The coastal black-throated green warbler was one of the first birds that Will Harlan learned to identify growing up, and he later taught it to his children.

“It is stunningly beautiful. This bright, vibrant yellow head is visible as it flashes through the forest,” said Harlan, who lives in North Carolina. “It also has this beautiful song, a really recognizable song. Its song used to fill the forests, and now those forests are silent.”

He rarely, if ever, hears the warbler’s song anymore. The coastal species’ population has fallen by 90% over the past few decades, with fewer than 2,000 birds remaining.

A lawsuit filed this week claims the federal government has failed to protect the species. The Center for Biological Diversity sued the U.S. Fish and Wildlife Service for not acting on the nonprofit’s 2023 petition to list the warblers as federally endangered.

“We can't wait any longer. This bird, frankly, can't wait any longer,” said Harlan, Southeast director and senior scientist with the center. "It urgently needs to be listed and it's running out of time.”

The coastal birds, known as Wayne’s warblers, are a genetically distinct subspecies of black-throated green warblers. They stay close to the coast, dwelling solely in the wetland forests of Virginia and the Carolinas.

It’s “one of the country’s rarest and most imperiled bird subspecies,” the nonprofit writes in its legal complaint, filed in the District of Columbia’s District Court. The group claims the government violated the Endangered Species Act by failing to timely respond to its prior request.

The Fish and Wildlife Service declined to comment on the litigation.

The federal listing process begins when members of the public petition for a specific animal to be reviewed. The Fish and Wildlife Service then uses “the best scientific and commercial data available” to assess whether listing is appropriate, the agency states on its website.

Some species are deemed “threatened,” meaning they’re likely to become endangered within the foreseeable future. Endangered animals are considered at risk of extinction.