Study says Chesapeake Bay Osprey reproduction falls to record low in 2026

Osprey reproduction in the Chesapeake Bay fell to the lowest level ever recorded during the 2026 breeding season, according to new monitoring results from the Center for Conservation Biology at William & Mary.

Researchers monitored 937 osprey pairs across 23 study areas stretching from tidal freshwater portions of the Chesapeake watershed to waters near the mouth of the Bay. The monitoring was conducted from March through August to measure nesting success and the number of young produced.

The results showed a sharp difference between osprey nesting in freshwater areas and those in saltier portions of the Bay.

Among 769 pairs nesting in waters with salinity above five parts per thousand, average productivity was just 0.25 young per pair. Researchers say osprey populations generally need to produce between 0.8 and 1.3 young per pair each year to remain stable.

By comparison, 168 nests monitored in tidal freshwater areas produced an average of 1.04 young per pair, exceeding the minimum level considered necessary for population maintenance.

The study found that 81 percent of osprey pairs in the saltier areas failed to produce any fledged young. Productivity in those portions of the Chesapeake has declined from 0.51 young per pair in 2024 to 0.35 in 2025 and 0.25 this year.

The Center for Conservation Biology says those numbers raise concerns about the long-term Chesapeake Bay osprey population, which has historically been one of the largest breeding populations in the world. Based on current reproductive rates, researchers estimate the breeding population could decline by an average of about 14 percent annually if conditions do not change, potentially resulting in a roughly 50 percent decline over the next decade. Researchers note, however, that the rate of decline would likely vary considerably across different portions of the Bay.

Researchers attribute much of the recent nesting failure to what they describe as food stress. Among the evidence cited are reduced food deliveries to nests, underweight chicks, smaller broods, abandoned nests and documented cases of chicks starving.

The Center says declining availability of Atlantic menhaden appears to be an important factor. Menhaden have historically been a major food source for Chesapeake Bay ospreys because of their abundance, schooling behavior and high energy content. In some areas, researchers report that delivery of menhaden to osprey nests has declined by more than 80 percent since the 1980s.

However, researchers say the underlying reason for the reduced availability of menhaden to ospreys remains uncertain.

The Center lists several possible contributing factors, including climate change, commercial fishing, changes in where menhaden are distributed and the possibility that large numbers of the fish are entering the Chesapeake later in the summer. The researchers did not identify any single one of those factors as the definitive cause.

Other factors can also contribute to osprey nest failures, including storms, predators, human disturbance and heat stress. The Center says the patterns observed during the 2026 season were most consistent with widespread food shortages rather than those other causes. Other studies have linked increasing eagle numbers with declines in ospreys, potentially through territorial aggression or predation. But this study said there was no evidence that competition with eagles for fish or nesting sites was responsible.

The monitoring included study areas throughout Virginia and Maryland, including the Bayside Eastern Shore, Mobjack Bay, the York, James, Rappahannock and Potomac rivers and other portions of the Chesapeake watershed.

The project included contributions from the Center for Conservation Biology, U.S. Geological Survey, Virginia Department of Wildlife Resources, Virginia Aquarium and Marine Science Center, Washington College and several other conservation organizations.

The findings continue a broader research effort examining whether declining reproductive success in saltier portions of the Chesapeake represents a long-term threat to the Bay-wide osprey population.