"Fieldnotes," November 3rd & 4th, 2013: "Raptor Electrocution," by Jessica Lindsay. http://www.montananaturalist.org/
"Birds with large wingspans can close an electrical circuit easily by touching two components at once on poorly-configured electrical poles. Because raptors perch on poles to look down on fields in search of prey, this dangerous situation occurs frequently. Hundreds of thousands of birds die of electrocution each year. In some states, electrocution accounts for as much as 20% of bald eagle mortalities."