As a descent was initiated 10 to 12 miles northeast of the destination airport, a "loud bang" was heard by both the private pilot and the flight instructor, and they felt the airplane, a Cessna 172P, shake. Both pilots agreed that the engine gauges and flight instruments indicated normal operation, and no changes to the flight characteristics were noted. The strobe lights and navigation lights were on before the "loud bang" was heard; however, they had not yet turned on the landing lights. Upon landing and further examination of the airplane, blood and feathers were observed on the right wing, and substantial damage was incurred to the main spar and leading edge of the right wing.