A female spruce grouse isn't something one normally expects to find on one's third floor balcony ... they're not notable for being high fliers. Most likely she took off from somewhere on the far side of the courtyard ... the slope is steep enough that the top of it isn't very far below me (my building marks the downslope boundary of the courtyard). She was standing and took a couple of steps when I first checked so I don't think she's injured, just a little disoriented and possibly confused by the bars of the balcony railing. Their spacing is more than wide enough for her to get through but it just may take her a while to figure that out. Will keep an eye on her and do something about taking her down to ground level later if she doesn't manage it herself.
Edited to add: went back to the balcony to check after posting this and she's scooched under the railing and perched on the very edge of the concrete, so she's clued in and able to take off whenever she wants.
Second edit: I just got to see her take flight so all is good. :-) She explored her way right to the very corner of the balcony and got under the railing again there so that she could get her wings spread for flight before launching. That was my only concern about her being able to get off the balcony herself ... grouse aren't drop and then flap birds, they need to be able to spread their wings and do a downflap first and that wasn't going to be possible in the mid-balcony spot where she had originally got under the railing unless she leaned out far enough to overbalance and fall.