SAN FRANCISCO (CN) — Conservationists faced off with the federal government in Zoom court Thursday in the latest chapter of a prolonged legal fight over whether the sage grouse, an iconic prairie bird with a waning population, deserves Endangered Species Act protection.

A subspecies of the greater sage grouse, the bi-state sage grouse can be found along the southwestern reaches of the California-Nevada border. The rangeland bird is known for its unique mating ritual, where males fan their feathers and puff up their chests in a distinctive dance to woo females.

Scientists say residential development, mining, and cattle grazing in the bird’s natural habitat have led to its precipitous population decline in recent decades.

The U.S. Fish and Wildlife Service agreed to list the bi-state sage grouse as threatened in 2013, a decision the agency has been trying to reverse since 2015. Environmental groups have taken the service and the U.S. Department of the Interior to court again and again trying to get it to reconsider, most recently in 2020 after the Trump administration announced its intention to withdraw the proposal.

The government claims its 2013 decision was made based on information the service now considers outdated.

In their latest lawsuit, Desert Survivors, WildEarth Guardians, Western Watersheds Project and the Center for Biological Diversity maintain that the sage grouse has lost over half of its historic population, and is at risk of falling below the minimum number of birds needed to evade extinction.

Fish and Wildlife argues the number of birds needed to maintain an effective population lies somewhere between 50 and 5,000, without setting an exact threshold. Instead, it claims the population is viable because it remains above 50.

It further contends there is no “universal magic number” and that an effective population size for the species is “approximately 330 to 661 sage grouse, below the 5,000 individual threshold recommended by some researchers, but above the 50 individual threshold.”

Meanwhile, the groups have advocated for a commonly accepted population viability threshold of 500 minimum.

“The service has identified two thresholds without picking one of them, one of which the species is below, and then has also again not provided us with a meaningful threshold. The service’s analysis is insufficient here because it doesn’t provide a reason to dismiss the 500 estimate,” Stanford law student Daniel Ahrens argued on behalf of the environment groups at a video hearing before U.S. District Judge Jacqueline Scott Corley. “The reason why we’re here is the species is at risk. We are trying to get protections for it before it becomes extirpated.”

Corley, a former U.S. magistrate judge newly confirmed to the Northern District bench, called the effective population size “the heart of the matter” for a potentially threatened species. She asked the service to explain itself.

Representing the service, Justice Department attorney Michelle Spatz said there is no required number since it goes through natural population cycles in response to habitat conditions that compensate for each other over time.

“This is a fluctuating population. It has been historically, and we expect it to be in the future,” she said.

Corley asked whether the service had considered the ramifications of California wildfires and drought. “For those of us in California, drought and wildfire are certainties that continue to occur. I wish we’d have no more drought but that seems unlikely. So where did the service take that into account?”

Spatz said there isn’t enough evidence to conclude whether current California drought conditions will have a serious effect on the sage-grouse population.

“Obviously wildfire and drought have always been here and always will be,” Spatz said. “The service does not have enough information to know whether drought is going to continue forever, and based on history, it would not. There are droughts, and droughts go away. Based on the evidence in front of the service and the history of the population of the bird, it’s expected that it will go back up.”

But she said the service would be willing to reconsider its decision if the drought persists. “That would be a decision based on different evidence later on. But the evidence now is there is no basis to make that kind of speculative conclusion that this [population] won’t go back up and down as it always has.”

Corley remarked: “That’s a little tough for someone sitting in California.”

Ahrens said the drought is likely to continue, and will only increase in frequency and severity due to climate change. “The service itself also notes, tellingly, that there are no conservation actions that can protect the bi-state sage-grouse from climate change. It’s an unprotectable threat. It’s very clear this evidence was before the service and they have failed to appropriately consider and assess this threat.”

Spatz told Corley the government committed no clear error in withdrawing its 2013 proposal. “Particular deference should be afforded to the agency’s judgment and scientific expertise,” she said.

Before taking the arguments under submission, Corley said she would “try her best” in adjudicating her first Endangered Species Act case. “I have a lot to think about. It’s complicated. It’s kind of like a patent case — it seems crazy that they’re asking a federal judge to resolve this,” she joked.