Peregrine falcons have always been a somewhat rare sight in coastal Virginia.
They originally dwelled on the western side of the state, but were later introduced along the coast to help boost the population, which had been wiped out by pesticides.
The falcons are now facing their biggest threat in more than half a century: Bird flu.
“We’ve never seen anything like this,” said Bryan Watts, director of William & Mary’s Center for Conservation Biology.
At least a third of the state’s peregrines are typically on the Eastern Shore, and that population has dropped by 50% since 2022, he said.
Scientists have also seen a spike in younger birds breeding, suggesting that there are fewer adults around to fill in the gaps.
“There's less resilience in the population. The buffer is smaller,” Watts said. “Once we started to see the younger birds being recruited into the population, then we started to see more of a precipitous decline in breeding pairs.”
Peregrine falcons are famous for being the fastest animals on the planet, reaching a speed of more than 200 mph during hunting dives.
Historically, in Virginia, the falcons stayed around the Appalachian Mountains. They like to nest on open cliff faces and “high areas where they have a vista over the landscape,” including bridges, Watts said.
By the 1960s, peregrine falcons had disappeared from Virginia because of widespread use of the chemical DDT, which affected the birds’ ability to lay healthy eggs. The last known breeding at the time was in 1964.
But state officials, in partnership with conservation groups including Watts’ at William & Mary, began trying to re-establish the population in 1978.
Over the following 15 years, Virginia released 250 young captive-bred peregrine falcons, including along the coast. The first modern breeding happened at the Chincoteague National Wildlife Refuge in 1982.
About a decade ago, Virginia was supporting more than 30 breeding peregrine pairs, including some that attracted attention nesting on the Armada Hoffler Tower in Virginia Beach and in downtown Norfolk.
“There’s been a very slow recovery,” Watts said. “It’s still a tiny population here.”
Then came the latest strain of the bird flu, which has fueled the largest outbreak in wild birds ever recorded.
The strain originated in China in the 1990s among domestic waterfowl. In the 2000s, it started to break into Africa, the Middle East and Europe and arrived on America’s Pacific coast around 2014.
In 2021, the virus was detected in birds in the Atlantic Flyway, a major north-south “avian highway” for birds migrating along the Atlantic coast.
The following winter, “we picked up the first dead peregrine on the Eastern Shore that was killed by avian flu,” Watts said. “So the impact has been relatively recent, but it's been fairly dramatic.”
Peregrines are particularly susceptible to catching the bird flu because they eat almost entirely birds that carry the virus.
“It's a bit of a cruel twist,” he said. “The reason that the birds have done so well and recovered so well on the outer coast is because they're able to use the throngs of shorebirds that come through to raise their broods.”
But right now, many of those shorebirds are infected.
Peregrines further inland, in the mountains of Virginia, have fared better because they largely eat passerine birds, which have a lower infection rate, Watts said.
He said there’s not much to do except wait for this wave of the flu to blow over.
“Our hope is that our population can develop some immunity and that they can weather the storm,” he said.
“Most of the public, when they think about bird flu, they think about the price of eggs because of the impact on laying hens. But for those of us in the wildlife community, our concern is some of these threatened species and what impact avian flu may have on them.”
