When the aviary door swung open, offering the five young birds their first taste of freedom, they took note but stayed put at first, watchful.
The glossy black birds are among only about 110 ʻalalā, or Hawaiian crows, left on the planet. Their species has been extinct in the wild for two decades, and previous efforts to reintroduce them have yielded only lessons. In November, a group of nonprofit, state and federal partners tried again, but with a twist: Instead of returning the crows to their native range, the forests of the Big Island, the team released them on Maui.
There, the thinking goes, they’ll be safe from hawks, which killed a number of crows during earlier reintroduction efforts on the Big Island. If the crows can thrive on Maui, scientists and wildlife officials say, it will be a major step toward one day restoring them to their home island.
“They are shouldering all of the hopes of their species,” said Alison Greggor, an ecologist who helped lead the reintroduction for the San Diego Zoo Wildlife Alliance. “They are the future.”
The failure of earlier releases wasn’t for lack of effort. In the late 2010s, trying to instill a fear of hawks in the captive-raised birds, keepers played hawk sounds and moved a taxidermied hawk over the aviary while playing crow alarm calls. They placed a live hawk outside the enclosure with a dead crow skin under its feet.
Of 30 ʻalalā released between 2016 and 2019, many survived for more than a year. But over time they dwindled, and in 2020 the last five survivors were brought back into human care. Hawks are believed to have killed about seven, so they weren’t the only danger. But they were a factor that could be controlled by shifting to Maui.
A federal assessment found the introduction would not have any significant environmental effects on Maui. Still, introducing species to new places has sometimes come with disastrous ecological consequences. Hawaii’s native birds, for instance, have been devastated not only by rats but also by mongooses that were introduced in the 1880s in a failed effort to control the rats. Introduced deer and sheep have degraded the state’s forests.
However, according to research cited in the environmental assessment, Hawaiian crows or a “very closely related species” once lived on Maui. That suggests that other plants and animals in the ecosystem could be somewhat adapted to the presence of the birds.
“There is always risk,” said Aníbal Pauchard, an ecology professor at the University of Concepción in Chile who helped lead an intergovernmental report on invasive species. But Dr. Pauchard, who was not involved with the ʻalalā effort, said the environmental assessment appeared thorough and noted that moving a species between two neighboring islands was far less dangerous than a relocation further afield.
“I think this is a desperate situation, and they are doing the right thing,” Dr. Pauchard said, emphasizing that careful monitoring would be critical.
As climate change upends ecosystems, the debate over such animal relocations is likely to increase.
Hawaiian crows are intelligent birds known to use sticks as tools to dig insects out of holes. They are of great cultural importance, and once helped maintain native forests by dispersing seeds. But throughout the 20th century, their numbers declined. Commercial logging, deforestation for pasture, introduced predators and disease devastated the species. A Hawaiian crow was last seen in the wild in 2002.
The November release, announced on Wednesday, was the first in five years. The birds will get supplemental feeding for at least the first several months. Given the absence of hawks on Maui, the birds weren’t exposed to that version of anti-predator training. But the team tried something similar with cats and barn owls.
“We did have a live cat on hand and tried to get it to stalk right next to the aviary,” Dr. Greggor said, but the crows were intimidating. “I think the cat was pretty scared.”
When it was time to move the birds to the release site, Hawaiian cultural practitioners offered a blessing. The crows spent six weeks acclimating in a new aviary. Each got a tracking device. Then, one morning in early November, researchers opened the door.
After a moment, a few of the birds approached tentatively. Then, one particularly gregarious female hopped out.
“She started perching on top of the aviary, the others were clinging to the wall, looking up at her like, ‘Hey, what are you doing out there?’ said Martin Frye, a research supervisor for the Maui Forest Bird Recovery Project. “It wasn’t long before they also figured out, ‘Oh, I can go out there, too.’”
Soon, the birds had flown high into surrounding trees.
The team watched as they started calling to one other and ripping up bark to get at the insects underneath.
“It was so cool to get to see them do those natural foraging behaviors right away, because these birds have been under human care their whole lives,” said Tess Hebebrand, an aviculture specialist with the project. “They’ve never been out in the forest.”
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