LaFollette, Marcel C. (2008). Science on the air: Popularizers and personalities on radio and early television. Chicago: University of Chicago Press. [LaFollette, an archivist at the Smithsonian, draws deeply from correspondence between TWB and Austin H. Clark to provide the only extended published account I know of the Radio Nature League. Especially valuable for insight into TWB's personal feelings about the program.]
Goldthwaite, John (1996). The natural history of make-believe: A guide to the principal works of Britain, Europe, and America. New York: Oxford University Press. [Goldthwaite provides the only extended account I know of TWB's writing from a literary point of view. He praises TWB's simple prose style and places him squarely in the Uncle Remus tradition.]
Brooks, Paul (1980). Speaking for nature: How literary naturalists from Henry Thoreau to Rachel Carson have shaped America. Boston: Houghton Mifflin Co. [Brooks doesn't add any information unavailable elsewhere but his inclusion of TWB in the pantheon of great nature writers is encouraging.]