I thought every birder did this. Do we not all do this? I chased some birds this winter, eventually finding my milestone 700th ABA Continental bird—a Common Gull in Eastport, Maine. Afterward, I shared some photos on Twitter of the handwritten notations I made in my Sibley field guide and got a lot of responses. Many birders said they do the same, and shared images of their well-loved books. Others had their own methods of keeping physical records. But some responses caught me off guard: What an interesting idea to keep a physical copy of your life list in a field guide! Or, wow, I never thought of that! Or even: I’d never mark up a book like that. These comments surprised me because writing down lifers in my field guides is something I’ve always done, and it's something that I’ve always assumed all birders did since the exact moment I started birding. To those who don’t do this or have never heard of the practice, please listen: Do it. It’s the best. I began...