In late January, mating pairs of bald eagles are scoping for possible nesting sites, including on Martha’s Vineyard. Because it seems easier, they often make their home in a vacant osprey nest.
And, according to a local wildlife biologist, that is the reason why the Vineyard hasn’t hosted a baby bald eagle in local memory.
In 2020, the Vineyard’s first-ever bald eagle nest was spotted. Since then, four other pairs of the nation’s favorite bird have tried to hatch their eggs, without success.
Come early spring, representatives from over 100 pairs of ospreys return to the Vineyard from the Southern Hemisphere, set on reclaiming their homes. So far, in all five of the observed Vineyard bald eagle nests, ospreys have booted them out of their homes, destroying any eggs that were there.
Vineyard native Gus Ben David has worked with eagles all his life. He has rehabilitated them for the federal government, and is also a falconer.
Ben David recalls spotting immature bald eagles on-Island in the late 1960s, while he worked at Mass Audubon’s Felix Neck Wildlife Sanctuary in Edgartown. He would go on to direct that sanctuary for 36 years.
Ben David says that Massachusetts’ bald eagle population was low historically. And until 1995, the entire species was endangered.
“They weren’t even a factor in the early 80s and 90s,” he says.
Since then, Ben David highlights the positive impacts of conservation efforts, and legislation against hydrocarbon emissions as allowing the iconic bird to make a comeback. Bald eagles were removed from the less-severe threatened species list in 2007. In January 2023, the state Division of Fisheries and Wildlife reported that Massachusetts was home to more than 70 nesting pairs of bald eagles.
“This whole eagle thing has really been in the last 10 years — that we’ve really had eagles all over Massachusetts,” Ben David says.
According to Ben David, the Vineyard’s recent bald eagle attempts are largely due to a “hacking” project in the early 1980s at Quabbin Reservoir. Hacking involves raising and releasing young birds into the wild. The practice can restore an area’s population due to the “nest-site fidelity” of many bird species. Bald eagles can wander through multiple states for three or four years until sexually mature, but they tend to return to their birthplace to mate. The bald eagle pairs attempting to nest on-Island, Ben David says, may include the children of the Quabbin eagles.
While bald eagles have staked territory statewide, attempts on-Island thus far have been thwarted by an ubiquitous Vineyard raptor — ospreys. Ben David says that the Vineyard likely has New England’s second-largest osprey population.
And he would know. Starting in 1970, when the Vineyard had just two osprey pairs, Ben David started a program to install poles for osprey nests around the Island. “Anywhere you see an osprey nest on Martha’s Vineyard, it’s on one of my poles,” he says.
Any Vineyarder can tell that this project has succeeded. Ben David estimates that there are more than 150 poles now, and over 100 breeding osprey pairs as of last year.
Though ospreys are established on-Island, Ben David says that they are the main obstacle to any native bald eagles here.
“If you didn’t have an osprey population on Martha’s Vineyard, eagles would’ve been nesting here at least six or seven years ago, because that’s how long they’ve been trying,” he says.
The problem for bald eagles has been either that they choose an empty osprey nest for convenience, or start building in what ospreys consider their territory.
The male osprey usually returns around mid-March, ahead of its mate. He is not amenable to bald eagles in or near his nest. “When that male comes in, and he sees there is a pair of eagles on his nest, he absolutely is so territorial and so aerially adroit that he divebombs and drives and displaces those eagles from his nest,” Ben David says. This leads to what is called a “nest failure” for the eagles.
Ben David witnessed a struggle two years ago in Edgartown in the third week of March, after receiving a report that two ospreys were attacking a nesting female eagle. “[The property] had this big, huge field, with a big, huge oak tree in the middle with an osprey nest on it. That female [eagle] was actually incubating eggs…and I got a call from a lady…She says ‘Gus, I just drove in, and the osprey is out there.’
“It was spectacular…It would be like an F-16 and a 747. [Ospreys] are so adroit in the air. They’re like a fighter plane. And they were dive bombing that eagle. She was on the nest trying to sit down on the eggs, and that male [osprey] would come in and just rake right over her head,” Ben David said. “The eagle would jump up, which they do, and then put her talons up to try to grab the [osprey], and down they’d come. Of course, they’d smash the eggs. And then the eagle, psychologically…they’re almost destroyed. They leave.”
In addition to the nest failures at Edgartown and Squibnocket, Ben David says that ospreys have destroyed three nests along North Road.
Although bald eagles are outnumbered and outmatched, whether they reproduce on-Island is a matter of time and chance.
“Until a pair of eagles, young eagles, find a neutral territory and are able to successfully breed — once they do that, then the territorial imperative switches to them. Once they’ve raised their young, then when they come back, in other words, they have their nest,” says Ben David. “A pair of ospreys are not going to come in and displace them, because they don’t have a territorial imperative to do that.”
And if one osprey from a pair dies while off-Island, that can leave a space open for bald eagles. Ben David recommends against displacing ospreys to make life easier for eagles. “[There is] nothing you can do…It’s all natural. It will all take its course in time,” he says.
He adds that the range of territory an osprey defends varies per individual.
The Vineyard eagles that have experienced nest failure will also likely try again. Ben David thinks that at least two pairs of bald eagles will try this year, if not three or four. “I just hope that they can get going so we can have a population of bald eagles, more or less,” he says.
It is possible that you will spot bald eagles nesting on your property in the coming months. The Vineyard’s first nest was found at Squibnocket, after an eagle was seen bringing sticks to an osprey pole. Ben David says that the eagles also prefer big trees like white pines or pitch pines. If eagles choose to nest near you, Ben David says to leave them alone and admire from afar. “They could be building a nest and all of a sudden somebody walks in too close, and they’ll desert and stop that effort dead in its tracks.”
Ben David is often one of the first to know when a bald eagle nests on-Island, and when he knows exactly where one is, he keeps it to himself. “People call me because they trust me with wildlife. And if somebody, say, has got a bald eagle on their property no one knows about, we don’t tell anybody about it…Everyone wants to photograph them. So we keep a low profile and we keep people away from them…They’re going to find out sooner or later. You know — Vineyarders.”
Ben David adds that bald eagles do not harm small pets, though there can be rare exceptions if the eagle is injured or otherwise desperate for food.
During an interview while he was looking out at the many ducks and geese on his property, Ben David was ready for any bald eagles this year.
“We’ll see what happens,” he says.