How to Recognize an Osprey
Ospreys (Pandion haliaetus), sometimes called fish hawks, are
fish-eating
birds of prey midway in sized between large hawks and eagles. They are mainly
white when viewed from below, with dark speckles on the breast, barring on wings
and tail, and a dark patch at the bend of the wing. Above they are dark brown.
They have a dark eye-line, or mask, on a white head. Eyes are vivid yellow.
Immature are like adults except that their upper parts are flecked with white.
In flight, an Osprey's wings have a conspicuous bend or arch, reminiscent of a gull's. Wings are long in proportion to the body size and wing beats are typically slow and deep. Ospreys emit a loud, clear whistle - often in a series and sometimes in response to other ospreys.
Expert Fishers
As members of the predatory order that contains hawks, eagles and falcons, ospreys posses the characteristic hooked beak for tearing flesh and sharp claws for seizing prey. Ospreys eat almost exclusively fish that they have caught. Carp, catfish, perch, shad and suckers have been reported in their diet. On extremely rare occasions they have been seen catching snakes, frogs and even shorebirds.
A hunting osprey usually flies back and forth over, and 50 to 200 feet above, a body of water while attempting to sight a fish on the surface. When it spies a fish, the osprey hovers in place before diving and plunging into the water feet first. Often it will completely submerge except for the wings.
- Length: 2 feet
- Wingspan: 5 to 6 feet
- Weight: 3 to 4 pounds
Once the grasp is secured, the osprey carries its catch to a perch or nest site. In flight the fish is carried head-first so that it offers less wind resistance. The osprey typically performs a wiggle in flight to shake water from its feathers. Observations have indicated that ospreys are 80 percent effective at catching a fish when they make a dive. They reportedly are able to carry fish that weigh up to four pounds. Small spikes on the bottoms of their toes enable them to hold slippery fish.
Universal Residents
Ospreys are one of few bird species that are nearly worldwide in distribution. In North America they breed along both the East and West coasts and inland through the Great Lake states, the northern Rockies, across Canada and throughout much of Alaska. They breed in association with seacoasts, lakes and rivers, and usually select the tops of tall trees for their large, stick nests. Occasionally they will nest on artificial structures, including towers, channel markers and idle Ferris wheels.
When migrating between their breeding range and their South American wintering range, ospreys can be sighted throughout most of the United States. In Missouri, ospreys migrate from mid-march to mid-May in spring and during September and early october in fall. They are sighted along rivers, on lakeshores and even over farm ponds.
Nest Recyclers
The birds become sexually mature at three years old, and can live 15-20 years in the wild. Pairing occurs in early spring and commences with nest construction. Previously used nests are expanded each year, and therefore, can become immense structures of three feet across and several feet deep. Although each pair is territorial, several pairs will often nest in a loose colony with each nest in view of another.
A clutch of consists of two to four splotched eggs approximately the size of a turkey's. Egg laying occurs from late April to early may in Minnesota. The eggs hatch in about 3 days. Another eight to nine weeks is required for the young to achieve nearly adult size and fly form the nest. In Minnesota, fledgling usually occurs in mid to late July.
A Little History
Ospreys were formerly numerous throughout North America, but diminished significantly in numbers during the 1950s and '60s in response to pesticide contamination of the fish that they consume. Since the banning of DDT in 1972, they have rebounded significantly. In portions of Minnesota and Wisconsin they are nearly four times as numerous as during the 1970s.
Ospreys are known to have formerly bred in Missouri; however, they were apparently never plentiful, and they disappeared as breeders well before the DDT era. They nested in the swamplands of the southeast and along the Gasconade, Osage, Missouri and Mississippi rivers. Osprey habitat, in the form of reservoirs, is probably more prevalent in Missouri today than it was in the past.
Restoration in Missouri
Because ospreys tend to nest near where they first fly, the restoration of breeding ospreys to Missouri can be accomplished by bringing nestling ospreys to Missouri and releasing them from artificial nests. These artificial nests are called "hacksites," and the process of releasing them is called "hacking" - terms derived from the sport of falconry.
Osprey restoration began in Missouri in 1995. Various favorable release sites throughout Missouri have been used with four to eight chicks released at each site each year. Cooperators of the project include the U.S. Army Corps of Engineers and Kansas City Power and Light, which has paid for the acquisition of young osprey.
Nestling ospreys are placed in boxes on a tower of 8- 12-foot scaffolding, with an electric predator-proof fence around the foot of the tower to deter predators. Towers are set up with a 360 degree visibility, usually near a wetland or lake.
Six-week-old chicks are received in July from Minnesota and fed fresh fish daily until they are 8- to 10-weeks old. This allows the ospreys to imprint on, or learn about, their new home. The hack boxes are designed to open on one side when the chicks are mature enough to begin flying.
Newly released birds are identified by leg bands and a paint patch on one of their upper wings near the shoulder. This paint enables hacksite personnel to keep track of chicks, is not harmful and wears off in the fall. These birds can be identified throughout their lives by an aluminum band on one leg and a colored plastic band on the other.
Success
The first confirmation of released ospreys returning to Missouri to breed was in 2000. As more of the released ospreys attain reproductive age, and as nesting birds add their progeny to the population, their numbers should continue to increase.
If you see an osprey on a nest, please report it immediately to: Natural History Division, Missouri Department of Conservation, P.O. Box 180, Jefferson City, MO 65102-0180, 573-751-4115.
