The osprey (Pandion haliaetus) is a large, majestic bird of prey, with a 3-foot wingspan, dark brown back, white or slightly mottled underparts, and a white head with a dark eye stripe.
The time to see ospreys in Rhode Island is April through August-the birds use southern New England as their breeding grounds. Large concentrations of nesting ospreys can be found at the Great Swamp Management Area, South Kingstown, and at Napatree Point in Westerly. Migrants continue to be seen in the area into fall.
Ospreys feed almost exclusively on live fish. Their feet have short, sharp spines that cover the foot pads and toes for holding their prey, and the talons are long and razor sharp. The legs are long and without feathers, allowing the birds to extend their reach under water. When hunting, ospreys usually hover over the water until they spot their prey, then plunge, feet first, into the water to grab it.
Breeding and Nesting
Ospreys are monogamous and often return to the same nest site year after year. The birds can be seen nesting in trees, on telephone poles, on channel markers, or on specially constructed platforms. Once they arrive at the breeding grounds, males search for a suitable nest site and begin to perform their courtship aerial display above the nest siteoften called the "fish-flight" or "sky dance"to attract a mate. Once a pair has settled at a nest site, the female gives begging calls to her mate to bring food. During "courtship feeding," females are fed almost exclusively by their mates, doing almost no hunting on their own.
Both male and female share incubation duties, although the male continues to bring food to his mate, and later to the brood. By 30 days old, the young have attained 70 to 80 percent of their adult weight.
Osprey populations were decimated between 1950 and 1975 due to the effects of the pesticide DDT, which made its way up through the food chain to the birds, often thinning eggshells and poisoning or killing some embryos, so that few eggs hatched. During that period, 90 percent of ospreys nesting between Boston and New York City disappeared. A ban on DDT in 1972, combined with construction of special platforms to provide the recovering population with nesting sites, has resulted in a remarkable comeback. The platforms helped the birds to overcome two hindrances to survivala decrease in natural nesting sites due to development, and an increase in nest predators, in particular, the raccoon. Nesting distribution is now roughly similar to that seen historically. Osprey may be seen nesting on platforms at the Osamequin Bird Sanctuary in Barrington, and in other wildlife refuges throughout the state.
This article first appeared in A Guide to Rhode Island's Natural Places, produced by Rhode Island Sea Grant.
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