This is an interesting subject. Please keep it going for me! I currently own a pair of call ducks.... After their spring molt, she started to behave differently than normal. They have started breeding again and she is now laying eggs in various places in my flower beds. She is constantly in search of some secluded area to lay. Her very first egg this year was a soft shell end and I knew it wasn't going to be viable. So far, she has laid 5 eggs. Two were found in one spot, so I put all of them there. Hoping she will go broody in the near future.
Meanwhile, I have a very stubborn broody bantam hen that I have secluded and put 2 of the duck eggs under her today (17th). Hoping for the best...
I will be watching this thread for more information as it develops!
I conclude that a chicken can/will hatch out a ducks egg...
Now I'm off to research some more.