The cardinal was my gateway bird. Eight weeks ago, and newly quarantined at my in-laws, I joined my husband and five-year-old son at a nature preserve. They’d come for birds, equipped with binoculars and cameras; I’d just wanted out of the house. Not long into the walk, the wind picked up and misty rain started to fall. Damp and freezing, I was about to suggest turning back, when high in the tangle of barren tree branches, set against the soup-gray sky, was a tiny crimson silhouette. Suddenly I forgot about being cold and miserable. My mother is a dedicated birder, the kind who takes a bus to far-flung marshland to ogle an ibis. The allure mystified me. You saw a bird, then what? For my whole life, I zoned out whenever she talked about birds. But after tagging along on a few walks with my mother in Central Park, my son Arthur was asking for his own pair of binoculars and wanting my phone to scroll through Manhattan Bird Alert on Twitter. Arthur quickly became fluent in...