One night four years ago, two boys were driving outside of Roswell, New Mexico, after a day of birding, when suddenly the unimaginable happened: a terrible car wreck. Ryan Beaulieu, 17, a bird enthusiast who had helped bring national attention to Sandia Crest, the highest point in New Mexico’s Sandia Mountains, and to the rosy-finches that congregate there in winter, was killed instantly. The other boy, Raymond VanBuskirk, was rushed to the hospital, where he received a full blood transfusion. Doctors immobilized his cracked elbow in a cast, wrapped his swollen head in bandages, and listed his condition as critical. When he finally came to, his family and friends cried in relief. But for Raymond, just 15 at the time, waking up meant facing an awful reality: Ryan, his best friend, was dead. “We basically lived together, we were together all the time,” says Raymond. “I probably saw him more than I saw my own family.” The tragic accident ended what...