If one of your patrons wants to “hear” the sound of a particular bird and you happen to be the librarian at the reference desk, when this uncommon question is asked, don’t panic, just refer him to the Cornell Lab of Ornithology – Macaulay Library.
"The Macaulay Library is the world's largest archive of animal sounds. We have more than 160,000 recordings of 67 percent of the world's birds, and rapidly increasing holdings of insects, fish, frogs, and mammals." Macaulay Library also has 700 hours of video archive representing 3,000 species of birds. You can watch and listen to all animal behavior recordings for free, and fee is charged for preparation (staff time) of recordings for delivery. Found via Librarians' Internet Index: New This Week