If you draw your bow and fire arrows at the dragon you will depending on where you strike be granted with a different reward:
Shoot the body - Dinraal's Scale, Farrosh's Scale, Naydra's Scale.
Shoot the horns - Shard of Dinraal's Horn, Shard of Farrosh's Horn, Shard of Naydra's Horn.
Shoot the claws - Dinraal's Claw, Farrosh's Claw, Naydra's Claw.
Shoot the fangs - Shard of Dinraal's Fang, Shardof Farrosh's Fang, Shard of Naydra's Fang.