 They represent demon powers. I can prove that if you look in chapter 13, verse 19. Look at it again. He's saying here that it's the power of Satan. And when anyone heareth the word of the kingdom and understandeth it not, then cometh the wicked one and catcheth away that which was sown in his heart. These birds that catch away the seed illustrate the devil. Now put this verse in your margin. I gave you this before, but this clears it up.