On May 8, 1997, about 0951 eastern daylight time, a Piper PA-23-250, N520SM, collided with the ground during maneuvering flight at the Herlong Airport, Jacksonville, Florida. The airplane was operated by the pilot/owner under the provisions of Title 14 CFR Part 91, and visual flight rules. A flight plan was not filed for the personal flight. Visual meteorological conditions prevailed. The airline transport pilot received minor injuries, and the airplane was substantially damaged. Origination of the flight was at 0940 from Herlong Airport. According to the pilot, he was on a test flight to check the operation of his landing gear. The landing gear had been fixed the day before, after failing to retract completely. The pilot attempted to make a low pass over a grass strip between the runway and the maintenance building, so maintenance personnel could observe the landing gear doors. As he passed the building, a flock of egrets flew up into the aircraft. While attempting to avoid the birds, the pilot stated he struck a small hill. He then attempted a go around, but he was unable to maintain power due to propeller damage. The pilot then stated he decided to land gear-up in the overrun area straight ahead of him. Witnesses at the scene confirm that the pilot was making a low approach to check the operation of his landing gear. They stated a bird appeared to fly up in front of the airplane. The airplane then "dipped and impacted the ground". The airplane then "pulled back up". It impacted the ground a second time on the east end of the airport ground. According to the FAA inspector, the airplane was making a low approach to Herlong Airport when the pilot maneuvered the airplane to avoid a bird and collided with the ground. He stated the airplane became airborne again, but was not performing properly. The airplane impacted the ground again approximately 1 mile to the east of the airport, just short of the tree line.