According to the pilot, the airplane was at 1,000 feet, airspeed about 100 knots, and he was following tower instructions to enter a right downwind for the runway. Approaching the downwind leg, he saw a large black bird and commented to his passengers that they had to keep an eye on it in case they needed to maneuver. The pilot continued toward the airport, looking for traffic and birds, and within a few seconds the airplane was very close to the bird. The pilot descended the airplane to where he thought it would pass overhead, but the bird then dove at the last second and the pilot heard a "thud" on the cabin roof. There were no other indications of impact, and the pilot continued a "normal" right base, a right turn to final, and landing. Once back at his hangar, the pilot noticed the substantial damage to the left ruddervator. A feather retrieved from the ruddervator impact site was examined "whole feather" and microscopically, and was determined to be from a black vulture (coragyps atratus) with an average weight about 4.7 pounds.