Every June for the past 18 years, Matt Pelikan has dedicated a day to a very particular drive. He wakes up early—early enough to be on the road by 4:30 a.m.—straps on his binoculars, and drives to the same spot on the northwestern side of Martha’s Vineyard, a small vacationing island off the coast of Massachusetts. From there, he follows the same 25-mile route every year, winding his way across the island and pulling his car over every half mile to stand on the side of the road. He stays there for three minutes, tallying every bird species he sees or hears, and then drives to the next stop. The full trip, including all 50 stops, takes up most of his morning. Pelikan’s route is one of some 4,000 25-mile routes driven by volunteer birders every year as part of the North American Breeding Bird Survey, now in its 50th year. This year, on June 4, Pelikan—a Nature Conservancy ecologist and author of the Martha's Vineyard Times column “Wild Side”—tallied about 60 bird...