That is a nice sized pen to begin with and making it larger is a good idea for pheasants.My smallest flight is 8ft high, 20ft long by 5ft wide making 100sq ft of floor space and it is too small for keeping pheasants in. I'll be expanding the pen 10ft wider so it'll be 300sq ft for a trio of pheasants. If the ceiling is too low the birds hit it if they fly up alarmed and injure themselves, sometimes even breaking their own neck so I would suggest a minimum hight of 8 feet, then you can keep doves as well if you decide to later.
-Stephen
We try to keep our pens for the chickens at least tall enough to walk in so we don't have
to duck down. We have breeding groups of 5-8 birds for some breeds but for smaller
groups we use smaller runs but still tall enough to walk in. It's rather hard to catch birds
in low pens.
