if the world is "doomed" (noon Mayan calendar by the way) then what can "we" do about it? just live life and enjoy it until you can no more. worry about the things "you" can do something about and you'll enjoy life that much more, I promise.
Big flocks of birds? That's really not that unusual, I don't know about where you live but here the sky is black with them when they're migrating. We also get hundreds of vultures passing overhead at times. Birds move in large numbers. Really nothing to worry about.