The feedback on what makes the white wing bar effect (prior to posting the fight shots) argues for (a) extreme wear of the coverts or (b) molting of the coverts. Neither commentator points to partial leucism as an explanation.
The bird was found on Duxbury Beach (MA)in the cove area south of "High Pines". The first 3 pix were taken 8/12/09 and the flight shots on 8/15/09. It was seen again on 8/16 on the ocean beach opposite Plum Hills.