Osprey numbers continue to decline

Photo by Bryan Watts.

By Linda Cicoira

A May 2025 survey conducted by the Center for Conservation Biology at William & Mary was disclosed this week, showing the osprey population along the seaside coast of the Eastern Shore of Virginia has nearly collapsed compared to historic accounts and benchmark surveys from the 1970s and 1980s.

The corridor is an “internationally important area for many migratory and resident bird species, including osprey,” said agency Director Bryan Watts. “The number of osprey pairs supported by this area during pristine times must have been tremendous.”

Harold Bailey reported “around 50” osprey nests on Hog Island alone and “several” within the middle section of Mockhorn Island during a visit in 1875, according to the report. By the height of the DDT era, the population had reduced dramatically.

Mitchell Byrd conducted an aerial survey of the seaside in 1975 as part of a broader survey of ospreys on the outer coast from New Jersey south through Virginia and recorded 68 pairs from Fisherman Island north to the Chincoteague Causeway. A resurvey of this area by Byrd in 1987 recorded 83 pairs, suggesting an ongoing recovery.

The recent survey shows pairs have declined nearly 90 percent over the last 38 years.

Beginning in the late 1990s, ongoing losses were recorded from sites used consistently for the previous 25 years. The number of vacant territories has grown over time, with many having been lost over the past decade.

“The underlying causes of this population decline are unclear,” Watts said. “Although there have been changes in nesting substrates, including duck blinds, dead trees, navigational aids, and nesting platforms over time, the availability of nesting substrate does not appear to be a primary factor.”

“Suitable structures remain widely available and many substrates that were used for extended periods are now vacant,” he continued. “It is possible that bald eagles may have impacted osprey along the seaside. The bald eagle population within the area has more than tripled since the 1980s. However, the density of eagles continues to be a small fraction of that found within the upper tributaries of the Chesapeake Bay, where ospreys continue to thrive,” Watts said.

“The most likely cause of the decline is prey availability,” he added. “However, no osprey diet studies have ever been conducted within this site, and we know very little about trends in fish availability.

During the 1970s and 1980s, the highest density of nesting pairs was skewed to the southern portion of the area around Fisherman and Mockhorn Islands. These birds could be observed flying out to the mouth of the Chesapeake to forage.