Global conservation partnership releases the first captive-bred population of Guam kingfishers into the wilds of Palmyra Atoll.

Conservation biologists are celebrating a momentous occasion: they just released a small group of Extinct-In-The-Wild Guam kingfishers into the tropical rainforests of Palmyra Atoll, where they are now flying free.

Long story short: Guam kingfishers are no longer extinct in the wild.

Thanks to the dedicated work of a global team of scientists to restore these birds to the wild, Guam kingfishers, or sihek, Todiramphus cinnamominus, are flying free for the first time since the late 1980s. Although sihek are now on Palmyra Atoll -- not on their native home of Guam -- this release is an important step closer to their eventual return home. (You can read more about that here and here).

"Today, the sihek were set free from their aviaries!" rejoiced Yolonda Topasna, Program Coordinator at the Department of Aquatics and Wildlife Resources with the Guam Department of Agriculture.

"Our Guam sihek, a symbol of our island's beauty, with their cerulean blue and cinnamon coloration mirroring our ocean blue water and red-orange sunsets, have been achieving the seemingly impossible."

"I'm sad to not be joining them at this milestone, however, I envision myself speaking CHamoru with them soon!" added Ms Topasna, who is a member of the indigenous CHamoru community (the first CHamoru Language Commission established "CHamoru" as the orthographically correct spelling in 1983).

"To our sihek: 'siempre un li'e' iyon-måmi tåno' yan tåsi. Nihi ta fan gumupu ya kumånta i CHamoru na kånta todu i lugåt' (you will certainly see our homeland, our sea, and together we will fly and sing CHamoru songs in all places)."

A total of nine chicks -- four female and five male sihek -- were hand-reared at the Sedgwick County Zoo during the last several months for this historic rewilding effort. Zookeepers from Whipsnade and London Zoos also helped raise the young birds.

Six of the nine sihek have already been released because it was determined that they were ready to deal with the challenges of wild life. The remaining three sihek will be released individually when they pass the essential milestones necessary to survive in the wild. This careful approach provides the fundamental flexibility to meet the individual needs of some of the birds who may require more time to prepare for their new life in the wild.

"This is a momentous day that has been decades in the making," said John Ewen, a professor at the ZSL's Institute of Zoology and the Sihek Recovery Program Team Leader. Professor Ewen's expertise focuses on recovering small populations of a wide variety of endangered species, often involving conservation translocation, and making the complicated decisions surrounding these efforts.

The birds' successful release is the culmination of decades of work by the Sihek Recovery Program, a global collaborative dedicated to reestablishing these birds in the wild in preparation for their eventual return to their native homeland in Guam. These collaborators are globally recognized leaders in animal care, conservation translocation, ecological restoration and wild population management and have used their expertise to recover several other extinct in-the-wild species, too.

"We are demonstrating that passion and partnership can make amazing things happen," noted Megan Laut, a recovery program manager with the U.S. Fish and Wildlife Service. "The diverse skill set and contributions of each partner have led us to this historic milestone and will inform our efforts to grow the global population of sihek and take meaningful advances to return sihek to Guam."

The sihek's dire situation was first officially noted in 1982, when they were listed under the Guam Endangered Species Act. But the birds' population crash continued, so sihek were then added to the U.S. Endangered Species List in 1984. Even that did not stop their decline: sihek have been extinct in the wild since 1988. Fortunately, the the Guam DOAG and AZA rescued the last 29 wild sihek, and these birds became the founders of an ex-situ population, which currently is numbers 127 adult sihek across 25 institutions.

"Wildlife globally is under threat," Professor Ewen elaborated, "and the success of seeing these birds fly in the wild once more highlights just how zoos, scientists and conservationists -- working with governments and decision-makers -- have the power to protect species and take huge steps in bringing them back from the very brink of extinction."

The sihek release process is quite involved. The young captive-bred birds were flown from Wichita, Kansas to Palmyra Atoll, then carried to temporary aviaries on The Nature Conservancy preserve and research station at Cooper Island on 28 August 2024. After the birds were released into temporary aviaries, specialists cared for them, ensuring that the captive-bred sihek safely acclimatized to their new home, and received daily feedings.

Prior to release from the temporary aviaries into the rainforests of Palmyra Atoll, each sihek was given a health exam. A tiny radio tracker was fitted to each bird so the project team can monitor their movements as they explore and settle in to the habitats across the atoll that are new to them. Additionally, supplemental food will also be provided to help the newly released birds transition to their new life.

