From a birder's point of view having a quality phone birding field guide is a basic everyday tool that every serious and beginning birder has to have. As field guides to the Sibley guides are simply superb. David Sibley brings the unusual convergence of talents to the table. He is a world renowned birder, a superb artist, and a very good writer. Owning this app is a no-brainer for any aspiring North American birder.