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Forest
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Guam
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John ewen holder image

Dr John G Ewen

Senior Research Fellow

Protecting the Guam kingfisher from invasive snakes

The sihek’s native island of Guam is only around the size of the Isle of Man but became overrun by 2 million invasive brown tree snakes. The first brown-tree snakes arrived in Guam in the 1940’s on shipping-containers. They were unlike any predator the native wildlife had seen before, and the impact on Guam was unprecedented. Most native bird, bat and lizard species were lost from the wild, knocking their ecosystem off balance. This has damaged all life on the island, even causing less trees to grow because there are so few birds left to disperse seeds. 

Sihek’s have been extinct in the wild for over thirty years, but through careful research we are working to restore their population. Progress has been made to create snake-free zones on the island to begin to revive Guam’s ecosystems - creating a healthier future for wildlife and people on the island.  

The Guam kingfisher

  • Snakes outnumber people 10 to 1 in Guam

  • These super predators have even been spotted twisting themselves into lassos to inch up to ‘snake-proof’ artificial bird boxes. 

  • Local people are disrupted by power outages caused by snakes climbing on powerlines, whilst chickens and even pets are killed by the snakes. 

Sihek chick in persons hands
© Colton Bolender National Aviary
Sihek chick sitting on a pink blanket
© Colton Bolender National Aviary
Sihek chicks

Sihek conservation  

The ZSL Institute of Zoology is working together to establish a healthy, wild population of these kingfishers. From our work with hihi in New Zealand to kestrels in Mauritius, we are experts in bird reintroduction projects. Now captive breeding populations are large enough, we are developing a conservation translocation plan for the species.  

Wildlife reintroductions are notoriously difficult, so our unique insight is crucial to planning everything from the method of release, to supporting the birds transition into the wild and predicting long term risks. The results of this project will provide more invaluable data which will be used to inform wildlife reintroduction projects globally. Helping advance the success of reintroductions for all wildlife, whether mountain chickens or greater one-horned Rhino.  

Sihek kingfisher in Guam
© M Kastner
Sihek (Guam kingfisher) sitting on branch
© Shutterstock

Genetic threats to the sihek 

The last few remaining siheks were saved from wild in the 1980’s, and without zoo conservation the species would have been lost forever. However, the small population has caused inbreeding to negatively affect the success of breeding. 29 wild sihek were captured and translocated to zoos in the US mainland before their extinction in the wild to start a captive breeding program, and today there are 135 siheks. 

Due to the small numbers of individuals that were captured from the wild and which successfully bred to establish the captive population, some inbreeding is inevitable in the sihek population. Inbreeding can reduce individual’s reproductive success and survival (this is called ‘inbreeding depression’), and therefore impact a population’s viability and extinction risk.

We found that inbreeding was having a substantial impact on adult male and female lifespan as well as reproductive success, so that more inbred individuals had reduced lifespans and fewer offspring than more outbred individuals.

To determine if this put the sihek at risk of extinction, we created a model of the sihek population to simulate what might happen under different management scenarios, including taking individuals from the captive population for release to the wild.

Through this research we created a framework to continue to grow the population through increasing breeding. By determining the best route to protect the long-term health of the population, our research has ensured the population remains strong enough to support the planned reintroductions. 

Scientific paper on sihek genetics 

Cutting-edge bird conservation

  • Mauritius kestrel in tree
    One of the most successful bird recoveries in the world

    Mauritius kestrel conservation

    The Mauritius Kestrel once looked destined for extinction, with just 4 remaining individuals. But we are building an exciting route to recovery.

  • Olive white-eye bird
    Saving the rarest bird in Mauritius

    Olive white-eye conservation

    With less than 150 pairs now remaining, our work is saving a species on the brink of extinction.

  • Male hihi close-up black head with a white streak, and yellow streaks along body
    Bringing hihi back from the brink of extinction

    Hihi conservation

    How this tiny bird is helping reframe wildlife conservation translocation programmes globally.

  • Pink pigeon in Mauritius
    Cutting-edge conservation in action

    Pink pigeon recovery program 

    From just a dozen individuals to hundreds - their story proves that together anything is possible.

  • Bird conservation projects

Protecting siheks – the Guam kingfisher 

The sihek population re-establishment programme is supported by the Guam Department of Agriculture’s Division of Aquatic and Wildlife Resources (DAWR), the US Fish and Wildlife Service (USFWS) and the American Zoo and Aquarium Association’s Guam Kingfisher Species Survival Plan participating institutions. 

Our impact 

  • The development of an effective conservation translocation strategy to re-establish a wild Sihek population, the only native Guam kingfisher species.  

  • Releases of sihek into the wild. 

  • A healthy wild population of sihek. 

  • A long-term species recovery programme, with continued monitoring of the established wild sihek population and the release-site ecosystem. 

Partners & Sponsors

Partners: Guam Department of Agriculture Division of Aquatic and Wildlife Resources (DAWR); US Fish and Wildlife Service (USFWS); American Zoo and Aquarium Association’s Guam Kingfisher Species Survival Plan participating institutions; Calgary Zoo; IUCN Conservation Translocation Specialist Group 

Sponsors: Guam Department of Agriculture Division of Aquatic and Wildlife Resources (DAWR); US Fish and Wildlife Service (USFWS) 

Fighting for wildlife

From leading field projects on tiny islands to influencing world leaders wildlife policies, we are there wherever nature needs us. Join us on our journey to restore the natural world.