found those here

...including this:"The British Library has a Listen to nature website with 400 audio extracts including many interesting bird sounds. Check out Nightingale (a 1910 recording, "the first published recording of a bird") under "Wrens, Chats and Thrushes," where you will also find a very nice Musician Wren. On the site is Jeffrey Boswall's Language of Birds, "an introduction to how, why, and when birds communicate."