When Liron Gertsman’s flight to St. Paul Island, part of a volcanic archipelago in the Bering Sea, was canceled due to an incoming storm, he wasn’t too upset. The 17-year-old was heading to the birding hotspot with his father to celebrate his high school graduation, but the two had decided to spend a few days in Anchorage before the flight. Now they had an extra unplanned day—and a loon they wanted to see again. When the two first arrived in Anchorage, a local birder had told them about a lake not far from downtown known to have a friendly summering Red-throated Loon, a rarity that far south in its full breeding plumage, Gertsman says. The morning after he got the tip, he and his father drove to the lake without success. But returning to the site that evening, he spotted the loon fishing out on the water as soon as they stepped out of the car. Once at the lake’s edge, Gertsman found the bird more than lived up to its sociable reputation. “It surfaced right in...