Sometimes it’s a cause for celebration when species get taken off the endangered list. Conservation efforts have brought giant pandas and snow leopards back from the brink of extinction in recent years, manatee and grey wolf populations are recovering, and tiny litigious snail-eating fish are no longer facing an untimely end.

But there’s another, far more grim reason that a species might stop being endangered: it doesn’t exist anymore. That’s what has officially happened to 22 animal and one plant species this week, which the U.S. Fish and Wildlife Service has declared should now be considered extinct.

“Each of these 23 species represents a permanent loss to our nation’s natural heritage and to global biodiversity,” Bridget Fahey, who oversees species classification for the Fish and Wildlife Service, told the New York Times. “And it’s a sobering reminder that extinction is a consequence of human-caused environmental change.”

Among the departed is the ivory-billed woodpecker, last officially seen in 1944 – although a handful of unconfirmed sightings in the years since then have kept birdwatchers returning to the swamps of the Gulf States in the hopes of spotting its majestic red crest. Also on the list is the poʻo-uli, or black-faced honeycreeper. This tiny bird, previously endemic to the island of Maui, was only discovered in 1973, but by the end of the 1990s there were just three left in the wild. After the only male died in 2004, the two females were never seen again.

The announcement this week marks the beginning of a 60-day comment period, during which scientists and members of the public can submit information to the Fish and Wildlife Service that they think is pertinent to the decision. After this time, the changes will be made final – but many researchers warn against calling time on the species too early.

“Little is gained and much is lost,” when a species is declared extinct, Cornell University bird biologist John Fitzpatrick told AP. Keeping a species on the endangered list, he said, “keeps attention on it, keeps states thinking about managing habitat on the off chance it still exists.”

Craig Hilton-Taylor, an official at the International Union for Conservation of Nature, the leading authority on the status of wildlife, agreed. When a species is declared extinct, “[s]uddenly the [conservation] money is no longer there, and then suddenly you do drive it to extinction because you stop investing in it,” he said. 

But for many of the 23 species on this week’s hit list, that’s unlikely to be an issue: they were already in trouble when the Endangered Species Act was passed back in 1973. The kauai nukupuu, for example – another bird that was once endemic to a single Hawaiian island – hasn’t been seen since the 19th century.

“The Endangered Species Act has prevented the extinction of 99 [percent] of the plants and animals under its care, but sadly these species were extinct or nearly gone when they were listed,” Tierra Curry, a senior scientist at the Center for Biological Diversity, told Gizmodo. But, she added, “[w]e can’t let bureaucratic delays cause more extinctions” – some of the species on this week’s list, the Center for Biological Diversity has reported, went extinct due to hold-ups in the listing process to get them protected by the Endangered Species Act.

Nevertheless, despite the twin onslaughts of climate change and chronic underfunding, the Endangered Species Act has seen its share of success – some 54 species have left the endangered species list for much happier reasons since 1975.

“It’s a shame we didn’t get to [these] species in time,” extinction expert Stuart Pimm told AP. “[B]ut when we do, we are usually able to save species.”