I had for budgies living in one cage. 1 was only 3 months old and was a boy and and one was about 6 months old and was a girl( i was going to breed them in about 9 months), and my other 2 (boy and girl) were both about 1-2 years old. I was keeping them together for about a week while i was building a nest box. I moved my older pair out last week and now they have 3 eggs. But now my 6 months old girl, who isn't in breeding condition is making a nest in sawdust on the bottom of the cage. She is sitting there plucking out her feathers and putting them around her and is chewing up the sawdust. I think she might have mated with my older male, what should i do!

Have you got another cage you can put her in with nothing on the floor of it ( the sawdust is enticing her to nest )........and lots of toys to distract the nesting behaviour ?

Was the nestbox in the large cage with all of them at any time at all ?