"The Gunnison sage-grouse is now in imminent danger of a series of local population collapses, which - when they occur - will result in extinction of the species," Fitzpatrick explained.
PHOTOS: Birds-of-Paradise Evolved in Lost Worlds
Efforts by public agencies and private landowners to help stabilize the bird's populations through private land easements, conservation plans and community education have not halted its decline, says Fitzpatrick.
Despite the bird's precarious status, getting a species endangered classification can be a long, laborious process.
For example the Dakota skipper butterfly, on the candidate's list since 1975, is now extinct in Indiana and Iowa. The Eastern Massasauga rattlesnake has been a candidate since 1982. And the Kittlitz's murrelet, a small bird, has been on the candidate's list for nearly 20 years.
"It is now urgent that the Gunnison sage-grouse be listed as an endangered species, and that a recovery team be assembled to fast-track recommended steps for halting the decline and imminent extinction of this remarkable bird," said Fitzpatrick.