Will Gladstone has a pretty hefty life list for a 13 year old. He’s spotted 190 species since he began keeping track about two years ago, after he heard three Pileated Woodpeckers squawking above him in the trees during a family vacation to Florida. Now, every weekend he asks his dad to take him to a new spot near their home in Massachusetts to study local birds. But he still hasn’t seen the one that’s taken up the most time and energy in his life: the Blue-footed Booby. Last April Will and his younger brother Matthew started the Blue Feet Foundation, which sells bright-blue socks embroidered with a likeness of the booby to raise money and awareness for the species. Overall, the wide-eyed birds, which inhabit a coastal stretch from northern Mexico to southern Peru, are doing just fine. But a small, fairly isolated population on the Galapagos Islands has slumped in recent decades. All told, between the 1960s and 2012, the Galapagos population shrank by about two-thirds...