CASPER, Wyo. - PacifiCorp and Exxon Mobil Corp. face federal charges of killing scores of migratory birds in Wyoming.

The companies are charged, in separate cases, with violating federal laws protecting birds, according to documents filed last week in U.S. District Court in Cheyenne. The charges are all misdemeanors.

PacifiCorp, which does business in Wyoming as Rocky Mountain Power, is charged in the deaths of 38 golden eagles at power poles in six counties from December 2007 to February 2009.

ExxonMobil faces charges in the deaths of at least 64 birds, including ducks, grebes, passerines and shore birds.

Hydrocarbon exposure

Court records say the birds died after contact with hydrocarbons in an ExxonMobil disposal facility and evaporation ponds in Sublette and Lincoln counties.

Both companies say they are working with federal officials to resolve the complaints.

Dave Kubichek, assistant U.S. attorney in Wyoming, said the ExxonMobil case is part of a group of similar prosecutions involving company operations in other states. He said the cases have been consolidated.

U.S. District Judge Clarence Brimmer in Cheyenne signed an order on Wednesday transferring the case to federal court in Colorado for a guilty plea and sentencing, according to the court docket.

A spokeswoman for ExxonMobil issued a statement saying the company has worked in good faith with the U.S. Department of Justice and the U.S. Fish and Wildlife Service to resolve issues regarding protection of water birds on company property.

Bird deterrence

"The company has a long-standing water-bird protection program that focuses on deterring birds from landing in water on company property," Margaret Ross said from ExxonMobil headquarters in Houston. "This program includes various technologies for bird deterrence."

Ross said ExxonMobil has extensive operations across the U.S. that deal with millions of birds. "Our upstream operations have reported events involving fewer than 100 birds over the past six years," she said.

PacifiCorp is scheduled to appear before U.S. Magistrate Judge Michael Shickich in Casper on July 10 to enter a change of plea.

"We believe we've reached a resolution with the U.S. attorney and the Fish and Wildlife Service subject to approval by the court," Pacificorp spokeswoman Margaret Oler said.