Birds Migrate Using Sound

Migratory bird calls, which are very different from bird's normal songs, are used to track avian flight paths and numbers, according to a story in the 18 Spetember issue of The New York Times. They are high0pitched and clipped, each burst just a fraction of a second, and it took years for ornithologists at Cornell University to come up with what has been called "the Rosetta Stone of night calls", a link between the vocalizations and particular syrinxes behind them.

http://www.birds.cornell.edu/LabPrograms/Education/MNseminars.html

One can only hope the monkeys down below aren't listening to their music again...