FWIW...it takes about five years for a juvie Bald Eagle’s head and tail feathers to gradually turn white. During this time, Bald Eagles are distinguishable from the Golden Eagle in that the former has a more protruding head with a larger beak, straighter edged wings which are held flat (not slightly raised) and with a stiffer wing beat, and feathers which do not completely cover the legs.[5] The Bald Eagle is a large bird, with a body length of 70–102 centimeters (28–40 in), a wingspan of between 1.68 m (66 in) and 2.44 m (96 in), and a mass of 2.5–7 kilograms (5.5–15 lb);females are 25% larger.
The Wisconsin WDVA has him as a Bald Eagle: http://museum.dva.state.wi.us/Gal_Online_OldAbe7.asp
Maybe Old Abe was had an arrested development/ slow developer? ;D
Thanks for the clarification re: golden and bald eagles. I knew that juvenile balds have dark feathers on their heads and tails, but I did not know how long until they reached maturity. That explains a lot.