If you ever wanted a detailed account of the fate of the passenger pigeon, then A Feathered River Across the Sky, The Passenger Pigeon’s Flight to Extinction by Joel Greenberg is the book for which you’ve been searching. Mr. Greenberg is a research associate with the Field Museum and the Chicago Academy of Sciences Peggy Notebaert Nature Museum, and he attacks this topic with the attention to detail of a top-notch scientist. He begins the book by describing the almost unbelievable sizes of flocks in the 17th, 18th, and 19th centuries, and follows up with the equally unbelievable wastefulness of humans as they “harvested” this natural resource. Mr. Greenberg’s writing is pretty clinical, but he keeps things interesting by including interesting stories about individual characters in the passenger pigeon story (like Etta Wilson and William Butts Mershon). And I learned the origin of the term “stool pigeon”! Although it’s a very sad story about the extinction of a species, Mr. Greenberg does a good job of sharing an important lesson as he tries to focus attention on human-caused extinctions through this story and his Project Passenger Pigeon.