https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/comments/751049133


There is a xml missing.


Fix
The fix is quite simple to perform while Fluffy works on fixing the actual steam release.
It seems the release was a bit borked, one of the necessary files is missing.
For the folks that want to fix it themselves, it is quite simple.

The missing "FertilitySource" found in this file: https://github.com/fluffy-mods/BirdsAndBees/blob/1.1/Defs/BodyPartTagDefs/FertilitySource.xml
Notice it is located in "Defs/BodyPartTagDefs/FertilitySource.xml"

If you go to this mod's folder, located at "YOUR_STEAM_FOLDER\steamapps\workshop\content\294100\751049133" and then go inside either the 1.0 or 1.1 folder, then Defs, you'll see there is no BodyPartTagDefs folder at all. Simply create said folder and add the file I linked (you can right click on "Raw" and "Save as...", or manually create it). Your game should load normally then.