At 1253 Central time, the airplane was substantially damaged on impacting several birds. The pilot, co-pilot and three passengers were not injured. Instrument conditions prevailed. The pilot reported he was descending through about 4000 feet in IMC, when he saw a black flash, and heard and felt a “tremendous thud.” Both pilots reported there was no change in engine performance, pressurization or flight control feel. After assessing the damage the flight crew decided to return and landed uneventfully about 25 minutes later. Examination revealed substantial damage to the left wing spar and left wing leading edge outboard of the left engine. Bird residue and feathers were observed near the damaged area of the left wing. Additional damage and bird residue was noted on the vertical fin of the tail section.
