Bird sounds have something special about them.
Rachel Carson's Silent Spring, one of the works that helped propel the modern environmental movement, took its name from the unnerving quiet that came from DDT's devastating impact on bird populations. An art exhibit in Sydney, Australia, plays the songs of birds that used to inhabit the city. Then, on a personal level, the song or call of a species I am familiar with is enough to give me a smile.
Bird sounds are also important for identification purposes, and the Cornell Lab of Ornithology has a great collection of songs and calls from North American species. The lab is now making the complete set available for purchase as MP3 files. A smaller, less expensive collection is also available. Both can be purchased for a limited time at a discounted rate. For more information, check out this entry from the lab's Round Robin blog.
Bird sounds occupy an important place in our world, and getting to know them makes their impact all the more meaningful.