Citizen scientist Kate Webb uses her bird's eye view of the osprey nest outside her window to help identify trends in the raptor population that serve as indicators of the overall health of the state's shoreline and river valleys.

Webb, who lives in Deep River, is part of a project launched by the Connecticut Audubon Society to monitor the state's osprey population, which is on the rise again after being driven to the brink of extinction half a century ago by the pesticide DDT.

Kate Scimeca, a researcher with the state Audubon Society and author of this year's Osprey Nation report, said the population of the distinctive bird of prey is growing "very, very quickly."

Volunteer stewards — there were 342 of them this year — observe nests every week or so from March to October to record annual milestones in bird life ranging from mating to raising young to leaving the nest.

Webb said she moved with her husband to Connecticut from New York City last year during the height of the COVID pandemic. That's when they looked out to find three ospreys carrying on like they were the stars of an avian soap opera.

"We could not be torn away from our window," she said.

It wasn't until she signed on with Osprey Nation after a visit to a local bird store that she learned the backstory to the drama. It turns out a cocky male osprey had wasted no time moving in with the resident female when her partner was waylaid on his annual flight from South America to the Connecticut shoreline.

"That got me totally involved," Webb said of the love triangle. Spoiler alert: Order was restored when the interloper left the couple to undisturbed monogamy.

Connecticut Audubon Society communications director Tom Anderson said the Osprey Nation project began in 2014 as a collaboration with the state Department of Energy and Environmental Protection to track the location and productivity of osprey nests in the state. He said environmental protection officials knew the number of nests was growing "but nobody had any idea how big or where they were."

The osprey population in the state prior to a 1972 ban of DDT had dwindled to about a dozen. It grew slowly over time to numbers Anderson described as "established and healthy."

He said the adaptable birds have taken to building their nests on man-made structures, such as parking lot light poles and police station communication towers, instead of limiting themselves to natural sites like dead trees, snags and cliff faces.

Data from the 2021 annual report released on Tuesday shows the number of fledglings — that is, osprey young that leave the nest — was up from 356 in 2015 to 858 this year. While part of that is related to there being more volunteers to track the data, there is also evidence that there are more osprey being born year over year.

Scimeca said an increase in osprey fledglings can be seen by comparing 2019 data with this year's numbers. There were the same number of volunteers in both years, but the number of fledglings rose by 208.

Last year was an anomaly because the pandemic led to a decline in the number of volunteers.

A decline in the health of the osprey population could mean something is amiss in the ecosystem.

"If we notice the number of osprey is falling or the number of fledglings per nest is falling, that would be an indication that there's something wrong somewhere," Scimeca said, "and it would give conservationists and biologists an idea that it's time to start looking for what the problem is."

That's what happened more than 50 years ago, when DDT was sprayed in salt marshes and other places to kill mosquitos, according to the state Audubon organization. It ended up in water bodies and accumulated in the fat of the fish that comprise the totality of the osprey diet.

Anderson said the chemical prevented osprey from producing eggs with enough calcium. "So they'd sit on the eggs, and they'd break," he said.

Old Lyme's osprey haven

The greatest concentration of osprey nests in the state is at the mouth of the Connecticut River on Great Island in Old Lyme, Anderson said. Assessor's records show the island is divided into several parcels owned by the state or the nonprofit Nature Conservancy.

The 500-acre marsh is accessible by boat and can be enjoyed by birders with scopes from the state boat launch on Town Landing Road. An Osprey Nation interactive map shows about 30 osprey nests situated across the wetland.

Anderson credited the marsh's size and relative isolation with making it conducive for osprey. That, and its location in the Lower Connecticut River Valley that have been recognized in superlative terms by those concerned with environmental protection at the local, state, national and international level.

"That entire lower part of the Connecticut River is of an ecological quality that is of global importance," Anderson said. "It is vast and while not pristine, it's still in great shape. It's got good clean water, it's got good habitats along the sides of the river. It's the kind of place that not just osprey, but any wildlife would thrive in."

Amanda Baker of Old Lyme is one of the osprey stewards keeping an eye on Great Island. This is her third season following at least four nests.

She said the season starts around April when Connecticut's osprey fly in from the Caribbean and South America. Typically, it goes like this: The male arrives first, with the female reaching the nest shortly thereafter. "They reclaim their nest if they're a returning pair, which many are," she said.

Eggs typically hatch in late April or early May, according to the Audubon Society. The male hunts while the female remains at the nest to care for the young until they grow enough to maintain their own body heat.

Baker said she watches from the state boat launch with a pair of high-powered binoculars to find the pairs in each nest. She may not be able to see all the way in, but she has learned that a predominantly hunkered-down stance indicates the female is nesting. Once the female begins to move around and the father starts making more fish deliveries, that's her sign the eggs have hatched.

"Soon, little heads start poking up," she said.

On leaving the nest

The period between hatching and leaving the nest is a brief 60 days for the young osprey, the Audubon Society reports.

Baker's most exciting observations have been when the parents bring back a fish so their squawking, exuberant adolescents can tear into it.

"It's rewarding to see these pairs come back year after year and raise their young successfully, and it's nice to see the population coming back," she said.

Over in Deep River, Webb noted the parents head out for South America before their young. She described it as painful to watch the young try to figure out how to live on their own.

"Their parents just leave them behind," she said, before softening her tone in defense of the couple. "Well, they've fed them all this time, they've gotten them ready, and the chicks have to start to feed themselves."

She said she's seen the young stuck in trees making horrible noises and has wondered if they'll make it.

Webb credited her osprey family with helping to get her through the isolation of the pandemic that first year and described mixed feelings when the little ones took off in the late summer.

The young will spend their first two to three years overseas before returning north to Connecticut to breed, according to the Audubon Society.

On one hand, Webb said it's almost a relief when the young prove themselves competent enough to leave the nest for good.

"But, it's also sad. Like right now, it's just nothing," she said, the view out her window turning stark as the refuge made of sticks awaits the pair's return. "Nothing until next spring, and then the whole cycle starts again."

e.regan@theday.com