The sihek (also called Guam kingfisher or Micronesian kingfisher) has been extinct in the wild since 1988. (Michael Fitzsimmons / iStock)

As he starts his workday at Brookfield Zoo, Cody Hickman, associate director of avian care and conservation, is often greeted by a chorus of trills and squawks from the zoo’s population of Guam kingfishers.

“They call at dawn, at dusk. They’re saying, ‘This is my range,’” Hickman said. “It’s amazing to hear all these Guams call.”

This thrilling sound and sight of the birds, with their distinctive cinnamon-colored and bright blue plumage, is something Hickman never takes for granted. Brookfield’s 21 Guams (known as siheks by the indigenous CHamoru people of Guam) — all held off exhibit — are among the 127 that exist in captivity, and nowhere else.

Endemic to Guam, the sihek (pronounced see-heck) was last seen in the wild in 1988. It was all but wiped out, along with most of Guam’s other birds, by the invasive brown tree snake, which arrived on the island after World War II, having stowed away in a cargo ship.

“It always hits me ... not a lot of people have seen this bird,” Hickman said. “We hear the call (at Brookfield), but the people of Guam have not heard it. Chicago has more Guams than Guam.”

That could change.

At the end of August, participants in the Sihek Recovery Program, of which Brookfield Zoo is a member, took the first small step toward one day bringing birds and birdsong back to Guam.

At the end of August, nine captive-bred siheks arrived at Palmyra Atoll in the Pacific Ocean, where they will be released into the wild. (Thomas Mangloña / KUAM)

Nine siheks, including one that originated at Brookfield, were flown to Palmyra Atoll National Wildlife Refuge, a grouping of islets located in the Pacific Ocean roughly 1,000 miles south of Hawaii and some 3,700 miles east of Guam.

The birds will spend several weeks in aviaries while they acclimatize. Monitors from the Nature Conservancy and the U.S. Fish and Wildlife Service will be watching for signs that the birds are able to hunt for food on their own before fully releasing them into the forest.

What happens next is anyone’s guess.

Only two other bird species have gone from “extinct in the wild” to “critically endangered” after reintroductions. Those would be the California condor — one of the conservation movement’s great success stories — and the Guam rail (known as as ko’ko’ to the CHamoru).

The latter, like the sihek, was decimated by the brown tree snake. In the late 1980s, some 20 to 30 birds of each species — sihek and ko’ko’ — were salvaged from the wild in an emergency rescue operation and dispersed to various zoos in North America where they’ve been held and bred ever since.

There is now a small but self-sustaining population of ko’ko’ on a pair of snake-free islands near Guam. The goal for the sihek is to continue with annual releases at Palmyra until there are 10 established sihek breeding pairs and, fingers crossed, the first wild-born sihek since the 1980s.

“It’s pretty great to see this program reach this point,” said Hickman. “I many never go to Guam, but I know Brookfield Zoo has a role in this.”

Siheks are transported to a temporary aviary where they will acclimatize before their release. (Thomas Mangloña / KUAM)

Siheks first arrived at Brookfield in 1989, and the zoo has continually expanded its commitment to saving the birds.

In addition to managing anywhere from three to five breeding pairs annually — with 80 chicks having hatched at the zoo over the decades — Brookfield currently has the largest population of siheks in captivity, largely because the zoo has agreed to take in surplus males.

Siheks can live as long as 15 years, but males cease breeding after nine years. Because the birds also require a lot of space — “They don’t play well with other birds, so you can’t house them with others,” Hickman said — caring for these non-breeding (surplus) males meant some institutions reached maximum capacity and had to stop breeding, the opposite of what’s needed to keep a species alive.

“You want a pyramid with lots of young on the bottom,” Hickman explained. “When you have too many old birds, then you’re just holding them.”

By keeping surplus males, Brookfield freed up its sister institutions to continue their sihek breeding programs. The nine sent to Palmyra Atoll came from Brookfield, Cincinnati Zoo, Sedgwick County Zoo in Kansas, Disney’s Animal Kingdom and the National Aviary in Pennsylvania.

The chicks set for release were raised in isolation to guard against any diseases or pests being transmitted to Palmyra. Brookfield sent its sihek egg to Sedgwick for quarantine, and staff from the zoo spent a month total in Kansas to assist with the rearing of the chicks. 

“It’s such a big project. Our role has been the human care, to provide the eggs, to hold birds so other zoos can breed,” Hickman said. “It’s why we do the job — to help.”

Indeed, one of the aims of the release at Palmyra, according to U.S. Fish and Wildlife, is to prompt more institutions like Brookfield to join the recovery program, which would create more captive capacity and further increase genetic diversity among the sihek population.

An aerial view of the remote Palmyra Atoll, located roughly 1,000 miles south of Hawai'i. (Thomas Mangloña / KUAM)

Siheks released on Palmyra are being outfitted with tiny tracking transmitters so that partners in the reintroduction project can keep tabs on the birds’ movements and learn about their behavior in the wild, something researchers didn’t have time to study back in the ‘80s, what with the rush just to save the few that were left.

Researchers will also assess how much human intervention might be needed to support a wild population and refine procedures for future releases.

“The program needs a basis of what to expect,” Hickman said. “There are so many layers, this is a chance to see the whole picture, to get an idea of what are they going to do if they’re released on Guam.”

That’s a big “if.” Whether that day ever comes is perhaps the biggest question mark surrounding the entire program.

For the people of Guam, the sihek is something of a national symbol. “To them, it’s like if something happened to the bald eagle,” Hickman said. “It’s an emotional thing.”

But the bird’s return is entirely predicated on getting the tree snake (Boiga irregularis) under control.

It’s difficult to describe how destructive the snake has been on Guam — including causing hundreds of power outages annually by snarling power lines and slithering into transformers and electrical boxes — and how pervasive it remains, despite a decades-long push to beat it back.

Among the failed methods of containment: 2013’s ill-fated “mice drop,” in which thousands of mice laced with acetaminophen (poisonous to snakes) were dropped from helicopters into the jungle as deadly bait.

And still the snakes persist. Today they are estimated to number 10 to 20 per acre, and while that’s down from 50 per acre, the snake is still unchecked by any natural predator.

In some ways, Guam has become a test case for what happens when a key component like birds is removed from an ecosystem. Research has shown the forests have suffered — there are no birds to disperse seeds — and insect populations have mushroomed in the absence of birds to eat them.

Then there’s the psychological toll of living on an island without birds (three lizard species have gone extinct, too).

“Here, we’re so used to seeing so many birds, even in winter, and there you don’t have any,” Hickman said. “It’s a hard thing to comprehend.”

A male sihek named Yayas (pronounced Za-zass like “sass”), who originated at Brookfield Zoo Chicago, is among the nine that will be released at Palmyra Atoll. (Thomas Mangloña / KUAM)

Contact Patty Wetli: @pattywetli | (773) 509-5623 |  [email protected]