The Osprey (Pandion haliaetus) is a fish-eating hawk found along coastlines and around marshes, lakes, and rivers almost worldwide. Ospreys are often seen flying over water searching for prey, then hovering and plunging feet first to capture a fish in their talons (fish are normally carried head first and belly down). Bald Eagles may sometimes chase them and force them to drop their catch. During migration, Ospreys may be seen far from water, even over deserts. Migrants travel singly, not in flocks.
The Osprey's diet consists almost entirely of fish, generally in the range of 10 to 30 cm in length. Rarely, small mammals, birds, or reptiles may be eaten.
Ospreys breed in the New World over most of North America south to Guatemala; in the Old World, they breed from the British Isles, Scandinavia, northern Russia, and northern Siberia south (at least locally) through much of Eurasia and most of Africa and Australia to South Africa, the Himalayas, Tasmania, New Caledonia, and the Solomon Islands. They winter from the southern United States south through Middle America, the West Indies, and South America (including the Galapagos Islands) to southern Chile, northern Argentina, and Uruguay; in the Old World, Ospreys winter from the Mediterranean, Black, and Caspian Seas, India, and eastern China south through the remainder of the breeding range.
The Osprey's courtship display includes the pair circling high together; the male may fly high and then dive repeatedly in the vicinity of the nest site, often carrying a fish or stick. The nest is usually constructed at the top of a large tree (often with a dead or broken top) not far from water. Utility poles or other structures, including nesting platforms erected by humans expressly for Ospreys, may also be used. They may nest on the ground on small islands and on cliffs or giant cacti in western Mexico. The nest site is typically very open to the sky. The bulky nest, built by both sexes, is made of sticks and lined with smaller materials. Nests may be reused for many years, with material added each year. Typical clutch size is 3 (range 2 to 4). The eggs, which are creamy white with brown blotches, are incubated by both parents (but mainly the female) for around 38 days. When the young first hatch, the female remains with them most of the time, sheltering them from sun and rain, and the male brings fish back to the nest, which the female feeds the young. Age at first flight is around 51 to 54 days.
In the mid-20th century, Osprey populations in the United States and elsewhere plummeted as a result of accumulations of the pesticide DDT in the food chain, which prevented the formation of normal eggshells (DDT can interfere with normal calcium absorption, resulting in thin eggshells). With the reduction in use of DDT and other conservation efforts, populations of Ospreys and some other affected species have rebounded.
(Kaufman 1996; AOU 1998; Dunn and Alderfer 2011)
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