A comeback story more than 20 years in the making is being celebrated as 'a tremendous success story' by the U.S. Fish and Wildlife Service (FWS).

The Fender's blue butterfly, previously listed as "endangered" under the 1973 Endangered Species Act, will be upgraded to "threatened" as of Feb. 13, the agency reported on Jan. 11. Native to the Willamette Valley of Oregon, Fender’s blue butterfly was thought to be extinct in 1937 but was rediscovered in 1989, the announcement reports.

“This is a tremendous success story – to go from nearly extinct to on the road to recovery,” Craig Rowland, acting state supervisor for the Service’s Oregon office, said in the release. 

Decades of development and fire suppression had altered and reduced habitat for the butterfly and other species, the agency reports. The Fender's blue butterfly was listed as "endangered" in January 2000, according to the report; in 2010, the final recovery plan for prairie species of western Oregon and southwestern Oregon, including the Fender's blue butterfly, was released. The recovery strategy included restoration and maintenance of several viable populations through protecting the remaining bits of prairie habitat and areas that could be restored to habitat, the plan states. 

 “These areas should be restored to functional prairie ecosystems with management that restores and maintains a diversity of native species typical of these prairie communities," the FWS reports in the plan.

Rowland said getting to the point of being able to downlist the Fender's blue butterfly was due to "successful partnerships with landowners, conservation agencies, businesses, other agencies and the work of our national wildlife refuges."

Several landowners are participating in agreements to assist the recovery of prairie species, including the Willamette Valley National Wildlife Refuges and the Partners for Fish and Wildlife Program, the agency reports, "to improve and maintain prairie habitat on their private lands. 

"This partnership brings collective resources to the table while providing landowners with management flexibility and regulatory certainty," the FWS states in the report. "The private lands conservation efforts combined with those on national wildlife refuges are essential for the butterfly’s recovery."

The number of sites where Fender's blue butterfly can be found has quadrupled since 2000; it now inhabits more than twice the acreage it did in 2000, when it was first listed as endangered. The butterfly can be found from mid-April through June in Benton, Lane, Linn, Polk, Washington, and Yamhill counties in Oregon, according to the report.

"This is yet another species that is making incredible strides in Oregon,” Rowland said.