I would be extremely careful with this. While it may work in some cases, it typically doesn't work. Pheasants cannot free range with chickens, they also require separate feed. A pheasant pen should be very roomy and I've seen many a pheasant actually attacked by chickens. If you have a HUGE coop, it may work, but it is generally a case by case thing. What works for one, may not work for others.
Pheasants needs are just too different from a chickens for them to live a happy life coexisting.
I've never been a fan with the square feet per bird method, is more used by those in production. I would recommend - again, depending on the species - that an aviary 8x12 or 10x10 would be the minimum for a pair of typical sized species (Ringneck, Silver, Swinhoe, Amherst); when planted and with lots of enrichment items, smaller sizes such as 8x8 can be used for species such as Golden or Edwards.
If you can afford it, please provide as much space as you can. Include in the aviary small trees and shrubs, rocks, logs, grass tufts and other items to simulate as much a natural environment as possible. Bare runs are not suited for pheasants and will fare much better if treated as close to the wild species they actually are.
Thank you, basically a coworker of my wifes asked if we would be able to raise them for him.
I am not really interested in have pheasants, so I think I will just 86 the whole idea now. I am not very comfortable having mixed species in the same house. I would rather just have the chooks. I also don't really agree with the sq ft per bird method, however I will use it as a baseline and usualy increase the space requirment of my birds so they aren't crowded. Thanks for the info -Bill