The semen of the Northern goshawk.
I have been working on preserving the semen of the Northern goshawk for over 10 years. I freeze it in frozen straws in liquid nitrogen. This keeps for decades. I succeeded this year with high cell survivals of over 90% and a fertile egg in a single egg clutch. I now have a tool to offer to conservationists, if captive breeding ever becomes possible. This can be used for other endangered birds. See CryoSaps.com.
It took me a while working backwards to see they were talking about tree sap as a sperm medium. Wow, that caught me off guard. The maple syrup market will want to play down this association, I am guessing.