I have created a model, rigged it(using rigify), and created several actions(animation clips) for it Blender. Everything seems to be fine. However, when I import the .blend to Unity I get a console warning that "Required human bone 'Head' not found". I know that there is a bone called "head" in my .blend. The animations work, except the head rotation does appear to not be deforming. Has anyone experienced this? Is this just a naming convention thing. Should I try to rename my "head" bone to "Head"? I just don't know the inner workings of the the import process well enough to know what to do.
I had this same problem so I went to configure it manually. When I selected the Head transform in Unity to assign it to the Avatar, it told me that the Head bone wasn't a child of the Chest bone. I changed this in Blender and when I came back, Mecanim accepted it.
The problem comes from the order you parented the bones. Make sure the Hip bone is not parented to the spine/upper legs. Instead the spine needs to be parented to the Hip (same goes for the upper legs), From there check the order of the nearby bones and correct the order you parented them.
After this Unity will be able to automatically recognize all the bones at the correct locations.
P.S for beginnings bone names are very important (Example) Hips, Spine, Left Upper Arm,Left Lower Arm,Left Hand. ect.
Select the joint as neck end where it is head