Ospreys, carnivorous birds of prey, are superb fishers and indeed eat little else—fish make up some 99 percent of their diet. Because of this appetite, these birds can be found near ponds, rivers, lakes, and coastal waterways around the world. Ospreys hunt by diving to the water’s surface from some 30 to 100 feet (9 to 30 meters) up, hovering over the water until they lunge feet first, dipping their talons into the water to grab their prey. They have gripping pads on their feet to help them pluck fish from the water with their curved claws and carry them for great distances. In flight, ospreys will orient the fish headfirst to ease wind resistance.
Ospreys are sometimes confused with bald eagles, but can be identified by their white under-parts. Their white heads also have a distinctive black eye stripe that goes down the side of their faces. Eagles and ospreys frequent similar habitats and sometimes battle for food. As eagles are larger than osprey, they often force osprey to drop their fish or steal them in midair.
Human habitat is sometimes an aid to the osprey. The birds happily build large stick-and-sod nests on telephone poles, channel markers, and other such locations. Artificial nesting platforms are common in areas where preservationists are working to reestablish the birds. North American osprey populations became endangered in the 1950s due to chemical pollutants such as DDT, which thinned their eggshells and hampered reproduction. Ospreys have rebounded significantly in recent decades, wherever the use of such chemicals is at a minimum. Encroachment of habitat and scarcity of fish are the greatest threats to osprey survival.
Most ospreys are migratory birds that breed in the north, and migrate south for the winter. Ospreys migrate alone, traveling as far as Canada to southern Brazil; or from Scandinavia to Africa. They lay eggs, typically three at a time, generally with the female brooding while the male hunts for both of them, through the 38-day incubation period. Osprey eggs don’t hatch all at once, but are staggered in time so that some siblings are older and more dominant. When food is scarce these stronger birds may take it all and leave their siblings to starve. Although a nestling fledges at around 50 to 55 days, the young depend on their parents to hunt for them for another 8 weeks. Once matured, grown to 23 inches and about 4 pounds with wingspans as long as 6 feet, ospreys are known to live for 30 years.
CEDO Field Station is surrounded by osprey nests, the closest of which is inhabited nearly every year with a brooding pair, was erected by CEDO docents a decade ago. Other nests can be seen on telephone poles in several directions from the Station.