I've heard of/read about this happening with large migratory birds (storks and herons, for example) when flying into overhead powerlines or taking off after sitting on pylons.
Basically when an animal touches two powerlines an electrical circuit gets completed through the animal's body and the animal is zapped.
@birdsandbats
In the U.S., clear distances between wires are generally far apart enough that this would be uncommon. The picture shows wires that are 1-2 ft (30-60 cm) apart. Additionally, trees that could touch the wires are not allowed to be planted near utility poles, lowering the chance that animals could climb on to wires. Although, it is fairly common that large birds may get electrocuted.
Uncommon, but not unheard of... I've heard of Bald Eagles getting electrocuted here and there... I found a Great Horned Owl that had been electrocuted once.
