Many people who enjoy birds keep lists. Most keep a life list. Others keep all kinds of lists (patch list, county list, etc.) Why list?
First, some birders do not keep lists. They feel that focusing on listing interferes with enjoying the birds because you are recording your sighting instead of truly looking at and absorbing the experience. And that can happen, although I don't think listing and observation are mutually exclusive.
For those who list, there are various reasons.
- Competition. Having large life lists can be a big deal and people can become competitive. And yes, there are birding competitions, both formal and informal. If you haven't seen it, watch The Big Year. It's a comedy, and most birding people do find it funny. My husband, who has little interest in birds, didn't find it funny at all. He just didn't get some of the jokes. People do engage in big years. I followed the blog of a person doing an ABA-area big year (The ABA area is the 49 continental United States, the Hawaiian Islands, Canada, the French islands of St. Pierre et Miquelon, and adjacent waters to a distance of 200 miles from land or half the distance to a neighboring country, whichever is less.. Excluded by these boundaries are Bermuda, The Bahamas, and Greenland.) It wasn't a formal competition, but he was trying to see the most birds he could in a year in the area he selected and compare it to others who did the same thing in previous years. I also had an acquaintance who did a Texas big year. Big years are expensive projects. There are also Big Days (we used to do one of these as a fundraiser for Wild Bird Rescue), which is the number of birds you can find between midnight and 11:59 PM on a given day. I participate with the Wichita Wingmen in the Great Texas Birding Classic each year, which raises money for Texas Parks and Wildlife Conservation Grants. And yes, the focus is on the quantity, not the quality, of observations.
- Contributing to our knowledge of birds. We submit lists for the Christmas Bird Count and the Great Backyard Bird Count, for example. I also submit checklists to eBird when I go birding on my own (if you see a list of birds in a blog post, that list, which the specific numbers of each bird seen, is being submitted to eBird). Over time, lists submitted by many people in many locations, adds to our knowledge of bird populations and ranges.
- Memories. I like to look back at my lists to remember places I have been. For example, the illustration at the t op of this post comes from eBird. When I visited my son in Lisbon, Portugal earlier this year, we visited Parque Edwardo VII. Although I didn't go with the express purpose of watching birds, I did see some and recorded them. Now, when I look at the list, I can revisit the area in my mind.