Solomon and the Hoopoe
This is fascinating... The hoopoe bird shows up in several grimoires as an acceptable sacrifice to angels and spirits. Reading this article, we get an idea why::
Apparently, the hoopoe was Solomon's messenger bird. If that was its function (either in myth or reality) it would explain why a hoopoe would be used as a sacrifice in magick. The spirit of the bird would carry the prayers and invocations to the other side, and/or carry messages from the other side back to the conjuror.