Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Serves as a useful complement to field guides

This handy little item has two virtues that complement standard field guides like Sibley or National Geographic. First, you can unobtrusively take it with you everywhere-- on a walk around the neighborhood, on a bike ride, to a BBQ, you name it. Second, because it contains only around 140 species, I find that I can identify an unfamiliar Bay Area bird more quickly than I can using Sibley or National Geo. And, because it's laminated plastic, it's holding up quite well to being repeatedly stuffed into some pocket or other. It's certainly not a substitute for the standard, comprehensive guides, but for a few bucks it serves a useful function.