The Guam Kingfisher Could Soon Return to the Wild After a 30-Year Absence

Once extinct in the wild, the California Condor now soars across the western United States thanks to successful breeding in captivity that allowed their later reintroduction to the wild. Now, a dedicated team is poised to do the same for the bright red and blue Guam Kingfisher. Endemic to Guam and extirpated on the island since 1988, these birds may soon fly free on a Pacific island—one more than 3,000 miles from their native home.

“It’s the first, long-overdue, much-needed step,” says Suzanne Medina, a wildlife biologist at the Guam Department of Agriculture Division of Aquatic and Wildlife Resources who helps lead the kingfisher’s recovery. “I am feeling very optimistic.”

As with most of the native bird species on Guam, by the 1980s the kingfisher was wiped out by invasive brown tree snakes, which were introduced to the U.S. territory shortly after World War II, creating a “silent forest” devoid of bird song. The Guam Kingfisher, known as Sihek in the indigenous Chamorro language, was spared from extinction when biologists brought the remaining 29 birds into captivity. Today, nearly 140 Sihek live in 25 facilities around the world, but their survival depends on a successful reintroduction to the wild.

“Getting them back into the wild, but also growing that captive population, are two things that need to happen to have the Guam Kingfisher persisting,” says John Ewen, a conservation biologist at the Zoological Society of London and member of the Sihek recovery team.

Experts say one of the main limitations to increasing captive Sihek numbers is space. Because of the species’ inherent aggression toward each other, the birds are kept in separate enclosures—sometimes even in different buildings—unless actively breeding. On top of that, Sihek suffer from inbreeding due to their depressed numbers. Because the population declined so precipitously, and only 16 of the rescued 29 birds raised young, the recovery team has to carefully plan breeding to maximize the species’ genetic diversity. Even with the strict management, inbreeding has caused a decline in Sihek lifespan and breeding success, increasing their risk of extinction. Expanding chick production—with a much-needed boost from wild birds after a successful introduction—is the species’ best shot at survival.

Ideally, biologists would reintroduce Sihek into their native Guam forests. But Guam still can’t sustain wild Sihek because of the brown tree snake’s unyielding presence, despite extensive eradication efforts—including dropping poison-laced mice from planes—that have helped dampen the snake’s population. “They are Guam’s bird, so it's very sad that we can’t actually put them back there,” Ewen says. Fortunately, the Endangered Species Act permits introducing listed species into new areas if their current habitat is too degraded to support them.

An official recovery team formed in 2020 to search for the Sihek’s potential new home. Cocos Island, a small island just one mile off the southern tip of Guam was the first candidate—the climate, habitat, and resources are essentially identical to the bird’s native home. However, the discovery of a flourishing population of brown tree snakes on Cocos squashed those hopes. Palmyra Atoll, a collection of 26 tiny islands more than 1,000 miles south of Hawaii in the Pacific Ocean, then rose to the top of the list.

After a successful rat-eradication effort in 2011, Palmyra is predator-free and the lush rainforest boasts a plethora of nesting materials and food for the endangered birds, including invertebrates and an endemic gecko species. Captive Sihek eat insects, anoles, and even live mice, but wild Sihek ate skinks and geckos on Guam. “It’s going to be really interesting to see what they will choose to eat once they are in the wild,” says Stefan Kropidlowski, the U.S. Fish and Wildlife (FWS) refuge manager of Palmyra Atoll National Wildlife Refuge.

In July, the recovery team visited Palmyra to finalize the introduction details. “Immediately you could see right away where the birds would fit on the atoll,” Medina says. “It’s definitely a place where the Sihek can thrive.” 

Thanks to a partnership between the Nature Conservancy and FWS, Palmyra also already hosts a small research station, increasing the project’s chances of success. “We're such a small, tiny little island that most people don't even know about—the fact that we can help another small, little, tiny Pacific island achieve their conservation goals is fantastic,” Kropidlowski says.

While the recovery team’s progress is promising, several regulatory hurdles remain before Sihek call Palmyra home. FWS is currently accepting public comments on the proposed introduction until September 30, 2022. And before the release, surveys will assess the possible impacts on native flora and fauna of introducing Sihek to Palmyra, which the team doesn’t expect to be an issue. Once finalized, Sihek can be released sometime in 2023.

Then, the hard work begins. “The remote location is ideal in some respects, and it can complicate things as well,” says Megan Laut, a FWS wildlife biologist on the Sihek recovery team. The only access to the island is by plane or boat, so the birds will experience little human disturbance. But that also means that supplies to build bird enclosures must be sent well ahead of the birds’ release. “If you don’t have the right piece of equipment, you can’t run out to the store and get it,” Laut says.

To minimize transporting foreign germs or bugs from birds traveling from multiple facilities to the atoll, 20 kingfisher eggs will travel to Honolulu, Hawaii where avian keepers will hand-rear chicks. Nine of those youngsters will eventually travel to Palmyra (the remaining chicks will fly to Guam for captive breeding) where they will live in small cages until they pass health checks. Finally, Sihek can once again fly free.

After release, biologists will monitor the kingfishers around the small island—another advantage of Palmyra—with tracking devices attached like tiny backpacks. “There’s a lot we can learn from keeping transmitters on the birds for a couple months,” says Erica Royer, the aviculturist who helped test the methods on captive individuals at the Smithsonian National Zoo and Conservation Biology Institute. “Are they finding food okay? And how far are they dispersing from the release site?”

Another unknown is when the wild birds might start breeding. In mainland facilities in the United States, they breed during the winter, but on Guam they can raise young year-round. Biologists are hopeful that these introduced birds—and a second group if the first release of Sihek goes well—will produce wild-born Sihek for the first time since the 1980s. Developing techniques and learning how the birds respond to being in the wild after such a long absence—from finding food to courtship—will help the recovery effort and pave the way for future introductions on Guam.

“Ultimately our objective is to reestablish birds on Guam,” Laut says. When will hinge on the success of the Palmyra release, and the snake eradication on Guam. But Medina is hopeful that a return to Guam could occur within five years of the proposed introduction. Sihek could be released on Guam where snake’s numbers have dipped, for example, or snake-proof fences might be used to protect any introduced birds. “There is still hope out there, and there are still actions that can be taken to help save our species,” Medina says. “This is just going to be the beginning.