The Center for Biological Diversity today filed a formal notice of intent to sue the U.S. Fish and Wildlife Service for failing to designate critical habitat and develop a recovery plan for the iiwi, a native forest bird in Hawaii.

The iiwi, also known as the scarlet honeycreeper, was listed by the USFWS a few years ago as a threatened species under the Endangered Species Act.

In 2017, the USFWS listed the iiwi, or Drepani coccinea, as threatened due to the extensive threats of mosquito-borne diseases, such as avian malaria and avian pox, as well as rapid ohia death and climate change.

But the act required the agency to designate critical habitat with its listing, and develop a recovery plan for the bird, the center said, and to date, USFWS has failed to do

“The Fish and Wildlife Service’s unacceptable delay deprives iiwi of badly needed protections,” said Maxx Phillips, the center’s Hawaii director, in a news release. “Without an actual recovery plan and protected habitat, these beautiful birds likely won’t survive.”

The national environmental nonprofit, which originally petitioned for the iiwi to be listed as threatened or endangered, addressed its 60-day notice of intent to Aurelia Skipwith, director of the USFWS in Washington, D.C.

The iiiwi, renowned for its bright, red feathers and long, curved bill, was once one of the most common forest birds in the Hawaiian Islands, but are now vanishing from nearly all of its former range.

Remaining populations of iiwi are mostly restricted to high elevation forests on Hawaii island, Maui and Kauai.

The birds are highly susceptible to avian malaria carried by invasive mosquitoes, the center said, with approximately 95% mortality when infected.

The iiwi have sought higher elevations to get away from mosquitoes, which usually cannot survive at cooler temperatures. Due to the impacts of climate change, however, temperatures at higher elevations of Hawaii are now increasing, meaning more mosquitoes are now invading mid- and high-elevation forests.

On Kauai, the center said warmer temperatures now allow mosquitoes to survive at all elevations, and the population of iiwi on that isle has decreased drastically since 2000, and is expected to go extinct by 2050.

Along with the devastating impacts of mosquitoes and climate change, rapid ohia death, a fungal disease that has decimated hundreds of thousands of native ohia lehua trees, further threatens the iiwi’s survival. Iiwi depend on ohia for nesting and foraging, and survive primarily on nectar from lehua blossoms.

Rapid ohia death, previously limited only to Hawaii island, continues to spread, and has now been detected on Kauai, Oahu and Maui.

Phillips said that species without designated critical habitat are half as likely to move toward recovery as species with critical habitat — and without protections for its critical habitat, the iiwi will continue to lose what little disease-free habitat remains.

Also, species with timely recovery plans for two or more years are far more likely to improve than those without.

The center last year also filed a lawsuit in federal district court in Hawaii, asking the USFWS to designate critical habitat for 14 imperiled Hawaii island species, including an anchialine pool shrimp, picture-wing fly and 12 plants.

“Time is running out for our iiwi,” Phillips said in a statement. “These incredible birds are facing populations declines of 70 to 90% over the next 80 years if action isn’t taken immediately to minimize the pressing threats of disease and habitat loss.