Wildlife advocates have begun legal proceedings against U.S. officials for allegedly failing to protect a ground-dwelling bird species that's seen its habitat shrink due to farming and energy exploration.
The lesser-prairie chicken roams portions of New Mexico, Colorado, Texas, Oklahoma and Kansas.
It was listed as a federally-threatened species in 2014. That was reversed two years later under court order.
The Center for Biological Diversity and two other groups on Thursday filed notice they intend to sue the U.S. Department of Interior for not acting on their 2016 petition to restore protections.
Aerial surveys show lesser-prairie chicken populations trending upward in recent years and topping 38,000 birds in 2018. But the survey also raised concerns that drought over portions of the birds' range could lead to a downturn in 2019.