I have a family of Barn Owls who frequent my redwood trees every night - if I was smart, I would record their calls. The first time I heard the mom screeching I thought the devil had me. Would make for a great Halloween sound effect. LOLI'm a firm believer in owls as ambience, be it the booming hoot of the Great Horned Owl, the eerie whinny of the Screech Owl, the human-like shriek of the Barn Owl or the hooting laughter of the Barred Owl.
And no, I did not get the Screech and the Barn mixed up. The Screech owl has a whistling whinny, common in horror films. It doesn't screech much at all. The Barn owl sounds like a startled old woman.
In fact, if you wanna hear a Barn Owl, watch "My Cousin Vinny". A Screech Owl was used for the close-up, but a Barn Owl's call was used for the audio because the filmakers quickly realized that the Screech Owl doesn't quite live up to it's name.
For our British and Irish friends, there's the mournful "Twee-whit Twee-whoo" of the Tawny Owl.
Get to know your owls. Use a local call in your graveyard as the predominant sound. Tricksters will stop and look for the bird - honest.