I have one Lady Amherst pheasant male and tried to put him (6weeks old) with my Blue Laced Red Wyandottes chicks (4 weeks old and still bigger than him), and the chicks pecked at him until he was screaming. I don't think they (the chickens) like the nervousness that the pheasant brings to the bunch, because he is constantly pacing back and forth and walking on top of them with no regard for their space.
I ended up separating them until he matures a bit more and can protect himself from those mean roo's, or wanna-be roo's.
I have seen many people raise them together without any problems, but watch for the rooster chicks, they can be a bit prejudice of other species of animal, or anything that looks different.