The eagle head was used by JG2. The rest of the art, as you named it ,was called the adler wings. These black painted areas can be noticed in pics of Wurgers of JG2,JG3, JG5 ,JG26 especially in the early period of Fw190 usage..The marking appeared because of an attempt at masking of the exhaust traces of the B4 fuel that made the Fw190 fuselages dirty simply.I think it was the main reason.