To protect birds and motorists, engineers build a steel nest box on bridge
An osprey sits on its nest protected by a human-made basket.
CREDIT: New York State Bridge Authority.
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For the osprey that call New York’s Hudson Valley home, the bridges offer a tempting nesting ground. Positioned high above the fish-filled Hudson River, the large birds have a nest on top of the Bear Mountain Bridge, a 2,255-foot suspension bridge roughly 50 miles north of Manhattan. However, this is not the osprey’s first time on this scenic spot.
“We noticed that two years ago at the Bear Mountain Bridge, [that] they started building nests on top of the tower,” Craig Gardner, manager of maintenance for the New York State Bridge Authority tells Popular Science. “It’s not really an ideal spot for us, so we would go up and try to encourage them to go someplace else. But then last year, before we could get the nest, they laid eggs. So then we stayed away from the nest.”
An osprey sits in its nest atop New York’s Bear Mountain Bridge in May 2024. CREDIT: New York State Bridge Authority.
Ospreys are masters at swooping down into bodies of water to catch fish. Like other large birds of prey, they bring these fish back to their nests–whether they sit atop a tree or a large bridge. Osprey can be found in a variety of habitats, typically near any body of water with an adequate food supply. Thanks to ongoing conservation efforts in the Hudson River and its surrounding area, bald eagles, peregrine falcons, ospreys–and the fish that they need to survive–have seen a major recovery. The osprey are also the second most widely distributed raptor species, after the peregrine falcon, which can also nest on the bridges.
“The osprey actually build a nest. They will carry sticks up and create a nest,” says Gardner. “The peregrine falcons pretty much lay their eggs right on the stone. [For the peregrine falcons], we make a box and we fill it with stone so that they can lay their eggs in there. They’re opportunistic.”
In 2024, two chicks hatched in the Bear Mountain Bridge osprey nest. CREDIT: New York State Bridge Authority.
According to Gardner, last year’s osprey clutch successfully hatched and the chicks stayed up in the nest for most of the year. While the nesting birds are a good indicator that the ecological recovery of the Hudson, the nests can pose some risks to the approximately 20,000 vehicles per day who cross the Bear Mountain Bridge. The nest itself was about 250 feet above the roadway, so if a stick, branch, or even a fish falls out of it, cars and people below are at risk. The New York State Bridge Authority, which operates and maintains five bridges along the Mid-Hudson River Valley, typically tries to encourage birds to nest on the lower spans, closer to the river and away from cars. But in true New Yorker fashion, these birds appear to be seeking out the penthouse with spectacular views.
The solution: some human-built steel nesting boxes made especially for the ospreys. Instead of dismantling the nests, workers installed modular steel boxes so that the birds have a safer place to nest that contains any potential debris that might fall out.
Five crewmembers installed the steel nesting boxes in March. CREDIT:New York State Bridge Authority.
“We designed it so it would all be modular, so that we could take it up there,” says Gardner. “We actually have a motorized platform that one guy stands on, and it winches himself up to the top of the tower. It’s pretty similar to the basket on your desk. The birds use big sticks, so you could have the rod spaced fairly wide open, and then with the mesh inside.”
When all weighed together, the engineers took about 500 pounds of steel 350 feet in the air to install the nest boxes.
The osprey quickly returned and fixed up their nest after the crew finished installing the new baskets. CREDIT:New York State Bridge Authority.
“We took it up in components and assembled it on the top of the tower,” says Gardner. “They [the birds] were back there as soon as we left, rearranging the sticks and establishing their nest.”
There is no word yet on how many eggs–if any–are currently up in the nest. The Bridge Authority said that it will continue to share updates.
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