Osprey

Pandion haliaetus

Habitat: Seashore, coastal marshes, lakes and rivers.
Weight: Males, 2 to 3.5 pounds; females, 2.75 to 4.25 pounds.
Length: 21 to 25 inches; wingspan: 54 to 72 inches.
Food: Almost entirely fish.

Identification: The osprey is a large hawk distinguished in flight by its white underparts and the distinctive crook formed by its long, narrow wings. Adults are brown to brownish-black above with brownish-black marks on the wings and buff to brown speckling on the breast. The head is white with a dark crown and there is a wide, dark brown stripe extending through the eye down the cheek. Both sexes are similar in appearance, although the female is larger. Full adult plumage is achieved at 18 months. Juvenile osprey strongly resemble the adults, except that the brown feathers of the upper body are tipped buff-white, and the streaking on the breast and crown tends to be heavier. The eye color changes from brown to yellow as juveniles mature.

Range: The osprey is found almost worldwide. Its nesting range in North America includes coastal areas and large inland lakes. These birds then overwinter from Florida to northern coastal Mexico and south to northern South America.

Reproduction: Osprey return to Connecticut from their southern wintering grounds in late March. They usually choose nest sites near or over water but will travel up to several miles from the nest to seek food. Preferred natural nest sites are the tops of dead trees (snags). However, osprey adapt to available sites and have been known to nest on top of duck blinds, channel markers, roots of upturned trees, chimneys, school buildings and utility poles. Osprey readily use artificial nest platforms, and wildlife managers encourage the use of such platforms in areas where there are few natural nest sites. Osprey do not confine themselves to sticks when building their large nests; seaweed, bones, driftwood, cornstalks and trash from nearby beaches and marshes may also be included.

Osprey pairs usually return to the same nest site and add new nest materials to the old nest each year. An average of three eggs is laid in April; incubation begins with the first egg laid. Eggs are white to pink or cinnamon and heavily blotched with dark brown. Adults are protective of the nest site and may exhibit aggressive behavior at the approach of a potential intruder. The month-long incubation period is usually completed by the female, who is fed by the male during this time. Sixty days after hatching, young osprey make their first flight. After fledging, the young remain with the parents for up to two months. Young remain at wintering grounds for two to three years until they return to the north to make their first breeding attempt.

History in Connecticut: In the 1940s, the coastal zone between New York City and Boston supported an estimated 1,000 active osprey nests. However, development pressures and eggshell thinning caused by DDT contamination reduced this number to 150 nests by 1969. The banning of DDT in the 1970s and restrictions on the use of other organochlorine pesticides have prompted a steady recovery of osprey populations.

In Connecticut, the osprey population has experienced a steady increase since 1974, when there was an all-time low of nine active nests. Once again, it is not unusual to see osprey along Connecticut's coast and rivers. While the numbers are cause for optimism, osprey are still exposed to pesticide contamination at their wintering grounds in the West Indies, Central America and northern South America. Therefore, careful monitoring of the osprey population continues to be important.

Interesting Facts: The osprey is known as the "fish hawk" and feeds almost exclusively on fresh fish. It can capture a fish weighing up to four pounds. The toes of the osprey reflect a unique adaptation to its feeding habits; the lower surface of the toes is covered with spicules (short, spikelike protrusions) which guarantee a firm grip on any fish caught. In addition, osprey, like owls, have a reversible outer toe, enabling them to grasp their prey with two toes in back and two toes in front. The osprey's plumage is compact, an attribute which helps blunt the impact and reduces wetting when it plunges into the water while fishing. After prey is captured, it is carried headfirst in flight to reduce air resistance.

The development of the shore for recreation has reduced the number of available osprey nest sites. Human activities encourage the presence of predators, such as raccoons, that climb into the nests and destroy the eggs or young. One of the most detrimental human activities is littering. Carelessly discarded litter along the shoreline, especially plastic six-pack yokes and monofilament fishing line, which are often used as nest material, can cause the strangulation death of young osprey. People are encouraged to dispose of all litter in an appropriate, safe manner. Human disturbances also affect nesting success by keeping adults off the nest, thus preventing them from attending young. During the nesting season, people or their pets should maintain a distance of at least 500 feet from an osprey nest. Disturbance of ospreys is prohibited under the Federal Migratory Bird Treaty Act of 1918 and the Connecticut General Statutes Section 26-92.

The Wildlife Division surveys all active osprey nests during the summer; volunteers are always welcome to help in the effort. Contact the DEEP Office of Long Island Sound Programs for a free permit application if you are interested in erecting an osprey nesting platform in a tidal wetland on your property.

The Technical Assistance Informational Series is 75 percent funded by Federal Aid to Wildlife Restoration - Pittman-Robertson (P-R) Program. The P-R Program provides funding through an excise tax on the sale of sporting firearms, ammunition, and archery equipment. The remaining 25 percent of the funding is matched by the Connecticut Wildlife Division. (rev. 12/99)