Science

Overcrowding Might be Driving Bald Eagles to Nest on Beaches

On the Virginia Barrier Islands, five ground nests have been found in the past six years—something never before seen on the East Coast.

This past December, Audubon’s Cape Charles Christmas Bird Count made a surprising discovery while conducting its annual survey on a local Virginia Barrier Island: a Bald Eagle nest built directly on the beach. The group, led by ornithologist Dan Cristol, found the stick-supported structure propped up on a piece of driftwood, complete with a soft, grassy bed and picked-clean fishbones. "It was sitting right in the middle of the beach," Cristol recalls of the "enormous" nest. No eagles were around at the time, so the crew snapped a few pictures and continued on to not disturb the homeowners.  

Then, in March, another Bald Eagle beach nest was discovered on a different island. The two new nests bring the total number of beach nests found on the Virginia Barrier Islands up to five since the first two were discovered in 2013 and another in 2018. “I was surprised to see these two nests pop up so quickly at those two sites,” says Alex Wilke, an ornithologist for The Nature Conservancy, which owns and manages the islands where the nests were found. “It happened so fast, and we didn't have any indication it was going to happen.”

Bryan Watts, co-founder and director for the Center of Conservation Biology in Virginia, co-authored a paper on the 2013 nests and is the resident expert on the beach-nesting eagles. “On the ground here on the coast, it’s just not something you would expect to see, ever," Watts says. Even more surprising is that, unlike the three previous nests, the two new nests weren’t tucked safely behind the dunes. Instead, they were on the open beach, making them susceptible to washouts from storm surges or strong high tides. “The birds were taking a risk to nest up there,” he says. 

Nesting directly on the ground is rare for Bald Eagles, but not unheard of. Researchers have reported a few ground nests in forested areas in Florida and Texas and on other islands, and ground-nesting is the norm in some treeless regions, such as the Aleutian Islands of Alaska. But the recent beach nesting on the East Coast is a new and noteworthy behavior, especially given the fact that the birds are beginning to nest on the other side of the dunes, where the risk is much higher. “Nesting out on the ground on the beach, that’s really to me an unusual thing,” says Kenn Kaufman, bird expert and Audubon magazine’s field editor.

Watts thinks that the increase in ground nests and possibly even the turn to riskier locations is a response to an increase in Bald Eagle population numbers on the Virginia Barrier Islands. In the Chesapeake Bay, the birds dipped to about 60 pairs in the 1970s, largely due to the use of DDT. Since the U.S. federal government banned the pesticide in 1972, the area’s eagle population has bounced back to over 2,000 pairs, though Watts places the number closer to 3,000. Nationally, the population has similarly boomed.

Bald Eagles prefer tall trees in heavily forested areas for their nests, but with prime nesting sites at a premium, eagles in the area have had to start nesting in subpar trees like red cedar, shrubs like wax myrtle, and on manmade structures like water towers. Some have even gone so far as to nest on the roofs of old shacks. Now, it appears, they’ve also turned to the beach.

Ground-nesting along the Atlantic Coast might be a new trend for Bald Eagles, but the behavior is more common among Ospreys, another species that also rebounded after the DDT ban. When a habitat lacks elevated nesting sites—particularly trees but also artificial platforms like utility poles—Ospreys can resort to nesting on the ground. The birds mostly choose islands for their ground nests, which can place their humble abodes in the same watery peril as those of the eagles on the Virginia islands. 

In all, beach nesting might not be such a bad strategy. The islands the eagles chose provide plenty of prey, including turtles, waterbirds, and pelican young. They are also often free of ground-dwelling predators. As long as the nests can survive storm surges, nesting on the beach can be viable. Two of the three original nests remain, and both hosted parents and an eaglet this year. “From what we've seen, they can be successful by nesting out on these habitats,” Wilke says.

But nesting beyond the dunes is a much bigger gamble. The nest found in March successfully fledged one eaglet, but the one found on the Christmas Bird Count didn't end up producing any eaglets for unknown reasons (Wilkes suspects raccoons but can't confirm). Both nests are still intact, though Wilke says the sand around one nest shows signs of light water disturbance. With hurricane season just beginning, “it’s very possible they both could be washed out come their next breeding cycle,” she says.

If the nests are washed away, Kaufman is curious whether those pairs will learn their lesson and move, or if they’ll build again on the open beach. “Birds don't always do what we think they should,” he says.

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