Further ingo on genger for Budgie behaviour and when to separate

Question
Oh yes, I forgot to mention gender.  ALL of their cere are a light shade of blue and not distinctively different.  Orginally when I adopted the 1st one (green nominate) I thought he was 4-6months since he didn't have his cap stripes, but eye solid black, now that he has molted, I'm thinking is a dark-eyed and to forgo trying to guess age by the eye.  
Since he was the one regurgitating for the 2nd and I have seen him head bob to her, I'll say he's a male.  But, he has never warbled. And generally is pretty quiet and isn't very curious. He follows #2 around everywhere.
I tried for all males, but am now guessing the 2nd (16 weeks: white-based sky blue gray wing) is female as she doesn't head bob, or warble. Unless they both are females? Will one female regurgitate for another? She is more curious than the green nominate, but not as curious as our new 3rd. She generally is more bossy.  
The 3rd (10 weeks-olive based opaline )guessing male because he head bobs and warbles alot. He's very curious, friendly, and wants to be with the other two. He will defend himself, but does fly away if chased away. Guessing he is male.

Answer
Hi again, Gwen,

It is very difficult to guess a bird's age when a bird doesn't have an identifying leg band and when the signs of a young bird are gone.  It would be best to ask the person/place where you bought them from for their ages.  If the bird's have only had 1 molt, then they are 6-12 months old.  However, you may not know if this is their first molt(s).  Birds under 1 year of age molt twice their first year.  

Head bobbing in a young bird is usually a sign of begging to be fed, not part of a mating ritual.  If all their ceres are light blue, these birds could all be male, depending on their overall phenotype (coloration) and age.  I don't know what you mean by "warbling."  Yes, a female may regurgitate for another female, depending on their ages and relationship to each other.  

You really won't be able to sex these birds until they have molted at least once, perhaps twice, depending on their overall coloration.  You can't always depend on vocalness, curiosity, activity level to sex birds.  These traits should be taken into consideration with other things in order to try and guess gender.  If you want to be 100% positive right now, DNA sex them.

Chrys