Would birders rent books?
In its selection of nonfiction paperback titles, I don't see a section for nature or another birding-related topic; do you see one?
The audiobook selection does include a nature section, but it contains more titles related to pets than wildlife. Fortunately, it does offer various birdsong collections and a few birding-specific audiobooks.
Do you know of any birders who've used Booksfree.com? Would it serve the company to beef up its offerings?