It's two great tools in one field friendly package! Get this exceptional value that includes the Birds of Wisconsin Field Guide and the Birds of Wisconsin Audio CDs with a 36 page booklet. The book and CDs are designed for each other. The track number at the bottom of each page in the field guide directs you to the correct CD track. Likewise, the audio CD index references the field guide. Make bird watching more enjoyable, simple and informative with this amazing set.