Mandarins: will they come back or will they be gone forever?

[raingarden]

Ducks are not very good at expressing gratitude for everything we do for them. So, it's nice when they choose to stay and are not forced to stay.

 

[MGG]

I agree with The Phantom, I highly doubt they'd ever stay in there. If given the opportunity to fly away they will, and unless raised there from day olds and really bonded with either you or the other ducks, they'd probably never come back if they flew off.
I'd never have any in an uncovered pen.