PREVIEW

For the first time since the 1980s, six sihek (Guam kingfishers) have been successfully reintroduced to the wild in Palmyra Atoll's tropical forests, as part of a global conservation effort aimed at restoring the species.

The milestone is the result of extensive collaboration by the Sihek Recovery Program, a group of conservationists from around the world - including the ZSL - committed to re-establishing the sihek in the wild with the ultimate goal of their return to Guam.

Nine young birds, four females and five males, were hand-reared over the last few months at the Sedgwick County Zoo, with support from zookeepers at ZSL’s Whipsnade and London Zoos, to prepare them for this historic rewilding.

Professor John Ewen of ZSL’s Institute of Zoology and Chair of the Sihek Recovery Program Team, said: “This is a momentous day that has been decades in the making. Wildlife globally is under threat, 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.”

On August 28, 2024, the sihek were transported from Wichita, Kansas, to temporary aviaries at The Nature Conservancy’s Cooper Island preserve and research station. Specialists have been closely caring for the birds, ensuring they safely acclimatised and received daily feedings before their release.

Each bird underwent a health examination before being fitted with a radio tracker, allowing the project team to monitor their movements and study how they adapt to their new environment. Since sihek are territorial, the team expects them to establish home ranges quickly, providing insights into their habitat use, foraging, and breeding behaviours. Supplemental food will also be provided to aid their transition.

The sihek was first listed under the Guam Endangered Species Act in 1982 and added to the U.S. Endangered Species List in 1984. Endemic to Guam's forests and culturally significant to the CHamoru people, the sihek went extinct in the wild in 1988 due to predation by the invasive brown tree snake. In response, the Guam DOAG and AZA rescued 29 sihek and launched an ex-situ care program, which now includes 127 sihek across 25 institutions nationwide.

Several AZA partners, including Brookfield Zoo, Cincinnati Zoo & Botanical Garden, Disney’s Animal Kingdom, and others, contributed to this effort by providing eggs or young chicks. The Smithsonian’s National Zoo and Conservation Biology Institute (NZCBI) played a key role in egg selection and transfer, while ZSL staff managed the care of the birds.

The Sihek Recovery Program partners include the U.S. Fish & Wildlife Service (USFWS), Guam DOAG, ZSL, The Nature Conservancy, Sedgwick County Zoo, AZA, and the International Union for the Conservation of Nature (IUCN).

Scott Newland, President & CEO of Sedgwick County Zoo, commented: “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. 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.”

Palmyra Atoll was chosen as the release site because it is free of invasive predators and fully protected. The atoll provides a safe environment for the sihek to establish a breeding population, with the long-term goal of reintroducing the species to Guam once the threat from snakes is mitigated.

Six of the nine sihek were deemed ready for release, with the remaining three to be released as they reach necessary milestones for survival. This flexible approach ensures that each bird is properly prepared for life in the wild. The partners plan to continue releasing sihek annually to establish at least ten breeding pairs.

This rewilding effort will allow the Sihek Recovery Program to monitor the birds' progress and refine future releases, bringing them one step closer to returning the species to its native home in Guam.