Some birds laid no eggs. Others tried to raise chicks but gave up. Many fledglings starved to death in the nest long before their parents flew south.

For the first time in decades this year, researchers on the Severn River in Anne Arundel County systematically documented the reproduction of the Chesapeake Bay tributary’s osprey. Their findings were grim.

Across 63 nests tracked last spring by Annapolis-based Operation Osprey, just 15 chicks survived.

The fish hawk’s low reproduction on the Severn is part of a distressing trend that’s played out across the Chesapeake Bay in recent years: After a decades-long comeback, many of the region’s signature raptors seem to have stopped laying eggs, while many of the chicks that do hatch die of hunger.

Surveyors with The College of William & Mary’s Center for Conservation Biology found that nearly three-fourths of osprey pairs surveyed last year in brackish portions of the bay produced no young at all.

The findings are especially concerning because of the Chesapeake Bay’s outsized place in the world of the sea hawks: Sometimes called “the osprey garden” of the world, the bay hosts 30% of the global osprey population.

Ken Green, Operation Osprey‘s president and cofounder, spent much of 2025 steering a boat to Severn River roosts, observing osprey parents and peering into nests with mirrors mounted on poles to monitor the health of their young. Though his organization has studied Severn River ospreys since 2023, this is their first year tracking the birds according to the strict protocol of the William & Mary center, which included the group’s data in a widespread bay survey released in October.

The spring got off to a promising start, but by summer Green could see that something wasn’t right. Mother ospreys abandoned nests while many hatchlings didn’t make it. Just a third of the nests tracked by Operation Osprey last year produced surviving juveniles — well below the threshold that the Center for Conservation Biology says is needed for the birds to maintain a stable population.

While the William & Mary researchers have pointed to the struggles of Atlantic menhaden, a staple of the osprey diet, as a driver of the bird’s woes in saltier reaches of the bay, Green said there seem to be plenty of fish in the Severn. Menhaden often swim “thick as thieves” there, he said.

Green speculates that the culprit of osprey struggles on the Severn may have its roots far from the watershed.

At the start of fall each year, ospreys depart from the Chesapeake Bay and migrate thousands of miles to South America. There, they settle in any of a dozen countries, winging across a region that spans from northern Colombia to the Brazilian Amazon to Argentinian mountains. They’ve been spotted at elevations as high as 12,000 feet — a far cry from their sea-level breeding grounds in the Chesapeake Bay’s marshes.

“They live a different life down there,” Green said.

Green wonders if something may happen in those months down south that impacts ospreys’ reproductivity. Once a wildlife biologist in Colombia through the Peace Corps, Green has a special interest in Latin America and has worked to establish connections between his organization and conservation groups there.

He hopes these partnerships will help scientists resolve what he calls “the mystery of the osprey.”

Others theorize that the problem lies closer to home.

Tom Guay, a longtime environmentalist on the Severn watershed, conducted his own tracking on the river this year, which he noted did not adhere to William & Mary’s strict protocols.

A resident of Winchester-On-the-Severn and former program manager with Operation Osprey, Guay and his group Eco-Ed Endeavors spent much of the spring and summer of 2025 counting osprey nests and hatchlings and leading educational trips for local students.

Of fifty nests with hatchlings that Guay identified on the Severn in early June, only eight had surviving fledglings by mid-August.

Guay shares concerns about the health of the osprey’s forage fish, but he hypothesizes that stormwater runoff has muddied the Severn waters, making it harder for birds to spot and capture their prey.

Bryan Watts, the longtime director of William & Mary’s Center for Conservation Biology, has studied osprey on the bay for over 30 years. Osprey populations crashed in the 1950s and ’60s as the proliferation of DDT insecticide poisoned birds and rendered others infertile, and, until recently, Watts had spent much of his career tracking the birds’ remarkable recovery.

The William & Mary scientist believes that osprey populations may be in decline across the bay. His survey this year found that in relatively fresh water tributaries of the Chesapeake, osprey reproduced enough to sustain populations, but in the more brackish areas that make up most of the bay, breeding has cratered.

The Severn’s waters are neither among the saltiest nor freshest of the bay, and Watts said its harder to predict osprey birth rates there compared to areas at the extremes of salinity.

Last year was the first in which researchers systemically surveyed the Severn since the mid-1990s, according to Watts. Though he doesn’t think there’s enough information yet to identify a trend on the Anne Arundel County river, he thinks Green and Guay are on their way to collecting meaningful data.

Recent osprey productivity alarms the longtime Virginia researcher, but he said panic about the birds themselves misses the bigger point: That these predators are an indicator for how other bay species are faring.

“I’m still not that concerned about osprey as a species,” Watts said. “I’m concerned about the bay ecosystem.”

Green sees it similarly.

While birth rates were low in the Severn watershed last year, the Annapolis researcher expects the ospreys will always be there. He awaits the moment each spring when he hears, in the early hours of a March morning, the call of an osprey, an announcement of the birds’ return after a long journey north.

“That means to me,” Green said, “that the universe is okay.”