http://boards.sportslogos.net/topic/92155-origin-of-bills-charging-logo/
From the above; read more at link:
Today's Buffalo News has an article noting the passing of Stevens Wright, credited with creating the Bills' charging bison logo which debuted in 1974. The article says Wright, who had worked as a free-lance artist for NFL Properties, came up with the logo on his own.
However, Howard University, whose nickname is the Bison and whose logo is virtually identical to the Bills', claim the logo was created for them by a Howard art major in the 60s. Because they didn't copyright their logo, the Bills were able to take it for themselves.