general details on sexing weiros/cockatiels

Question
Hi Chrys,
I have two cockatiels,which I would like to determine their sex.
One is darkish grey,Yellow head with red cheeks.
Other one is light grey White head & face with no colour on it.
Secondly, they both talk.  Do only MALES talk (in which case I obviously know that BOTH are males, or do both sexes talk.  Is there any 'general' principle to determine what sex ANY cockatiel is?.
Regards Peter
Secondly

Answer
Hi, Peter.

I'd have to see a photo of the 2 birds in order to try and sex them visually.  With tiels, yes, usually only males learn to mimic.  Females chirp, but males have a beautiful song and are usually the more vocal of the 2 sexes.

Tiels can usually be sexed visually if you know what to look for.  However, some color mutations, such as pieds, or other multiple color mutations, can be very difficult to sex visually.  In these cases, taking colors, behavior, and vocal ability can help to narrow down the sex of a bird.  

If you can send a photo(s), let me know and I'll provide an E-Mail address.

Chrys