West Nile To Blame For String Of Mysterious Bald Eagle Deaths

Dec 31, 2013

Utah wildlife officials say the mystery deaths of more than 25 bald eagles across the state have been solved. Laboratory results have confirmed that West Nile Virus was the cause of illness, ruling out lead, toxic chemicals and bacterial infections.

27 bald eagles have died across the state in the past month.
27 bald eagles have died across the state in the past month.
Credit Phil Douglass, Utah Division of Wildlife Resources

West Nile is typically seen during the summer when mosquito populations, which carry the virus, are high.

Assistant State Veterinarian Warren Hess said the eagles may have been sickened by eating the carcasses of eared grebes, a small water bird that lives on the Great Salt Lake. 

“By consuming those animals they got a high enough virus load that they were exposed directly to the virus rather than have an insect carry that virus,” Hess said.

Officials aren’t sure how the grebes got the virus or why the eagles have been more susceptible to the illness this year as opposed to years past. Hess said wildlife officials are looking into the possibility that the virus has mutated.

Eared gebes are suspected of carrying the virus.
Eared gebes are suspected of carrying the virus.
Credit Scott Root, Utah Division of Wildlife Resources

Five birds are currently in rehabilitation facilities. Hess said the lab results won’t change how the birds are cared for because there is no cure for the virus.

“What it’s doing to these birds is it’s attacking their central nervous system. Causing hemorrhages to occur in their brain and in their spinal cord and that hemorrhage destroys those nerve cells and if it gets bad enough the bird won’t recover,” Hess said.

The Utah Division of Wildlife Resources estimates that more than 2 million eared grebes stop at the Great Salt Lake during their winter migration. They are expected to leave the state in the next two weeks, at which time officials hope the bald eagle deaths will decline.

Eared grebes on a Utah waterway.
Eared grebes on a Utah waterway.
Credit Teresa Griffin, Utah Division of Wildlife Resources