Ospreys, Pandion haliaeetus, commonly called fish hawks or fish eagles, are neither a true hawk nor eagle. The species is of ancient lineage and is presently classified near the, hawk-like, kite family (Accipitridae.) “Osprey” came from Latin “ossifragus”, meaning “bone breaker,” but this name probably referred originally to another species. Pandion was the name of two mythical kings of Athens: “haliaeetus” is from the Greek “hals” and “aetos", meaning “sea” and “eagle.”

Ospreys have worldwide range, and four subspecies are presently recognized. Two subspecies occupy North America P.h. carolinensus in temperate North America (includes Iowa) and P.h. ridgwayi in the Caribbean.

These birds of prey are large narrow-winged, fishing raptors, weighing 2.2 to 4.2 pounds. Length is 21 to 26 inches and wingspread is 59 to 67 inches.

Sexes are similar in appearance, but females tend to be 10% larger than males. Also, coloration on females includes pronounced dark flecking or “necklace” on their chests. Eyes are red/orange in immature birds and yellow in adults. A distinctive blackish-brown stripe extends across the eye and down the side of the neck..

Other field mark characteristics include wing linings that are white with dark barring, and dark carpal patches at wrist regions that are conspicuous when viewed from below. Typical flight has wings angled back much like sea gulls Osprey calls consist of a series of shrill, staccato whistles, gradually rising in pitch, tewp, tewp, teelee, teelee, tewp.

Ospreys are superb at fishing, catching prey with their feet after spectacular feet-first dives. They usually enter the water completely. Although they are almost exclusively fish-eaters, their diet has been reported to include a few other prey items, such as birds, turtles and small mammals.

Growth and Development

• Courtship flights by males are a series of undulating dives and climbs, usually performed while the bird is carrying a fish and calling constantly.
  
  
• Nests sites are usually in the top of dead trees, but nests are also placed on man-made structures such as duck blinds, channel markers, and navigation aids and telephone poles. Ground nests occur, most frequently on islands.
  
  
• Osprey clutches consist of three or four eggs that are creamy white and heavily spotted brown. Eggs are laid at two-to-three-day intervals in May. After the first egg is laid, incubation proceeds 30 days and is dominated by the female.
  
  
• The male provides food for the female and brood after hatching. The female remains in constant attendance the first 30 days providing protection from predators and the elements.
  
  
• At 42 days, young can tear apart fish provided by parents and around 53 days, first flight occurs.
  
  
• Young of the year quickly acquire fishing skills and gradually expand their range until dispersal in late August. Immature ospreys spend up to 20 months at their over-wintering areas in Central and South America.
  
  
• Adults attain sexual maturity when three or four years of age. Average life expectancy is ten years.

Notable Features

• Ospreys’ pale bluish talons are tipped with nature’s finest fishhooks: claws, sharp as needles. Their outer toes, like those of owls, are reversible; this character and the sharp protuberances or “spicules” on the lower surface of the toes allow them to grasp slippery fish.
  
  
• Osprey wing joints are specialized to withstand 40-50 mph dives into water by “double jointing” up ward, then able to lift bird vertically from the water.
  
  
• According to much folklore, Bald Eagles rob Ospreys of fish, but they do so rarely in real life. The two species cohabit water areas surprisingly peacefully, with only an occasional conflict, initiated by either species.
  
  
• Male Ospreys show strong fidelity to ancestral breeding areas, preferring to nest colonially where adults originated. Females may disperse hundreds of miles from their origin to nest, however males will generally return within 20 miles of origin.
  
  
• Due to this very low dispersal tendency by males, young Ospreys are prime candidates for relocation. Projects are designed to spread young, geographically, to areas where Ospreys do not nest. This strategy will ultimately improve nestling survival and complete historic continental population distribution.