A whooping crane found shot this month has been euthanized after his condition deteriorated beyond the point of rehabilitation, wildlife authorities said.
Wednesday's death in Louisiana means at least 20 whooping cranes have been shot to death since 2001, a serious dent for the endangered species of 600 birds. A few birds die each year during cross-continent migrations, killed by predators or by crashing into power lines. But the steady number of fatal shootings has frustrated environmental advocates.
Decades of research and millions of dollars have been spent by government and private organizations to revive the species, whose population shrank to 23 in 1954, according to the U.S. Fish and Wildlife Service.
Two days after the crane was found alongside a fatally shot female, the male underwent surgery to repair a fractured wing at the Louisiana State University School of Veterinary Medicine.
The school had reported that the bird was recovering well until his condition took a turn for the worse Tuesday.
"The crane's condition ... weakened to the point that any efforts to try to revive him would have exacerbated his condition," the school said Wednesday.
A $15,000 reward has been offered for tips that lead to a conviction in the case.
Louisiana added a whooping crane population in 2011, and it now stands at 31. The dead birds, ages 4 and 3, were the state's oldest couple. They were expected to produce a chick within a year or two. Cranes mate for life.
The 5-foot-tall birds, which typically live for at least two decades, neared extinction in the early 20th century. Today's 600 whooping cranes are spread among three main flocks in North America.
They are protected under the Endangered Species Act and the Migratory Bird Treaty Act. Shooting a whooping crane can lead to a $100,000 fine and a year in federal prison.