My explanation of Jesus' saying in Luke 17:37 will have to be updated in the light of a 2003 article written by John Topel for Biblica. While my explanation that the "when" and "where" of the Parousia in the rebuttal of Jesus to the Pharisee's question can be admitted, it lacks one element which the saying about the vultures and the carrion indicate. According to Topel:
Vultures arrive at the scene after death has taken place, or the animal is already irreversibly dying, is already "dead meat." Vultures are a post factum sign that an event (an animal's death) has already occurred. In that case, the proverb about vultures fits Jesus' purposes perfectly in Luke 17,20-37. Jesus has responded to the Pharisees that the final Reign of God will not come with advance signs subject to human observation (17,20)
Thus, when the signs of the Parousia do come, human reaction to it will already be so late that no one can prepare for the Parousia itself.
Topel's article also comes with a section on eagles and vultures that is very informative. 
__________________
Don't curse the darkness, light a fire. Don't wait for the sunrise. Walk towards the dawn.
