I find the various deviations here at IOC and in Clements (see separate chain) from SACC and NACC to be very interesting. Probably it is all coming from the new WGAC group:
Working Group Avian Checklists News (June 2022) As of 10 June 2022, the WGAC Taxonomic group has: Assembled a team, developed a process, implemented a technical tool (GitHub) to post issues, vote on them, summarize decisions, and preserve the process and data so they can be permanently archived...
www.internationalornithology.org
NACC has always been somewhat conservative, albeit generally pretty consistent over the years; SACC has had a lot of problems in terms of keeping up, and also with being non-progressive, inconsistent and biased towards different groups of researchers. I've written a lot more about the issues with that committee here:
IOC has always gone its own way apart from NACC and SACC, e.g. accepting the "Ridgely splits" of the 1980s to 1990s and also on more recent literature and some BirdLife splits. However, Clements has often even been behind SACC and NACC, waiting for them to act, then taking even longer to follow.
We then had the disruptor of the BirdLife / Collar checklist, most of which I think is right, some of which is clearly not. And then some proponents of "old taxonomies" laying into the BirdLife list on the ones they got wrong. WGAC is now looking at all those proposals it seems and, seemingly, taking many of them.
It is quite clear that whilst WGAC is being overall pretty progressive and drawing a fairly progressive middle line between the various competing lists, some of the naysayers, flat-earthers or proponents of slow change (which the rate of publication of studies they deem to be satisfactory will only ever produce) have been trying to push back.
We had these NACC proposals recently remember, being various one-sided hatchet jobs aimed at trashing some reasonable BirdLife changes that do not benefit from a full molecular, vocal and specimen study in the journal Auk; NACC turned most of these down in the end. These were separately discussed here on Birdforum with a strong rebuttal from Peter Boesman, especially on Spot-crowned Woodcreeper.
We then recently had a series of proposals at SACC, which seems quite openly to be an attempt to try and get ahead of WGAC and influence that process, e.g. one of them even said "this proposal is to provide feedback to IOC’s WGAC, which is working to reconcile all world lists". For "feedback", read "telling them why not to accept any changes from our inviolable and ever-unchanging SACC list". Several of these proposals recommended to reject splits adopted by other lists (although in the case of Piranga, I have to say that not splitting seems not unreasonable, and in the case of the Flame-rumped Tanagers I believe SACC is more correct in lumping; the others, which should be easier, are having a hard time getting over the usual blocking minority at SACC, perpetuated by the usual individual suspects at SACC). E.g.:
And then we now see Clements and IOC adopting a bunch of S American splits which SACC have not addressed or got round to having pre-emptive proposals on. That does seem to be a bit of a departure. Did SACC not know the WGAC were looking at those ones? Maybe they did, since there is a common committee member on both. Were there too many proposals and was there not enough bandwidth for SACC to get its pre-emptive proposals published on time? Maybe.
Fascinating stuff to observe, anyway. And I have to say, the outcomes at WGAC on groups that I know well or have seen it the field or studied, or read the studies on, all seem instinctively reasonable and sensible. Good job.
