FERN ACRES, Hawaii — Amy Durham wound the straps under the wing, over the wing, under the other wing, over the other wing, making sure the backpack-like device stays comfortably strapped to the Hawaiian hawk for many months.
These San Diego Zoo Wildlife Alliance researchers are trekking around the mountainous jungles of Hawaii’s Big Island not just to understand the ‘io, one of the state’s only birds of prey, which is considered at risk. It’s crucial, too, for restoring an even more endangered bird species — the ‘alalā, or Hawaiian crow.
Known for its problem-solving abilities, the Hawaiian crow is one of the most remarkable bird species in the world. The ‘alalā, whose name means to “yell” in the local language, is one of the only birds in the world known to naturally use — and even make — its own tools.
Yet this distinctive crow that many dub “very intelligent” has been extinct in the wild for two decades, with the only about 120 alive in human care today.
So far, plans to repopulate Hawaii’s forests with its native crows have been upended in part by the ‘io. The hawks are the crows’ natural predator, and have come after the corvids during prior reintroduction efforts.
By tracking the hawks, scientists with the San Diego Zoo Wildlife Alliance and Hawaii’s Department of Land and Natural Resources are trying to figure out where it is safest to reintroduce the crows so they can again thrive in the wild. At the heart of their research is a riddle: How do you protect two rare birds when one keeps attacking the other?
“They’ve coexisted for many, many, many years,” said Bryce Masuda, conservation program manager for the zoo. Now his team is trying to get these two bird species found nowhere else on Earth to coexist again.
Ever since people set foot in the Hawaiian archipelago, humans have been enthralled by the islands’ crows.
Its glossy black feathers adorned Native Hawaiian robes. Its imposing beak and piercing eyes led some families to regard the ‘alalā as a manifestation of an ‘aumakua, or “family god” that watches over them.
When Capt. James Cook arrived in Hawaii in 1778, many murders of crows stalked the islands’ volcanic hillsides.
Over the centuries, a variety of factors — disease, destruction of forests for farming and cattle ranching and predation by cats and other nonnative animals — conspired to drive the crow’s population down.
By 1992, there were only 13 ‘alalā in Hawaii’s forests. The last wild ones were spotted a decade later. The only ‘alalā known to exist today live in a pair of breeding centers run by the San Diego Zoo on the Big Island and Maui.
A picture of one of the survivors caught the attention of Christian Rutz, a behavioral ecologist at the University of St. Andrews in Scotland.
For more than a decade, he had studied a different corvid species called the New Caledonian crow. Without any training, chicks in New Caledonia, a French territory in the South Pacific, pick up sticks to collect grubs from crevices. At the time, no other crow was known to naturally use tools.
But Rutz suspected there were others. When he saw the Hawaiian crow’s straight beak and forward-facing eyes — features perfect for holding and manipulating twigs — he phoned the San Diego Zoo’s bird conservation center.
A manager told him the Hawaiian crows were always flying around with sticks in their bills. Rutz was stunned. “I booked myself pretty much onto the next flight to Hawaii,” he said.
In a paper published in the journal Nature in 2016 and subsequent research, Rutz, Masuda and others showed Hawaiian crows did more than pick up sticks to dig out morsels of food from logs.
The crows also manufactured their own tools — shortening sticks or stripping them of bark to make them fit better into tight, grub-filled crannies. “They will shape the right tool for the right job,” Durham said.
Living on isolated islands without much competition for insects, the two crow species likely evolved their dexterity with twigs independently of each other.
“They were just incredibly slick,” Rutz said.
At the zoo’s bird conservation center in Maui, a pair of ‘alalā awaiting reintroduction hopped from perch to perch on a recent day in their enclosures, landing with a thud. The birds flexed their tufts and ogled their human handlers with big, expressive eyes.
“There’s no other bird like it,” Masuda said.
Beginning in 2016, biologists tried to bring the ‘alalā back to the wild. Yet of the 30 released, 25 died or went missing. The other five were recaptured.
“There’s not one clear reason why the birds failed to thrive,” Masuda said. Some vanished without a trace while others succumbed to an untimely storm.
And then there was the hawk. Before releasing them, biologists trained the captive ‘alalā to avoid ‘io. In the wild, some of the released crows protected themselves by ganging up on aggressive ‘io. But other crows were predated by the hawks.
To tag the highly territorial hawks with GPS trackers in their renewed effort to reintroduce the crow, the San Diego Zoo team boomed the raptor’s namesake “eeeh-oh” screech from a portable loudspeaker.
Once a hawk was lured to a nearby perch, the team placed a ring-shaped wire cage with a mouse inside. Thinking it had a free meal, a hawk swooped in — and got its talons caught in plastic loops atop the trap.
“It’s actually an old falconry technique,” said Johnson, a biologist with the zoo who helped design the device.
After capturing the chocolate-colored male in December, Johnson held out each wing to measure the length, turned the bird over to look at its tail plumage and gently felt the muscle on the sternum.
“This is a very healthy bird,” he concluded.
On Johnson’s phone is a map lit up with blue, green and magenta dots — each the location of some of the 41 other previously tagged ‘io. Gaps show areas where they have yet to catch a hawk. Around the ankle of the most recently captured hawk the team placed a band bearing the number “42.”
The lightweight, solar-powered transmitters on each bird’s back ping nearby cell towers with latitude, longitude, altitude and other data multiple times a day. The contraption is secured with a single stitch so that it falls off harmlessly in about two years. At a cost of more than $1,000 a unit, someone will eventually have to fetch each transmitter.
“I can literally sit in the comfort of my air-conditioned office in San Diego and download the location data from each bird remotely,” said James Sheppard, an ecologist with the zoo. “It’s fair to say we’re in the golden age of wildlife tracking.”
Already the research has revealed some ‘io have much larger territories than others. One idea to reduce the chance of an ‘alalā encountering an ‘io in the wild is to place the crows near hawks with a lot of ground to cover.
But Masuda, the head of the conservation program, cautioned: “If we knew what they need to thrive, we would have released them a long time ago.”
With its backpack secure, the hawk got a middle-seat car ride to be released where it was first captured — and fill in another spot on the scientists’ map.
As Durham prepared to let it go, “42” looked at her with its saucer eyes. She raised her hand to move the bird’s attention toward a nearby stand of trees — and let go.
This article is part of Animalia, a column exploring the strange and fascinating world of animals and the ways in which we appreciate, imperil and depend on them.