The U.S. Fish and Wildlife Service acted illegally in 2015 when it denied Endangered Species Act protection for a distinct population of bi-state sage grouse in California and Nevada, a federal judge ruled. U.S. District Chief Magistrate Judge Joseph Spero in San Francisco said in an 85-page opinion that the agency ignored its own best scientific evidence when it reversed course three years ago on its 2013 proposal to declare the bird threatened.The bi-state sage grouse found along the California-Nevada border in the Mono Basin along the Sierra’s eastern front is related to but distinct from the greater sage grouse, which lives in a dozen western states and is at the center of a disputed Trump administration plan to roll back protections adopted under President Obama.The judge said the service wrongly concluded voluntary conservation measures in the works were legally adequate to stem the loss of bi-state grouse habitat resulting from urban sprawl, livestock grazing, wildfires, invasive plants, mining and other development.