From Belize to Brazil, the forests of the American neotropics are home to an astonishing array of birds--over 3,700 different species, or nearly 40 percent of all the birds on earth. Because of this overwhelming abundance, birders come from all over the world to try to catch glimpses of species that can be found nowhere else, such as toucans and antbirds, motmots and manakins, bellbirds and cocks-of-the-rock, and practically all of the planet's hummingbirds. Two such birding enthusiasts are Vera and Bob Thornton, who have spent fifteen years photographing these special and exotic birds in...