The warmer temperatures have brought with them a familiar Chesapeake icon. Ospreys (Pandion haliaetus) occur in nearly every corner of the globe, but nowhere as abundantly as on the Chesapeake Bay.
Ospreys return to the Chesapeake every spring from southern wintering grounds. Their abundance in the Bay region is due to the availability of food: They feed exclusively on live fish.
Their curved, sharp talons and rough-soled feet are designed to hold on to slippery fish.
Large brown and white birds of prey, they're about 2 feet long with wing spans of 4-5 feet. When in flight, their long, narrow wings take on the shape of an outstretched M.
Ospreys hunt by soaring over water, periodically hovering on beating wings to scan the surface for schooling or spawning fish. Upon sight of its prey, the osprey makes a spectacular dive. Folding its wings tightly, it descends swiftly and plunges feet first into the water, often submerging itself completely. Another technique is a shallow scoop for fish at the water's surface.
In addition to food, the Chesapeake provides many favorable nesting areas over the water such as duck blinds, navigation markers or man-made nesting platforms. Offshore structures offer protection from predators like raccoons, and rapid detection and escape from danger. On land, ospreys may nest on high trees and utility poles.
Ospreys 3 years or older usually mate for life, and will use the same nest site year after year A recently reunited pair will begin the task of nest building or repair.
Younger birds must first attract and court a mate. During courtship, the male will feed the female and it is believed that this may actually strengthen the pair's bond to one another. Spring courtship marks the beginning of a five-month period when the pair works together to build a nest and raise their young.
A clutch of three or four eggs is laid by the third week of April. The sheer bulk of the nest and a depressed center conserves heat. The eggs, usually mottled cinnamon brown, are about the size of jumbo chicken eggs, and must be incubated for nearly five weeks.
Finally, the eggs yield their treasures: helpless chicks, weighing 2 ounces or less, that can barely beg for food. Amazingly, with plenty of fish, these balls of fluff will become soaring acrobats in just eight weeks.
By late July, most young Chesapeake ospreys are on the wing. By the end of August, both young and adults begin their southern migration to wintering grounds in the Caribbean, Central America and South America.
Ospreys, swooping and plunging for fish, have always been a familiar site for residents and workers on the Bay. But there was a time, not long ago, when the osprey's survival on the Chesapeake was threatened.
For years, ospreys and many other birds of prey were unable to produce enough young to maintain their populations. Production decreased because of egg failures caused by extremely thin and easily broken eggshells.
Years of research led to the discovery that a pesticide, known as DDT, caused eggshell thinning in many birds. Since World War II, DDT was sprayed to control mosquitoes and crop pests. The use of DDT was banned in the United States in the early 1970s. Osprey and other birds of prey have since made remarkable recoveries.
Despite the hardships, ospreys have continued to flourish around the Bay. Their spectacular flights and insistent calls can be heard throughout the spring and summer. The resurgence of ospreys after the ban of DDT is a success story. But a new threat has come to light.
The Chesapeake Bay has some of the finest fishing on the East Coast. The fishing season corresponds with the breeding season for osprey.
Ospreys are very tolerant of humans and will fish and nest close to populated communities. They often line their nests with a variety of natural and man-made materials. Some of the man-made materials ospreys pick up include paper, plastic rope and fishing line.
Osprey chicks have been found entangled in fishing line or impaled with fishing hooks. Adults have also been spotted entangled in line. Legs, wings and beaks can become so tangled that the birds are not able stand, fly or eat. Conservative estimates indicate that fishing line is present in 5-10 percent of all osprey nests on the Chesapeake Bay and surrounding rivers.
Anglers can reduce the injuries or deaths to osprey and other wildlife simply by discarding their fishing line and hooks. If possible, retrieve broken lines, lures and hooks. Always deposit them in trash containers or take them home. Help protect Chesapeake Bay wildlife.
The resurgence of ospreys after the DDT ban is a success story. This success can extend to the entire Bay and other wildlife as we continue to protect and restore habitats. Each of us can help by disposing fishing line, hooks and other potentially harmful objects into trash cans.
By doing things, we help to ensure that the osprey remains a familiar site on Chesapeake Bay.