The number one thing you should know about Black Swifts is that pursuing them always leads to an adventure. You’re not guaranteed that when seeing most species—no birder ever regaled you with the thrilling story of the time they saw a House Sparrow—but as one of the most mysterious and difficult-to-find birds in North America, finding Black Swifts is never a snooze. My first attempt to chase them involved hiking deep into and up a canyon in western Colorado. I was dripping sweat and breathing heavy when our party reached our destination: Hanging Lake, a crystal-blue, waterfall-fed oasis tucked into the canyon. The fact that there were no Black Swifts around was almost forgotten amidst the scenery. (My lifer Williamson’s Sapsucker and Band-tailed Pigeon took some of the sting out, too.) Seeing the Black Swift’s close North American relatives, Chimney and Vaux’s Swifts, is decidedly unadventurous. They come to us, fluttering over cities and towns through summer and...