Mysticete
Well-known member
Sounds odd . . . so as of next year, they'll have Thayer's on their 2017 yearlist but not on their life list. That just doesn't make sense!
Actually Thayer's won't be on the 2017 list either. As I stated, the annual checklist update goes into effect with the November publication.
Traditionally the big year in North America is treated as a snap shot of the current state of bird knowledge. You can only count what is still on the list by the close of the year, and can't keep in reserve future splits/introductions, nor is it influenced by future lumps and extirpations. The only exception being ABA first records which may not get voted on until after the year comes to a close.
Why this exists is because:
Tradition: strict rules for ABA big years were never laid down in an organized manner, rather early participants (Sandy Komito and others) created the rule.
Archival: I would imagine many big year participants with significant years have already passed away or our otherwise out of birding. There is no official "record keeper" for these past attempts who can continually update those lists. It's also likely that even if there was, I am skeptical that notes and journals may always be sufficient to correctly identify split taxa. Thus, by allowing them to be snapshots in time, there are stable numbers that can be compared over the years. It would be a huge pain in the butt if ABA had to go and update each list every year, especially since people doing big years only have to provide a number, not a list of taxa and dates/locations.
Knowledge: Finally, I suspect the actual ease in identifying different forms to be split is something that has grown incredibly easy with the aid of the internet. I am not sure how readily available that data was, or even if it really existed. We know way way way more about bird identification and phylogeography nowadays than we did then. Birders might have never recorded sufficient knowledge or gone after an easier to ID population because they didn't realize they had to.