Chesapeake Bay Ospreys Have Their Worst Breeding Season on Record

Ospreys nesting in the Chesapeake Bay had their least productive breeding season since monitoring began, with researchers pointing to food shortages as a major source of nest failures.

The Center for Conservation Biology at William & Mary reported that osprey productivity in 2026 fell to 0.25 fledged young per pair in Bay waters with salinity above 5 parts per thousand. In those saltier areas, 81% of monitored pairs failed to raise a chick to fledging. The center’s results drew on nest monitoring across 23 study areas throughout the Bay.

The breeding rate needed to maintain a stable osprey population is estimated at 0.8 to 1.3 young per pair each year. The 2026 figure in the saltier waters was well below that range. The center reported a decline from 0.51 young per pair in 2024 to 0.35 in 2025 and 0.25 this year.

Conditions differed across the watershed. Ospreys nesting in tidal freshwater areas produced an average of 1.04 young per pair, above the minimum maintenance threshold used by researchers. The contrast suggests the strain is especially severe in parts of the Bay where nesting birds depend heavily on marine fish.

Researchers identified food stress as the main driver of the widespread nest failures they observed. Osprey chicks were found underfed, and adult birds delivered fewer fish to some nests. Atlantic menhaden, a schooling fish rich in energy, are a key part of the ospreys’ diet. The center reported that menhaden deliveries to nests in some parts of the Bay have fallen by more than 80% since the 1980s, while the energy content of the birds’ diets has also declined.

The reasons for reduced menhaden availability remain uncertain. The Center for Conservation Biology said climate change, commercial fishing, shifts in fish distribution and later arrival in Bay waters may all play a role. The birds need abundant fish during the early nesting months, and a later influx may come too late to support young in the nest.

The center estimates that, if recent reproductive rates persist, the breeding population in the most affected areas could decline by about 14% a year. That projection is based on current demographic conditions and is not a certainty; the center also cautions that survival after chicks leave the nest is not fully captured by its monitoring.

The Chesapeake has long been one of the world’s most important breeding areas for ospreys. The new results indicate that the population’s health varies across the Bay, and that the low reproductive rates in saltier waters have become a serious concern for researchers tracking the species’ recovery and future.

Sources: Center for Conservation Biology at William & Mary; Center for Conservation Biology’s Atlantic Coast results; The Washington Post.