[TowerTalk] Power lines, hawks, and fire ignition (slightly off-topic)

[Terry Conboy]

At 09:53 AM 2004-07-20, Bill VanAlstyne wrote:
>I couldn't help but wonder at this snippet from an AP newswire article in
>this morning's paper regarding how the Santa Clarita wildfire in California
>supposedly started: "[The wildfire] was ignited when a red-tailed hawk flew
>into a power line, was electrocuted and fell, burning, into brush."
>
>I know some of you guys on this list are extremely knowledgeable about the
>basic physics of electromagnetism. Could somebody please explain how a
>single high-tension AC wire can ignite a hawk? (Yuck.) Where does the
>current flow -- I mean, between what and what?

Usually this happens when the bird's wings make contact with both a phase 
conductor and something at ground potential (pole, tower).

Birds tend to avoid high voltage (> 57 kV) transmission lines because it 
zaps their feet when they land on the wires, but they don't seem to mind 12 
kV and lower.

Terry