The following flying creatures must be found for the Room Of Rewards:
Bats: Can be found below the Stone Bridge. Go to the Stone Bridge and light 
all the torches with Incendio. Then, climb down the pipe shown and maneuver 
your way to the bottom. You will discover the bats.
Crows: Can be found at the Stone Circle.
Doves: Can be found at the bridge at the Viaduct.
Pixies: Can be found in a desk in the Defense Against The Dark Arts room.
Seagulls: Can be found at the boathouse.