I use a fan in both my duck and duck/chicken coop. and my dh does think I am nuts but it gets hot in there in summer and I have ALOT windows in my houses. Chickens especially are heat sensitive. Most important to have really good ventilation in our ducks/poultry coops.I just got off the phone with Metzer they didn't know anything about them being more heat sensitive. They were very nice but didn't have anything more to add.
I think in general there isn't really a right or wrong way to do things because it depends on so many variables. I agree my daughter and I are really enjoying learning and taking care of the baby ducks. Not sure she will remember it, she is pretty young but its something else we can enjoy together!
A fan for the ducks my DH would think I am nuts for sure!