chasam Sofer YD 94
http://www.hebrewbooks.org/pdfpager.aspx?req=1839&pgnum=70
The case of the butter is the end of the teshuva and there the bird died so it doesnt have much bearing on this discussion but in the first paragraph brings from Pri megadim that live things arent maflit/ubolea.
(Technically he only says bolea)