WordNet (r) 3.0 (2006):

scarer
    n 1: an effigy in the shape of a man to frighten birds away from
         seeds [syn: scarecrow, straw man, strawman, bird-
         scarer, scarer]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "scarer":
   Dracula, Frankenstein, Wolf-man, bogey, bogeyman, bugaboo, bugbear,
   fee-faw-fum, frightener, ghost, ghoul, hobgoblin, holy terror,
   horror, incubus, monster, nightmare, ogre, ogress, phantom,
   revenant, scarebabe, scarecrow, specter, succubus, terror, vampire,
   werewolf