Wildlife Rehabilitation Center of Northern Utah
More than two dozen bald eagles suffering from tremors and paralysis were brought into the Wildlife Rehabilitation Center of Northern Utah during December. Most died. Wildlife experts now say it was due to West Nile virus, most likely contracted from eared grebe carcasses.

West Nile Virus Felled Bald Eagles in Utah: Wildlife Experts


A rash of bald eagle deaths in Utah over the past month is being attributed to West Nile virus, which experts believe they contracted from eating birds afflicted with the disease.

Hunters and farmers in northern and central Utah found nearly 30 listless eagles lying on the ground during December, the Los Angeles Times reported on December 28. The sight was heartbreaking, the Los Angeles Times said, as the paralyzed birds suffered seizures, in obvious pain, but with no known cause. They were taken to the Wildlife Rehabilitation Center of Northern Utah, where many died despite the experts’ best efforts.

"Every bird would come in more paralyzed than the one before it," said the center’s co-founder, Buz Marthaler, to the Los Angeles Times. "They couldn't move their legs. Their wings were weak. Their heads would jerk with tremors. It was difficult to watch."

As of mid-morning on New Year’s Eve, the total number of eagle fatalities stood at 27, 22 of them deceased when found in the wild, and six more that died while being treated at rehabilitation centers, the Utah Division of Wildlife Resources said in a statement. Five more were still being treated and appeared to be responding well, the division said.

Tests showed West Nile to be the cause, though officials were still confirming the source. Wildlife experts suspect the grebe, a long-necked, diving bird that stop at Great Salt Lake during its winter migration. One percent of the two million that pass through annually die of avian cholera, the division said. But the eagle deaths, plus inconclusive test results, caused them to analyze further. The eagles that died were all within flying distance of the lake, the division said.

"Every time grebes die, we send some of the dead birds to a laboratory for testing,” said Leslie McFarlane, wildlife disease coordinator for the Utah Division of Wildlife Resources, in the statement. “Usually, avian cholera jumps out as the cause of death. This year, though, the initial laboratory results were not as conclusive. That led us to believe that something else might have killed the grebes this year."

The division emphasized that the birds are not a vector for bringing West Nile to humans, since the mosquitos that transmit it are gone for the winter. Nevertheless they exhorted the public not to handle the birds. 

The bald eagle deaths, while distressing, do not put pressure on the numbers overall, McFarlane said, given that 750 to 1,200 of them visit Utah each winter. In addition, she said, the grebes’ annual migration is nearly complete, and almost all of them will be gone by the second week of January. 

"Even though it's difficult to watch eagles die, the deaths that have and still might occur won't affect the overall health of the bald eagle population that winters in Utah or the overall population in the United States,” she said in the statement. 

Nevertheless, that did not take away the sting of seeing the majestic birds die.

"It's just hard to have your national bird in your arms, going through seizures in a way it can't control—when you can see it's in pain but don't know what's happening to it," Marthaler told the Los Angeles Times. "As a human being, you just have problems with that. And when you lose one, it just grabs your heart."