travel doc authoritative info

According to Rebecca at AirCanada, a photocopy of my birth certificate
should be fine.  She also suggested a copy of my voter registration,
because only citizens can vote and it would have my polling place on it.
She said that they used to accept voter registrations, but then they
inexplicably started denying them as valid ID, and just recently they
started accepting them again on a trial basis.

It's worth noting, I think, that neither the AirCanada website nor the
U.S. State Department travel site mentions the acceptability of the
photocopied birth cert.  And yet, according to at least one person in the
know, they should be cool.

Thanks to everyone who replied with helpful suggestions-

-jared