The Osprey, popularly called "Fish Hawk", is one of the most widely distributed birds of prey in the world. It inhabits every continent except Antarctica and is usually found near water. One reason for its success is its highly adapted ability to hunt fish in a manner no other raptor has evolved. Thus it has no direct competitors, and is the lone occupant of an available and productive niche. It is a large raptor with a brown back and white front, a white head and a prominent dark brown eye stripe extending down to the shoulder. It has long, narrow wings, which in flight are bent at the wrists giving them a swept-backed look similar to a gull. Associated with its unique lifestyle, it has evolved a number of unusual adaptations such as a reversible foot and spiny pads for catching and holding fish, and unusual feathers which are water resistant. The Osprey is a top predator in an aquatic food chain and hence is susceptible to biological magnification of certain pesticides. The effects of this accumulation of chemicals in its body was first noticed in the late 1960s when reproductive failure was documented in the Osprey and other raptors. Reproductive failure was the result of egg shell thinning which has been associated with various organochlorines, the most common one being DDT. The banning of DDT and other organochlorines in North America has coincided with an increase in Osprey populations.
SIZE
The Osprey is larger than a buteo yet smaller than eagle. The female is slightly larger than the male. It has a head to tail body length that ranges between 21 and 26 inches (53 to 66 centimetres). Wingspans range between 58 and 70 inches (147 to 178 centimetres). The male averages about 3.2 pounds (1.5 kilograms) and the female averages about 3.9 pounds (1.8 kilograms).
MORPHS
There is very little individual variation in plumage. Juveniles obtain adult plumage after about 18 months, once the distal ends of the feathers have worn away. Other than streaking on the breast, which is sometimes distinguishable on the female, the plumages of the sexes are almost alike.
SPECIFIC DESCRIPTION
Adult Male - Perched
- prominent white head with speckled crown
- brown back and white underparts
- dark brown eye stripe extends to shoulder
- bright yellow eye
- feathering half way down leg
- short tail without terminal band
- underparts white
Adult Female - Perched
- slightly larger body size than male
- similar to male plumage but has light to dark brown streaks or splotches which contrast with white underparts to form a necklace across breast. It should be noted that this plumage trait may not always be present on every inividual.
Immature - Perched
- back is predominantly brown but white to pale edges to the feathers give it a "scaly" appearance
- head is streaked brown and white
- red to orange eye
- white band on tip of tail
SIMILAR SPECIES
The Osprey's large size, white head, and similar habitats will sometimes suggest an adult Bald Eagle. However, a closer look at the diagnostic differences in size, wing shape, eye line, and banded tail will allay any confusion. When soaring at a distance the Osprey looks similar to larger gulls, primarily because of the crooked narrow wings and the predominantly white underside. Gulls have unbanded tails, and lack black wrist patches on the underside of the wings.
OTHER NAMES
The Osprey is often locally known as "Fish Hawk" or "Fish Eagle."
ETYMOLOGY
Osprey is derived from the Latin ossifraga meaning "bone-breaker." The Genus Pandion is taken from the name of a mythical King of Athens who, along with his two daughters, were transformed into birds. The species name haliaeetus is Greek for "salt or sea eagle" an allusion to the eagle that hunts in the sea. In coastal areas the Osprey does forage for perch in the ocean.
MYTHOLOGY
The Osprey is revered for its hunting skills by Bolivian Indians. In one documented case, an Osprey was shot with a bow and arrow, where upon a bone was taken from the hawk and slipped under the skin of the hunter in order to "absorb" hawk-like hunting skills.
VOICE
The Osprey has an ascending high pitched plaintive call which rises in quarter tone "chewk-chewk-chewk", with the last notes somewhat slurred. The male has the deeper call. When circling above the nest, either alone or together in a sky dance, it will call "cree-cree-cree" repetitively for up to 15 minutes. Females elicit a softer, more muted call issued in single notes when the male approaches the nest with nest material or prey items.
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