Hello! We’ve just introduced a 4-6 month old budgie (Robin) to a 4 year old female budgie (P.S.), and although she isn’t being aggressive towards him, she is pretty obviously trying to mate with him, and I’m worried she’s stressing him out. We brought Robin home because P.S. was lonely after her cagemate passed, but she’s coming on a little strong. Should they be separated? Robin is also a very kind and friendly little bird, and we’d like to be able to train him in a stress-free environment (or as stress-free as possible). It seems like the two budgies have different needs.
I would just let the 2 birds stay together awhile longer. As long as there is no bullying or harm done. If she wants the young bird now, sooner or later she will succeed as it appears the 2 are going to be together. Maybe Robin is not even interested in her advances. I would let them stay together longer, as it is best they each at least have a member of their species to live with in addition to their humans.
I believe it's important you monitor the budgies carefully.
You certainly don't want any unwanted mating and need to ensure you discourage mating behavior.
If Robin generally wants to get away from P.S. and she continually pursues him, that is definitely going to stress him and isn't good for him emotionally.
Did you introduce the two in neutral territory?
If the behavior continues, then I'd suggest housing them separately and giving them supervised out-of-cage time together.
We'd love to see pictures of Robin and P.S. and your current cage set up.