IME,partridge will do o.k in pheasant pens but need clipping the same as pheasants as they are ,as said ,very flighty .On a small shoot where time is valuable them mix them in to save having to visit two pens .You will need to keep back a pair of call birds though[before they are put in the release pen] and kept nearby in a smaller mesh topped pen .This can be in a clearing around the pen and surrounded with electric wire ,run off the pen .A wire bottem to any partidge pen is advisable to stop predators digging under .