SALT LAKE CITY (AP) — Testing has confirmed that more than 50 bald eagles died in Utah after scavenging on dead grebes that had the West Nile virus, the National Wildlife Health Center said.
Wildlife officials earlier confirmed the virus caused the eagle die-off that began Dec. 1 and speculated dead migrating aquatic birds such as grebes were the culprit.
The center announced Friday that follow-up testing on dead Utah grebes showed they had the virus, the first time it has been seen in them. They tested negative for lead, avian influenza and other possible causes of death. Up to 20,000 of the grebes died.
West Nile virus, which is spread by mosquitoes, usually infects birds during warmer months.
The eagle death toll has climbed to 54, with four birds currently in rehabilitation, said Leslie McFarlane, wildlife disease specialist for the Utah Division of Wildlife Resources.
Grebes have since migrated out of the state, and reports of sick eagles have “dramatically decreased,” McFarlane told The Salt Lake Tribune (http://bit.ly/1dIeNpH ).
But the number of eagle carcasses being found is increasing, she said, and the trend may continue as snow melts.
Eared grebes gather on the Great Salt Lake in large numbers each fall before continuing south. While Utah has a small population of resident bald eagles, their numbers are bolstered by up to 1,200 migrating eagles during some winters.
Wildlife officials said that during the winter, the eagles get most of their food by eating dead animals, such as grebes.
The dead eagles have turned up in northern and central Utah. All were either dead or were ill and later died during treatment.
The eagles displayed similar symptoms, including head tremors, signs of seizures, weakness in legs and feet and a paralysis of the bird’s wings.
Information from: The Salt Lake Tribune, http://www.sltrib.com