Including link: https://blogs.loc.gov/

"I thought this was simply a  nursery rhyme:  how could one bake living birds in a pie? I discovered that royalty and the upper class, as a way to impress guests, would order their cooks to create elaborate pies which contained living animals. The recipe for Live Birds in a Pie from the Accomplisht Cook (1671) is a later example of such a recipe that contained both live birds and frogs."
https://blogs.loc.gov/inside_adams/2011/11/pie%e2%80%a2ology-a-full-filling-story/#:~:text=I%20thought%20this,birds%20and%20frogs.