At almost every mediaeval banquet there would have been an 'illusion' or centrepiece. This was quite often a confectionary boat, marchepain (marzipain) models of animals or birds, "entrails" - a string of dried & fresh fruits covered in batter and baked, anything edible that was made to look like something else.... (like those terribly annoying books that are really a tin of biscuits) to create interest and amusement. The pie was probably baked blind (pie crust baked with a filling that was a bag of washed pebbles, anything to give the impression it was a whole pie, and to stop the pastry from rising too much. The birds were probably inserted into the dish, the hardened crust placed over them and then it was served. The birds would not be harmed other than a little overcrowding in a dark place, but would still be alive when the pie crust was cut or broken.

LTS