The Creative Commons and public domain contains a wealth of images, music and more. The images used in these show notes link back to the contributors.
Intro music: Kai Engel Walking Barefoot on Grass
Outro music: The United States Army Old Guard Fife and Drum Corps: United States National Anthem (The Star Spangled Banner)
Download Wake-Robin by John Burroughs in e-reader format at archive.org.
Click the links below for details about the bird vocalizations used in this episode from the Macaulay Library at the Cornell Lab of Ornithology: