NARRAGANSETT — An osprey nest is wonderfully untidy. The one on a utility pole next to the channel at Jerusalem is 5 or 6 feet across and 2 feet high. Besides a tangled mess of sticks and other natural rubbish, it contains at least two pieces of derelict rope, some shredded plastic and what looks like a lobster pot buoy.

One afternoon last week, the tide was flooding up the channel into Point Judith Pond, tipping one of the channel buoys to the north. The osprey on the nest, however, was checking out a stranger.

With her single fledgling occasionally popping its head above the nest rim, the osprey — probably the female of the pair — wasn’t upset at the familiar state boatyard staff walking close by. But a stranger 50 feet away quickly had her up in the air, circling and scolding.

After having been nearly done in by the insecticide DDT, ospreys have made a dramatic recovery in Rhode Island, and along the rest of the Northeast seaboard.

DDT, widely used after World War II to kill mosquitoes, moved along up the food chain, becoming concentrated in predators such as the osprey, thinning their eggshells to the point of collapse

The population crashed. Between New York and Boston, “they went down from 1,000 pairs to 107 pairs,” said Richard O. Bierregaard, an ornithologist at the University of North Carolina.

The federal government banned DDT in 1972. There were still only 13 osprey nests in Rhode Island in 1978, and only 7 of those produced young ospreys.

By last year there were 108 active nests, which produced 151 young. “They’re clearly out of the woods,” said Lori Gibson, a state Department of Environmental Management biologist. She helps the ospreys make their comeback and has eased their sometimes-bumpy relationship with people. There are enough nests that Gibson has enlisted volunteers — she’s looking for more — to help find new nests and count their occupants.

OSPREYS USE Southern New England as a breeding ground, and you can watch for them from April through August. Migrants continue to pass through the area into the fall.

Gibson and her volunteers have spotted nests in practically every shoreline community, with many more inland around lakes and swamps. South Kingstown has about two dozen nests, and Narragansett more than a dozen.

Various authorities recommend the Great Swamp Management Area, in South Kingstown, and Napatree Point, in Westerly, for osprey watching. But Gibson’s list of nesting sites also includes several schools, the Port of Providence, wastewater-treatment plants in East Providence and Narragansett, and a long list of lakes, ponds and swamps.Even experts confuse ospreys with much-smaller seagulls at a distance. Closer up, ospreys look like other hawks. One the largest birds of prey in North America, their wingspan can exceed 5 feet. They have a white breast, belly, crown and forehead, a dark back and wings, and a black eye stripe.

Ospreys reveal themselves by the way they fly. With their diet almost exclusively fish caught alive, they circle high over the water, looking for lunch. They glide, then regain altitude by flapping vigorously.

They dive feet-first, sometimes disappearing under the water, and fight their way back into the air with the fish. Then they turn the fish around so that it’s traveling head first, to cut wind resistance.

Ospreys can be quirky. Gibson tells how a couple walking through the Great Swamp preserve stopped near an osprey nest. The bird circled, loudly letting them know they weren’t wanted. They didn’t get it.

“The osprey finally got fed up, picked up a snake, and dropped it on the couple,” Gibson said. The Web site of the Conanicut Island Raptor Project carries a photo of an osprey standing on a perch — with another osprey standing on its back. Osprey cheerleading? Nope, said project director Chris Powell. “That’s mating behavior.”

RIGHT NOW, the fledglings are getting ready to fly.

They are headed into great danger, their first migration, usually to Cuba and Hispaniola and then on to Central and South America. They stay south for two winters, and then return, often to where they came from. Experts estimate that most — perhaps as many as 80 percent — don’t make it back from that first migration.

Bierregaard, who uses satellites to track their migrations, thinks one two-year-old Rhode Island osprey named Conanicus, who would have ordinarily returned this year, met his end this spring in Cuba, where his signal stopped, probably shot by an angry fish farmer.

Shooting (or otherwise interfering with) ospreys and other migratory birds is a federal offense here, carrying up to a $15,000 fine and six months in jail.

A bigger problem is nesting sites.

“You’ll find very few natural nests anymore,” Powell said. “People just don’t leave dead trees around.”

“They want to nest above everything, looking down,” Gibson said, so they stake out perches like cell-phone and high-voltage towers.

That makes for trouble. She recalls a call at 10 one night after an osprey nest shorted out the electricity at Quonset Point. “Half the base had lost its power,” she said.

Pointing at the osprey nest at the DEM boat yard in Jerusalem, Don DeBerardino, the agency’s maintenance supervisor, said three transformers used to hang on that utility pole.

“Every time they’d build a nest, they’d short out the wires and blow out the lights for all three buildings,” he said. The transformers now hang on a different pole, much farther from the water. The ospreys kept the water view.

Gibson has a picture of an osprey nest the birds managed to build on the aft mast of a sailboat that was apparently not sailed often enough. She once got a call from a construction company whose crew went back to work on Monday to find an osprey nest under construction on top of their crane’s boom.

Ospreys have to compete with other ospreys and other birds for nesting sites, so they don’t give up a good location easily. If you just remove a nest, Gibson said, “they’ll just come back and re-nest.” Osprey-proof one utility tower, and they’ll move to the next one.

Because of that sort of difficulty, osprey lovers have built many man-made roosts, often a wooden utility pole with a platform on top. They have been erected with cranes, front loaders and backhoes, by hand and even sharpened to a point and dropped from helicopters like big darts, Powell said.

He said he’d help osprey fans arrange for a roost, if they’re willing to pay for the materials and make a contribution to osprey research.

The Conanicut Island Raptor Project, at / www.conanicutraptors.com/default.htm, has a variety of osprey information, plus a Web cam at an osprey nest with two fledglings in it on Jamestown.

The state Department of Environmental Management’s Osprey newsletter, and information about volunteering, is at www.dem.ri.gov/programs/bnatres/fishwild/pdf/ospr0407.pdf

blandis@projo.com