"The National Aviary is one of only four institutions who participated in the important pilot study to help ready some of the sihek population for release into the wild," stated Kurt Hundgen, Senior Director of Animal Care and Conservation Programming at the National Aviary.

"The kingfishers in our Breeding Center trialed the same 'backpack' radio telemetry devices that they will use in the wild. These tiny trackers will help field researchers to monitor the birds' movements and survival after they are released," Mr Hundgen said. "We are so excited to see what insights the telemetry units will be able to provide to help guide conservation and land management practices in the future."

Sihek are a fiercely territorial species, so the team expects the birds will establish home ranges quickly, which will also help the team to locate and monitor the birds in the future. This intensive follow-up on the newly rewilded birds will provide insights on how they are adapting: their habitat use, foraging, and eventual breeding. Further, this rewilding effort on Palmyra Atoll will help refine and tailor future releases and monitoring techniques of sihek and other endangered wildlife.

"Palmyra provides a welcoming environment for the sihek and one that is conducive for monitoring their transition from human care to life in the wild," elaborated Stefan Kropidlowski, Pacific Remote Islands Marine National Monument Deputy Superintendent at USFWS.

"This is a historic milestone and a vital step for project managers as we learn from the sihek as they are actively adapting and exploring their new habitat," Mr Kropidlowski pointed out.

There are thousands of islands in the South Pacific Ocean: why was Palmyra Atoll specifically chosen as the sihek's first forever home?

"Palmyra Atoll is an ideal location for rewilding these magnificent birds on their journey back to Guam," replied Alex Wegmann, Lead Scientist for Island Resilience with The Nature Conservancy.

"It is one of the healthiest land and ocean ecosystems on the planet, is free of invasive predators like rats, is carefully studied and monitored, and is fully protected as a national wildlife refuge and TNC preserve," Dr Wegmann elaborated. "Extensive research shows Palmyra's forests are ideal for the sihek and that introducing it will have minimal effects on native wildlife there."

Sihek were almost eaten into extinction by invasive predators, particularly the brown tree snake, Boiga irregularis. This snake had been introduced to the island of Guam near the end of World War II. Since its appearance, the snake has since eaten all of Guam's native wildlife into extinction, including all of its bats and birds -- except, of course, for the few bird species that were belatedly rescued.

In contrast to Guam, Palmyra is a relatively pristine atoll that will provide sihek a safe home to thrive in and establish a breeding population, with the ultimate goal of one day returning the birds to Guam after the threat from snakes is addressed.

Palmyra Atoll is carefully monitored and maintained by a number of agencies. The Nature Conservancy manages a preserve and research station at Palmyra Atoll on Cooper Island. These facilities enable globally significant ocean, coral reef and island research and restoration, such as this important sihek project. Further, Palmyra Atoll is a U.S. Fish and Wildlife Service National Wildlife Refuge and is protected -- out to 50 nautical miles -- by the Pacific Remote Islands Marine National Monument, making it one of the largest areas of ocean and islands to be protected under a single jurisdiction in the world.

"AZA partners have proudly maintained the Sihek population in human care since 1988. Without the dedication of our aviculturists and the support of zoos, this release would not have been possible," pointed out Scott Newland, President & CEO of Sedgwick County Zoo, where the newly rewilded sihek were raised.

"Our work with this species has provided us with valuable knowledge, allowing us to tailor this release to give the birds the best chance for success. For AZA, this release represents the culmination of nearly 40 years of collaboration, research, and dedication aimed at seeing the Sihek flying back on Guam one day."

But the people who did the actual hands-on work of incubating the eggs and hand-feeding the chicks around the clock were a dedicated team of aviculturists and bird keepers.

"Having spent long days working around the clock to hand raise these precious birds, it's so incredible seeing them not only fully grown, but also now flying around Palmyra Atoll," declared Charlotte James, one of the London Zoo bird keepers who travelled to Sedgewick Zoo to help hand-rear the chicks. "Soon the whole flock will be out in their new forest home. It's such an honor to be part of this journey to not only return sihek to the wild, but also to one day return them to the island of Guam."

"It's significant to note that the last passenger pigeon died this month 110 years ago," recounted Aimee Owen, Senior Aviculturist at the Cincinnati Zoo. "Martha lived at the Cincinnati Zoo & Botanical Garden, which makes it even more exciting for us to be a part of this effort to bring an extinct-in-the-wild bird back to its native habitat. We hope that all nine birds stay healthy and raise chicks in their new home."

Already, the Sihek Recovery Program plans to supplement the new Palmyra Atoll population annually, with a goal of establishing ten breeding pairs of sihek.