Every fall, there is a flock (?) of grackles (I think) that comes through our neighborhood and just hangs out in the woods behind our house for a few weeks making grackle noises in the trees. Have you ever seen a flock of these birds? It's not just a dozen; it's more like a dozen dozen! They're black. And their noise isn't a melodious tweet-tweet; it's more like something you could use in your independent horror film to build tension as the lost hiker wends her way through the unfamiliar forest (total cliche, by the way - don't do the hiker thing in your movie). And it's weird because after about five minutes of the cacophony, you actually start to notice it and when you look to see where the noise is coming from, there are all these black birds everywhere - in the trees, in the sky, on the ground... It does not make you want to run outside. It's really creepy (you can use that in your film if you want).
But it's kind of cool, too.