Life lists are something the vast majority of birders keep, no matter their experience level. A life list is simply a list of all the birds one has observed in the wild. When you observe a bird you have never seen before, you add it to your life list. The American Birding Association actually has well-defined rules and regulations of what you can and cannot to your life list (of course, you can choose to follow those how you please). If you are interested in the world of listing, here is the website for the ABA that includes a link to the rules.
With that in mind, a common goal for many birders is to add birds to their life list. I’ve always likened birding to be a real life Pokemon: gotta catch ’em all! In fact, many birders, including myself, are subscribed to email alerts and listservs that alert us of either rare birds or birds we still need for our life list. So, with the desire to continually add more and more birds to one’s life list, is there a way compare year-to-year life bird additions? That is, how can I compare the total number of new life birds I observed this year to, say, last year, or the year before, etc.?
This seems like such a trivial question, but I hope you’ll that it is actually quite a complex question to answer! A first temptation might just be to simply compare raw totals from year-to-year. So, if I saw 72 new birds in 2016 but only 65 new birds in 2017, I would say that 2016 was a better year than 2017 based on number of new birds seen. You might recall from a previous post where I analyze my birding data that I made a simple bar plot of my life list additions by year. Here was that plot:
Why might yearly life bird additions not necessarily be a good metric?
Recall that in my previous post, one of the other metrics I looked at was number of yearly checklists as an indicator of effort. In the case of yearly checklist totals, there isn’t really an upper limit to how many checklists I can submit throughout the year. Additionally, the number of checklists I submit in any previous year will not necessarily influence the number of checklists I will submit this year.
These statements are not necessarily true for life bird additions. For the sake of my argument, I will limit myself to birding only in the province of Ontario. The Ontario Field Ornithologists list 496 birds on their Ontario Checklist. So, if I were to only bird in Ontario, 496 would be my upper limit for total species. More importantly, however, is that it would also follow that as I add more birds to my Ontario life list, I continually have less and less birds to be able to choose from to keep adding to my Ontario life list; how many life birds I find in previous years will affect how many life birds I may be able to find this year.
This is the premise behind this series of blog posts that I am starting this year. I want to try to come up with some sort of qualifier to compare year-to-year life bird additions. I want to be able to explicitly state: “based on the number of life birds I saw this year, this was a _______ year of birding”, where the blank could be something as simple as “good” or “bad”. Obviously, the number of new life birds one sees in a year is not the only indicator of how good or bad their year was. However, this is just an indicator I would like to investigate.
So, for at least this year, I will be creating blog posts that explore possible solutions to this problem: a problem I will call the “Life List Problem“. (If you can think of a better name, do let me know). These solutions will likely be iterative improvements; that is, each solution will improve on the previous solutions. This series is going to be highly dependent on the amount of free time I have, of course, but I hope to have a new solution posted at least once per month. I already have most of solution 1 ready to go, so watch out for that in the coming days!
On a final note, know that I am just one person that is still taking some basic math and stats courses. So, as this series moves along, I would be happy to listen to some of your ideas and suggestions of things I could investigate, and in fact I encourage you to think about this problem with me! Any problem is made easier to solve when you add more brain power to it, so I am happy to accept any suggestions throughout the series!