This topic seems to create controversy among birders; either you are, or are not a lister, and adamant about your choice. I am a lister, and let me tell you why. One of the joys of birding for me is making observations, and then recording your observation for future reference. The observation is what you saw, and when and where you saw it. It may be my science background, but this tabulation or listing just seems like a natural outcome of birding. When I first started birding I kept no list, then it evolved into random scraps of paper and notebooks, and finally into a computer program organizing the observations. Today it has reached the ultimate of ease and utility via the Cornell web-site http://www.ebird.org. If you don’t use this site I would strongly encourage you to investigate it.
When I return from a birding outing I take a few moments to enter ebird and list my observations. They make it easy. You enter the birding site on a map (or click on a previously entered site), tell them the time, date, and number of what you saw by using their birding list specifically tailored to your place and season of observation, and click enter. The program saves your observations and places them in your personal lists sorted by year, month, location (yard, neighborhood, county, state, country, etc.). It also places your data in a growing world-wide data base, accessible by you, and shows you what others are seeing in your area. When I travel to a new birding site, foreign or domestic, I first go to ebird and see what birds to expect at that site at that time of year. You can access migration data, rarities, and even get alerts when rarities show up in your state. In summary, in a small way you have added to the science of ornithology, and at the same time kept your personal list.
I’m not one to brag about my list–its pretty small, less than 1000. But listing for me adds this additional organizing enjoyment to an already rewarding pastime.