the summer. In Europe the bird migrates as far north as Scandinavia; in North America it is found in Canada and Alaska. Migrating Osprey can travel enormous distances: one bird, fitted with a radio collar, was measured to have flown from Massachusetts to French Guiana, a distance of 2700 miles, in just 13 days. European Osprey migrate to Africa. The Caribbean and Australian populations, however, don’t migrate and stay year-round in the same areas.

In Florida, the carolinensis subspecies can be found both as a migrant and as a permanent year-round resident. Although the ridgwayi subspecies is not native to Florida, it occasionally turns up as an errant, blown here accidentally by a storm or hurricane.

Fossil relatives of the Osprey have been found in Florida, California, Egypt and Germany.

Osprey can live comfortably in urban areas in close proximity to humans. They can survive any place where there is a nearby source of fish–freshwater or saltwater. They prefer shallow waters where the fish school near the surface. In southern parts of the US, Osprey will often nest in large trees, or atop light poles in parking lots or streetlights and telephone poles. In many areas, man-made nesting platforms are put up for the birds. The nests are large piles of sticks, lined with grass or bark. Breeding pairs return to the same nest year after year, enlarging it each time.

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Osprey nest atop a light pole.

Young Osprey are ready to mate at about age three. The young male selects a suitable nesting site, then flies around it carrying a fish or nesting material to entice a female to mate. Once established, mating pairs stay bonded for life. In migratory pairs, the male and female arrive back at the nest separately, with the male usually appearing first. The eggs are laid in spring, with 3 or 4 eggs laid a few days apart. These hatch in about 35 days. The hatchlings require 3-8 fish per day, delivered by the parents. In good years, all of the chicks may get enough food to fledge, but in poorer years only the largest and strongest will survive. The young birds leave the nest at about six weeks, but will hang around their parents for another few months until they are strong enough to survive on their own. Osprey may live as long as 20 years.

In the 1950’s, Osprey populations throughout the US began to crash, with some areas losing over 90% of their resident birds. The problem was the insecticide DDT, which was sprayed on crops, washed into the water where it was concentrated in fish and eaten by the birds, where it produced unusually thin eggshells that prevented the Osprey from breeding. In some areas, the problem was exacerbated by the loss of trees as nesting sites. In 1972, DDT was banned in the United States. Combined with a program of providing artificial platforms as nesting sites, this led to a rebound in populations. Today, although it is still listed as “threatened” in some areas, the Osprey has made a comeback and is no longer considered to be endangered.

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