Baby ospreys are facing a greater threat of starvation because there are less menhaden in the Chesapeake Bay area, according to a new study from William & Mary Center for Conservation Biology.
In the report, researchers compiled breeding results in 511 osprey pairs in a dozen study areas, including in Hampton Roads. Breeding pairs were monitored throughout the nesting season, or from March to August, to measure success. To maintain population, ospreys need 1.15 chicks per pair of breeding ospreys. The collective reproductive rate for the population being monitored was 0.55 young chicks per pair.
Areas where ospreys relied on menhaden as a primary food source saw the biggest deficits in reproductive rates. Areas where catfish and gizzard shad were the main source of food had sustainable osprey populations.
“A large number of osprey pairs did not lay clutches during the 2024 nesting season,” reads a report from osprey researcher Bryan D. Watts. “These pairs arrived from wintering grounds in a timely manner (late February to early March). Most of these non-breeding pairs remained resident throughout the nesting season and defended territories but were never documented to lay eggs.
“This is the first time this behavior has been documented on a large scale within the Chesapeake.”
In Virginia Beach, breeding performance for ospreys had a “minor deficit,” or a reproductive rate between 0.8 to 0.9 young per breeding pair. Around the Elizabeth River in Norfolk and Portsmouth and on the Eastern Shore, the rate had a “moderate deficit,” or 0.6 to 0.8 young osprey per pair. Areas on the Peninsula and Northern Neck had a “major deficit.”
While nests can be threatened by several factors — such as weather and predators — Watts noted that observations, studies and pollution did not prove to have significant impact on the nests. Poor breeding performance throughout the main stem of the Chesapeake Bay in 2024, he wrote, was driven by the loss of young after hatching.
This can be seen in “asymmetrical broods,” or when one hatchling is able to grow larger than another hatchling born in the nest at the same time.
“Asymmetric broods were common and widespread throughout the main stem of the Bay,” Watts’ report continues. “On average, pairs in the main stem lost 1.1 young between hatching and fledging. Both the high failure rate of nests and the high frequency of one-young broods for successful nests were driven by brood reduction caused by food stress.”
Last month, the Atlantic States Marine Fisheries Commission voted to form a workgroup to consider additional restrictions on the industrial harvest of menhaden, and Virginia is currently the only state on the East Coast that allows for menhaden reduction fishing in state waters. Lawmakers this year did not pass a bill to fund a local study on menhaden populations.
Chris Moore, Virginia executive director for the Chesapeake Bay Foundation, said that menhaden industry management is “operating with a question mark” without the study. Existing data looks at menhaden populations across the East Coast, so not having Virginia-specific data makes it unclear how dire the situation could be.
“This year’s osprey data adds to the growing concerns about the number of menhaden in the bay and the importance of a robust menhaden population for species that depend on them for food and Virginia’s economy,” Moore said. “We must follow a precautionary, ecosystem-based approach to setting limits on the menhaden fishery.
“That approach must include the study of the industrial fishing impacts to the bay, as well as considering seasonal fishing closures from the Atlantic States Marine Fisheries Commission.”
Eliza Noe, eliza.noe@virginiamedia.com
