This is available to buy fully rigged from turbosquid for $75, unfortunately its only for lightwave not cinema 4D.
Example of simple bird rig
This crow is £25 unrigged available for C4D - after storyboarding I will assess whether it's worth just buying the model and rigging it or go down the entirely hand drawn route for the raven. If it doesn't need to fly then I think almost sillhouetted or only the head crowing would be more efficient hand drawn. I initially had visions of the raven being used a transition flying in front of the camera but this could only be used once and I could possibly use that slow motion footage on google video as a basis to draw from.