The National Aquarium in Baltimore is seen at dusk. (Karl Merton Ferron / MCT)

The National Aquarium’s rainforest exhibit will be closed from March 2 through the fall as workers replace all of its 684 exterior glass window panes.

The expansive exhibit on the edge of Baltimore’s Inner Harbor is a re-creation of a South American rainforest, which guests can walk through to spot tropical birds, poison dart frogs and sloths. The glass surrounding the exhibit was original to the aquarium, which opened in 1981, said Jennifer Driban, the aquarium’s senior vice president and chief mission officer.

The new glass will come with a few upgrades. For one thing, it will be acid-etched, giving it a frosted appearance. That will diffuse the sunlight streaming into the exhibit. It also will make the glass panes more visible to wild birds, which sometimes would crash into the structure as they flew by.

The glass, which is double-paned, had become slightly cloudy over time due to sealing issues, Driban said. But aquarium staff found that the resulting reduction in direct sunlight actually helped some of the exhibit’s plants.

So, in a figurative sense, the aquarium is killing two birds with one stone. But really, fewer birds will perish.

“We’re able to help the species inside the aquarium,” Driban said, “but we’re also able to help the species that live outside the aquarium.”

It’s an effort supported by local group Lights Out Baltimore, which aims to reduce bird collisions in the city and records bird fatalities by surveying the city during migration season. The aquarium previously added a dotted film to some of its glass, including outside of its Australia exhibit.

After that, the number of bird collisions recorded outside the aquarium by Lights Out volunteers dropped off dramatically, said Lindsay Jacks, the group’s director. Of the buildings that the group monitored, the aquarium had been among the top five worst offenders. But during the 2021 migration season, they didn’t find a single dead bird outside the building, she said.

“The ‘Upland Tropical Rain Forest’ is not only a guest favorite, it literally defines Baltimore’s skyline,” National Aquarium CEO John Racanelli said in a statement. “These improvements will ensure the integrity of our building while accelerating our multi-year initiative to be Maryland’s most bird-friendly glass structure.”

The rainforest exhibit’s new glass also may make it easier to control its temperature, increasing the building’s energy efficiency. And the project will add LED lights along the border of the pyramid on top of the exhibit, which could shine purple or orange to show support for the Ravens or Orioles.

All the roughly 100 rainforest animals will berelocated to the back-of-house, in the aquarium’s Australia exhibit holding area and its Animal Care and Rescue Center on Fayette Street, Driban said.

Workers started relocating small birds and toads in the exhibit first. Starting in January, the animals were removed one by one as they were located, said Ken Howell, National Aquarium Curator of Australia and Rainforest, via email. Then came the sloths and more of the birds, he said.

“The scarlet ibis and the boat-billed heron were particularly tricky, as they spend most of their time high up in the trees. Our skilled staff was able to relocate them a couple of weeks ago,” Howell wrote.

The piranhas and other fish in the rainforest tank, along with the blue-headed parrot and sun conure are set to be moved Wednesday and Thursday. A few macaws, parrots and tortoises will stick around until the exhibit closes on March 2.

The flora inside the exhibit will remain, and it will be protected with a cloth barrier during the repairs, Driban said. Aquarium officials purposefully decided to conduct the repairs during warm-weather months, to minimize the impact on the rainforest plant life.

Crews will also replace 10 panes of glass at a time, to avoid leaving large sections of windows open to the elements, she said. The rest of the aquarium will remain open during the construction.

The aquarium received a $7 million grant from the state to fund the $8 million project, in addition to grants from the city, Baltimore County, the Abell Foundation and private donors.

“We wouldn’t be able to do this without their partnership,” Driban said.

The old glass will go to glass recycling company Strategic Materials, Driban said, and it will be used for fiberglass insulation and reflective glass beads for highway paint.

“It’s really incredible that we’ve found a partner, and we’re going to be able to recycle the glass that’s pulled out,” said Driban, adding that it meshes well with the aquarium’s conservation mission.