2014-03-07 / Nature

Osprey Population Continues to Rebound

By Jack Kelly


Two juvenile Ospreys in the nest at Toppa Field last season, where one young bird is stretching its wings in preparation for its first flight. (Photo by Jack Kelly) Two juvenile Ospreys in the nest at Toppa Field last season, where one young bird is stretching its wings in preparation for its first flight. (Photo by Jack Kelly) In 1978, the Rhode Island Department of Environmental Management began an Osprey Monitoring Program to record the breeding success of the species and to evaluate its recovery from the devastating effects of the pesticide DDT.

The pesticide had seen worldwide use on crops to fight the ravages of insect infestation. However, there were some hazardous and deadly consequences for a number of wildlife species spanning the entire animal kingdom. There was also compelling evidence that long-term exposure could bring health risks to humans. DDT was banned by Congress in 1972.

Birds of prey, including the Osprey, Peregrine Falcon and the Bald Eagle, were brought to nearextinction by “eggshell thinning” in the early 1970s. These species are considered “apex predators”, at the top of their food chains. DDT had leached into the fields and contaminated surrounding waters and fish populations. Raptors who fed on the fish or waterfowl that ate the fish slowly built up deposits of the chemical in their reproductive organs. Their calcium metabolisms were mutated by the pesticide and the birds produced thin, weakshelled eggs that crushed under the parents’ bodies during incubation. Generations of young birds were lost.


Jack Kelly, a native Newporter, is a wildlife photographer and nature enthusiast who enjoys sharing his experiences with others. Jack Kelly, a native Newporter, is a wildlife photographer and nature enthusiast who enjoys sharing his experiences with others. Ospreys are the only birds of prey that eat fish exclusively. The average adult is about two feet long and has a wingspan of approximately 5.5 feet to almost 6 feet. The female of the species is about onethird larger than the male and has a stronger, thicker neck than the male. Both sexes have dark brown plumage above and white below and the underwings are a mottled brown and white.

Adult birds have yellow eyes, a dark eye-stripe and a short crest on the head. Some adults display a “necklace” of brown feathers on their white breasts. A juvenile fledgling has red eyes and a checkerboard pattern of white and brown plumage on its wings.

Ospreys hunt by hovering over both freshwater and saltwater bodies, then plunging down to grasp fish with its open talons, which are lined with retractable barbs called “spicules.” Ospreys also possess a rear opposable toe that allows for grasping or perching. Once an Osprey has seized a fish, it turns the catch to a forward-facing position so that the bird is aerodynamically sound in flight.

The first year’s effort by RIDEM revealed that there were only 12 active Osprey nests in the state, with 13 fledglings. However, as the effects of the pesticide dissipated over time, populations began to grow with expanded nesting sites. RIDEM continued the monitoring program through 2009, when it was turned over to the Rhode Island Audubon Society.

In 2011, the society began a program that would precisely locate every Osprey nest in the state through the use of global positioning satellites (GPS). This remarkable effort was completed during the 2012 nesting season.

According to Eric Walsh, Audubon’s Osprey monitoring co-manager, “Last year’s program involved over 70 volunteers inspecting 209 known nest sites. Of these, 138 were active and 96 were successful in producing a total of 168 fledglings. The Rhode Island breeding population produced an average of 1.75 fledglings per successful nest and 1.22 fledglings per active nest. There were 50 inactive nests and 8 “housekeeping” nests, meaning a nest where Ospreys are present but with no incubation. Often these nests are built by sub-adult Ospreys not quite ready to mate.”

Walsh is optimistic about the state’s Osprey population. “In our region, studies have shown that the breeding rate needed to balance adult mortality is 0.8-1.0 fledged young per active nest,” he said. “Rhode Island had a 1.22 fledged per active nest this past season, which indicates that population growth is likely to continue.”

Aquidneck Island hosted eight successful nests during the 2013 breeding season that produced 11 fledglings. One Newport nest, located in the cell tower at Toppa Field, is of particular significance to me. Since 2010, my friend Mark Andersen and I have been the volunteer monitors for this site. We have watched this nest since it was first established by a newly mated pair in 2006. The building of the nest is a part of the pair bonding and mating ritual of Ospreys. We have observed the intricate courtship rituals of these unique raptors, and witnessed their struggles as they fed, raised, and protected their young.

Over those eight seasons, the adults raised 19 fledglings. In 2008, we watched the two adult birds mourn the loss of one fledgling that was caught by a gust of wind and flung into a wall. The parents were inconsolable as they pushed and prodded the body of the dead young bird in attempts to animate it. It was a heart-rending sight.

The Audubon Society is seeking volunteer Osprey nest monitors for the 2014 season. Interested parties should contact John Scoones, volunteer coordinator, at jscoones@asri.org or at 401-949-5454 x3044.

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