What would the world sound like if we could climb inside the head of another animal? I went to the Olympic National Park some time ago with my wife and got some great recordings of humming bird vocalizations. The B&B we stayed at had feeders frequented by more humming birds than I’ve ever seen in one place. I never realized what feisty little creatures they are. I placed my handy Zoom H4n in the bushes just above the feeder and recorded while the little buggers fought and squabbled over the feeders and nearby flowers.
To us, their chirps all sound more or less the same, but, when slowed down, you can hear that these short high pitched bursts contain a lot more information than we perceive. Here’s a section of the same recording pithed down three octaves.
There’s a lot of interesting information out there on bird song, including this great podcast from Living on Earth.