New London — Ospreys have nested atop a light tower in the parking lot of Ocean Beach Park for decades — some claim as far back as 1940 — returning each spring to breed, lay eggs and raise their young.

Something changed this year. The chicks are gone and the adults have abandoned the nest.

“A lot of people are concerned, myself included,” Nancy James said.

James is one of the more than 300 stewards volunteering for Connecticut Audubon’s Osprey Nation citizen science project, observing and documenting activity in more than 400 active osprey nests across the state.

The cause of the failure of the nest at Ocean Beach is something of a mystery but not all that unusual. Data collected from the Osprey Nation project, which started midway through the 2014 season, show failure rates for nests for 2015, 2016 and 2017 to be 20 percent, 8.5 percent and 12 percent, respectively.

The failure could be related to everything from newly installed bulbs in the light tower to a change in traffic flow in the parking lot to aggressive gulls.

James, a steward for the last four years, had observed the osprey mom on the nest, the father bringing in the fish and the telltale signs of chicks being cared for. That's why it was such a disappointment late last month to discover the chicks gone and the adults no longer nesting there. She said the adults do remain in the area, however.

The hope is the ospreys will return at some point or at the least make use of another nesting platform built by the nonprofit group Save Ocean Beach. James said the parents and the fledglings have used the wooden platform for drying out after rain storms, eating fish and just hanging out. To date, however, they have shown no desire to nest on that platform.

Ocean Beach manager Dave Sugrue said he’s disappointed but confident the ospreys would return and said he planned to work with James to investigate a cause for the empty nest.

“It’s always been there. At least as long as I’ve been here, and that’s 31 years,” Sugrue said of the nest. “I don’t think there’s much you can do. I think it’s just nature. We really enjoy seeing them come back every year. They’re not going to be gone for good. They’ll come back.”

Osprey, known as the “fish hawk” because they feed almost exclusively on fresh fish, can travel thousands of miles to overwinter as far south as northern South America. They return to Connecticut in March and osprey pairs typically will find each other and their old nest sites, laying their eggs in April.

Tom Anderson, spokesman for the Connecticut Audubon Society, said the reality with birds, as with all wildlife, is sometimes the young don’t survive. It could be for any number of reasons, from human disturbance to the presence of another predator.

The actual numbers of ospreys in Connecticut are the great success story, Anderson said, considering their population was devastated in the 1950s and 1960s due to the use of pesticides containing DDT. The pesticide, absorbed by the fish that ospreys ate, caused the birds' eggshells to weaken and crack prematurely, killing the chicks. A ban on the pesticide coupled with conservation efforts have led to a dramatic comeback and numbers that continue to rise.

“Every year we’re finding new nests,” Anderson said. “Osprey in general in this area are thriving. It’s mindboggling. We don’t know what the carrying capacity of the region is for ospreys. They’re big birds and require a lot of fish to eat.”

The increase in number of active nests — from 210 in 2014 to 424 in 2018 — is likely a combination of an actual increase in nests but also a boost in efforts by volunteers to find them.

James, who lives in Oakdale and works for the town of Waterford, said it was on a visit to Ocean Beach Park four years ago with a cousin that got her hooked. She had noticed the osprey nest in the light tower on the way out.

“Something sparked in me. I bought my first DSL camera to watch the nest and spent the next week watching their patterns and documenting,” she said.

She took a class on bird rescue and transport at A Place Called Hope, a rescue and rehabilitation center for birds of prey.

“I’m 57 years old now and never been as passionate about anything as much as osprey in my life,” she said.

g.smith@theday.com