You can give a foster egg to a foster parent when you're confident that they'll take proper care of it. But it's best to have a substitute egg to give to the original parent so they don't realize that they've lost an egg. If you don't have a nonviable real egg to give them, you can use a fake egg instead.

Why were you planning to boil Quinn's eggs - was it to limit the cockatiel population or was there some other reason?

I originally just wanted to breed Cloudia and Moon but Bio started showing signs that he wanted to be a daddy so I just wanted him to foster one of Cloudia's eggs to relieve the need to be a father but I did want Quinn and Bio to at least have one of their own

I want to order the dummy eggs! How much do they cost?

The site isn't as easy to use as it used to be, but it looks like the price is $18.75 for 7 cockatiel-sized eggs. They're not cheap, but unless I look very carefully I can't tell the difference between the fakes and a real egg.

I did read a while ago in a post that the fake eggs are ever so slightly smaller than the real ones, but they don't notice the difference.

The size and shape of eggs varies from hen to hen and also within the same clutch. So it's normal for the eggs to not match each other precisely.

I think Bio has moved on from Quinn...but now he has found love with Marshmallow
Marshmallow is turning a year old this February! Bio just did heart wings to her and marshmallow always crouches but not in a mating position so when Bio comes to mate with her, Marahmallow will run up my arm and Bio would follow her up my arm and sing in my ear, and OUCH does that shriek hurt lol

I don't remember the family relationships in your flock. Is Bio related to Marshmallow?

I thought Bio was her father since he loved Quinn and you said Marshmallow lost her mother.

Georgie and Quinn were a married couple, they had 3 children names Marshmallow, Juno, and Willow
Bio had a little crush on Quinn so he wouldn't stop singing to her until she left so instead of him sitting there and sing for her, he would rather try to get Quinn's daughter lol

Your tiels' family history is like a saga, Baruch! You could write a novel about all that's going on in your flock, seriously!