Incubate vs broody duck

[Hope_nest_homesteadlady]

Hello. I have a broody call duck. She was originally sitting on 15 random unfertilized duck eggs plus a chicken egg or two. I have gradually taken some out of her nest. I want a couple more call ducks so I went ahead and ordered a couple hatching eggs but they are not cheap! I’m worried that I will put them under momma and she will break her broodiness before hatching day. Would it be more prudent to put them in my incubator and set under momma on hatching day if she is still on her nest?

 

[BoundlessLove]

How long has she been sitting on the current nest?