Bald Eagles
© Scott G Winterton/Deseret NewsBald eagles are perched at Farmington Bay Wildlife Management Area Friday, Dec. 20, 2013. Eagles are turning up dead and officials are working to find out the cause.
Salt Lake City - More than 12 bald eagles have died in Utah since the beginning of December, and wildlife experts don't know why.

"We've never had this many birds come in, of one species, coming in as quickly and in this short of time span and having them all die," said DaLyn Erickson-Marthaler, executive director of the Wildlife Rehabilitation Center of Northern Utah.

Since Dec. 1, at least 13 majestic bald eagles have died. The latest, a 1-year-old female, died Saturday, Dec. 21. She was discovered last week near Centerville by a jogger and was brought to the rehabilitation center in Ogden.

"It's frustrating and heartbreaking," said Leslie McFarlane, Division of Wildlife Resources wildlife disease coordinator. "It's really hard because you want to be able to do something right now and we just can't."

About all anyone knows so far is that all of the eagles were experiencing the same symptoms.

"They were showing signs of body tremors, they would have seizures, they appeared to be paralyzed and they had weakness in their feet and in their legs," Erickson-Marthaler said. "It's hard to watch. It's really frustrating to not be able to know what we're treating, what we're seeing, if we can even treat it at all."

Now is the time of year when eagles are seen often in northern Utah. They migrate here from other states and linger near the marshes of the Great Salt Lake, where there are plenty of carp to eat in freshwater bays. The Division of Wildlife Resources conducts annual counts, and the numbers range between 700 and 1,200.

Adding to the concern, the dead birds weren't discovered in just one spot, they were found in five counties: Box Elder, Davis, Tooele, Utah and Weber.

"Usually if you have something, say like a poisoning or something like that, usually you find them in small geographical areas or something along those lines," McFarlane said.

The dead eagles were sent to labs for tests, but results may not be back until the end of the year.

"Even then, even when we do find out what it is, it may be something that we can do nothing about," McFarlane said.

Wildlife officials said none of the eagles were shot, and there are no signs of anything malicious going on.

DWR officials are asking anyone who sees a dead bird not to pick them up, touch them or carry them around. The best thing to do is call them, and they will send an expert to pick up the bird.