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Fragile existence: Will Guam kingfisher survive the Palmyra Atoll experiment?

Updated: Feb 17, 2023


Guam kingfisher. Photo courtesy of Joe Alderman /Smithsonian Institution

By Mar-Vic Cagurangan


The Guam kingfisher is more than just a bird. Under the watchful eyes of scientists since it became extinct on island for 30 years, the Guam kingfisher— locally known as “sihek” — is emerging as an icon of hope for conservation.


Today, 152 sihek live in 25 facilities around the world, thanks to intensive captive breeding and protection efforts. The Fish and Wildlife Service is scheduled to release a small number of sihek back into the wild this year. But not on Guam, where its predator continues to run riot beyond control.


As long as the brown tree snakes’ unyielding presence on Guam remains uncontrolled, the sihek would never find its way back to its home island.


“We currently lack tools to eradicate brown tree snakes from Guam, and the continued presence of brown tree snakes throughout the landscape prevents the successful reestablishment of the sihek on Guam in the foreseeable future,” according to the Fish and Wildlife Service.


Hence the agency’s decision to designate Palmyra Atoll as a tentative location for the release of the bird's experimental population.


The sihek, Todiramphus cinnamominus, is a compact rusty-red bird with a long dark blue tail and short dark blue wings, a large charcoal grey bill and a black stripe through its eyes. In 1945, Guam abounded with its colorful presence but its population declined rapidly after the introduction of the brown tree and deforestation that resulted from World War II.


The last sihek was spotted in the wild in 1988, while biologists brought the surviving 29 birds into captivity.


“We plan to remove up to nine in the first year, and fewer than nine in subsequent years to ultimately achieve a target of 10 breeding pairs,” FWS said.


The bird’s release is long overdue, and keeping them in captivity for a longer period is not an option, according to biologists. Ethan Sapp and Cullen Wake projected that the number of Guam kingfishers will drop to 25 by 2040 if breeding is continued while the birds are in captivity. “A stochastic event, such as disease, could be lethal to the small-sized, captive population,” they wrote in a comment submitted to the FWS. They warned that continued captivity would lead to the loss of genetic diversity and encourage inbreeding.


“Not only will they lose genetic diversity, but it will also put them at risk for genetic adaptations that will occur while captive. This in turn will result in a loss of ability for the species to survive under wild conditions,” Sapp and Wake said.


But the Guam kingfisher’s survival depends on a successful reintroduction to the wild. While Guam has been ruled out, scientists weighed the suitability of Palmyra Atoll for the experimental sihek population. Located north of Kiribati, 5,800 km from its native home, Palmyra Atoll is currently owned and managed by the FWS, The Nature Conservancy and the Cooper family.


“We find that the continued presence of the brown tree snake on Guam means that the sihek's native habitat has been unsuitably and irreversibly altered or destroyed for the foreseeable future such that the proposed introduction of the sihek to Palmyra Atoll outside of its probable historical range is warranted and consistent with our regulations,” FWS said.


Sterling Brumbaugh and Jacob Owens of the Abraham Baldwin Agricultural College Wildlife Society advised FWS against the release of the Guam kingfisher as an experimental population “due to the likely death and lack of reproductive success of the released population.”


They noted that the proposed site for the reintroduction of the Guam kingfisher is not within the native range in which it naturally occurs.


Brumbaugh and Owens cited other ecological factors such as the presence of black drongos in Palmyra Atoll.


“Black drongos have been shown to show aggressive behavior toward other large-size carnivorous birds such as the Javan hawk-eagle, so it is plausible that the Guam kingfisher would receive the same kind of harassment,” they said.


Brumbaugh and Owens also cited the presence of pollutants in the atoll.


“An example of anthropogenic pollution is left over as a residual effect of rat eradication and the possible effects may lead to biological magnification within species on Palmyra Atoll,” they said, “With the effects of residual rat poison, Palmyra Atoll would not be an ideal choice to host an experimental population.”


Palmyra Atoll National Wildlife Refuge. Photo courtesy of FWS

FWS, however, said the introduction of the sihek to Palmyra Atoll is not intended to be a permanent introduction that would support a self-sustaining population.


“Depending on the circumstances, the service may either terminate the release program, or temporarily pause the release program to address identified issues before resuming,” the agency said, adding that its plan includes an exit strategy.


FWS said it would halt the bird’s release if “monitoring indicates the benefits from the Palmyra population no longer outweigh the risks to the species” and it “shows unacceptable impacts on the ecosystem that can be clearly causally linked to the introduction of sihek.”


So far, FWS said preliminary findings indicated that releasing sihek onto Palmyra Atoll “with the regulatory provisions” will “further the conservation of the species.”


“The potential loss of the experimental population would not appreciably reduce the likelihood of the survival of the species in the wild because there are currently no sihek remaining in the wild,” the agency said.


While hopeful about the outcome of the Palmyra Atoll experiment, conservationists are aware of some unknown variables.


“The sihek may not be fit to survive on their own in the wild due to adaptation to captivity, a lack of natural selection for multiple generations and problems associated with inbreeding,” Lane Harvey said.


Significant mortality can be expected in populations that are unfit to survive in the wild. Since no population has ever been released after the species was brought into captivity, there is a troubling lack of information on the release of the sihek and its current fitness levels,” he added.


Notwithstanding the dilemma, releasing the sihek is the only way to find out how and whether the endangered species will survive.


“Until the sihek can be observed in the wild once again, it will be unclear whether their captive breeding and rearing has affected them in this way, or to what extent they have been affected,” Lane said.


Unless there is an increase in the reproductive output of the species worldwide and more information is gathered, Lane warned, “the sihek will remain extinct in the wild, and may possibly go extinct completely.”




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