Osprey Monitoring

Osprey in Flight

Every week, from April through August, volunteers in Rhode Island head forth to check on Osprey nests. The monitoring program, overseen by the Audubon Society of Rhode Island (ASRI), is a model for efforts in other states. The monitoring of Osprey (Pandion haliaetus) in RI began in 1977 by the RI Department of Environmental Management, and was taken over by ASRI in 2010. With one exception, data on Osprey nesting has been collected every year by citizen volunteers. Osprey numbers have increased annually, once the use of DDT was outlawed. The pesticide DDT accumulated in the food chain, causing major problems for birds like Osprey and Bald Eagles (among other species). DDT caused the shells of eggs to be thin, so thin that the weight of adult birds crushed them as the adults tried to incubate the eggs. Rachel Carson’s Silent Spring highlighted these impacts, as well as the harmful effects of other pesticides, helping to jump start the modern environmental movement. Once DDT was outlawed in the United States, Osprey, Bald Eagles, and other species began to return in numbers and to locations they had previously enjoyed. Monitoring and reintroduction programs began. I am responsible for monitoring four nests this year, three in Hopkinton, RI, and one in West Greenwich, RI. Three of the four are active, meaning they are occupied and the adult birds appear to be incubating eggs or attending to young. In all cases it is not possible to see into the nests, so I have to judge from the adults’ behavior.

Osprey have several popular names: fish hawk, fish eagle, river hawk, and even sea hawk. As these names suggest, they eat fish exclusively, but are neither eagles nor hawks. Rather, Osprey are the sole species in their biological family. They are a holarctic species, meaning they are found throughout the northern continents of the world. Osprey occur on every continent except Antarctica, although they do not breed in South America, heading south in winter months from their nesting territories in North America. Osprey always fly with their wings crooked in an “M” shape and have a dark patch on their “elbows”, actually the equivalent of their wrists. They have scales on their toes that help them grasp fish, which they capture by diving. Unlike eagles and hawks, Osprey can rotate one toe backwards, better enabling them to hold their prey with two toes forward, two backward.

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