Field Guide/Birds/Pandion haliaetus

The Osprey (Pandion haliaetus) is a medium large raptor which is a specialist fish-eater with a worldwide distribution. It is often known by other colloquial names such as fishhawk, seahawk or Fish Eagle. It is the only living species of the genus Pandion, which is in turn the only genus in family Pandionidae.

The Osprey is 52-60cm (20.5-23.6 inches) long with a 152-167cm (5-5.5 feet) wingspan. It has white underparts and long, narrow wings with four "finger" feathers at the end of each, which give it a very distinctive appearance.

Their call is a series of sharp whistles, cheep, cheep, or yewk, yewk. Near the nest, a frenzied cheereek!

The Osprey differs in several respects from the other diurnal birds of prey, and has always presented something of a riddle to taxonomists. Here it is treated as the sole member of the family Pandionidae, and the family listed in its traditional place as part of the order Falconiformes. Other schemes place it alongside the hawks and eagles in the family Accipitridae—which itself can be regarded as making up the bulk of the order Accipitriformes or else be lumped with the Falconidae into Falconiformes. The Sibley-Ahlquist taxonomy has placed it together with the other diurnal raptors in a greatly enlarged Ciconiiformes, but this has more recently turned out to result in an unnatural, paraphyletic classification.

Ospreys are peculiar insofar as that a single species occurs nearly worldwide. Even the few subspecies are not unequivocally separable. The reason is apparently that these birds are usually migratory, enabling individuals from populations which breed far apart to meet in the winter quarters, form pairs and thus exchange genetic information between populations. Furthermore, ospreys are long-lived birds which take a considerable time to reach maturity, which does slow down the rate of speciation. However, there were several prehistoric species of osprey which have been described from fossils:

• Pandion sp. (Early Oligocene of Fayyum, Egypt)
• Pandion homalopteron (Middle Miocene of California, USA)
• Pandion lovensis (Late Miocene of Florida, USA)
• Pandion sp. (Late Miocene/Early Pliocene of Lee Creek Mine, USA)

P. homalopteron was very similar to the living species and possibly even its direct ancestor. However, the biogeography of the fossil ospreys has not been researched well enough to suggest a place where the modern osprey originated. The genus apparently first appeared in the Mediterranean region, but this is not certain.

The Australasian Osprey is the most distinctive subspecies.

The Osprey is particularly well adapted to its 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 catch fish. It 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, where it may either swim to safety or succumb to hypothermia and drown.

It breeds by freshwater lakes, and sometimes on coastal brackish waters. The nest is a large heap of sticks built in trees, rocky outcrops, telephone poles or artificial platforms. In some regions with high Osprey densities, such as Chesapeake Bay, USA, most Ospreys do not start breeding until they are five to seven years old. Many of the structures they need to build nests on are already taken. 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.

Ospreys usually mate for life. In March or earlier depending on region, they begin a five-month period of partnership to raise their young. Females lay 3–4 eggs by late April, and rely on the size of their nest to help conserve heat. The eggs are approximately the size of chicken eggs, and cinnamon colored. The eggs generally incubate for 5 weeks. After hatching, 2-ounce chicks become fliers within eight weeks. When food is scarce, the first chicks to hatch are most likely to survive. The typical lifespan is 20-25 years.

European breeders winter in Africa. American and Canadian breeders winter in South America, although some stay in the southernmost USA states such as Florida and California. Australasian Ospreys tend not to migrate.

Twenty to thirty years ago, Ospreys in some regions faced possible extinction, because the species could not produce enough young to maintain the population. Since the ban of DDT in many countries in the early 1970s, together with reduced persecution, the Ospreys, as well as other affected bird of prey species are making significant recoveries.

The Osprey is the official bird of Nova Scotia in Canada and Sudermannia in Sweden. The osprey is often maligned by officials in the National Football League. It is the official mascot and team name for the University of North Florida and the Richard Stockton College of New Jersey. The bird was depicted on the 1986 series Canadian $10 note. The Osprey is also the mascot of the Christian Falangist Party of America

See also

• Ospreys in Britain
• Australian Osprey (photo)

References

• Template:IUCN2006 Database entry includes justification for why this species is of least concern

External links

• RSPB UK Osprey Diary with links to much other bird information
• For numerous links to information about ospreys in Britain.
• A little about ospreys in West Virginia
• Osprey videos on the Internet Bird Collection
• Live Web cam on an osprey nest (located on Lake Washington at Kennydale, Washington)