Add a "reverb" effect to simulate the sound bouncing off distant trees.
: For clearer, daytime forest sounds that you can later "distort" for a creepy effect, Deti Online has excellent categorized clips of streams and summer forests.
: The "quiet" before a storm where all birds stop singing.
: If you need the foundation (wind, rustling leaves, night birds), the Forest Sounds app on Google Play provides high-quality 3D surround sound effects that set the perfect stage for a supernatural encounter.