AviList and Scythebill

This time, the blog takes a break from the usual release announcements to talk about the brand new AviList taxonomy, and how (and when) Scythebill will support it.

What's AviList?

AviList is a unified, global checklist of birds. After nearly seven years of work, it's just been made public. They plan to perform annual updates going forward.

A new checklist itself wouldn't be big news, but eBird, IOC, and BirdLife International; all participated in its development (as did many other notables), and have committed to converging on this single checklist.

When do the other checklists converge?

IOC will go first.  Its last release (15.2) is expected later this year, at which point their prodigious work comes to an end.

eBird comes next, replacing their taxonomy with the AviList taxonomy in October 2026 (though they only promise "near 100% alignment with AviList by its 2026 update" - emphasis added). I assume, but have not seen explicitly stated, that they will actually produce a custom taxonomy on top of AviList, adding groups and undescribed taxa on top of the core.

BirdLife - whose IUCN RedList assessments are included in Scythebill, but not its taxonomy - will take longer, as they need to perform new assessments on many taxa.

So... what about Scythebill?

It's clear that come the eBird update in 2026, Scythebill will be standardized on the AviList taxonomy (or, perhaps, the eBird extension, with groups and undescribed taxa), and will no longer need to support multiple bird taxonomies. (Though eBird's "near 100%" comment gives me pause.) This is great!

But what about now?  There are two issues with adding AviList v2025 as an additional taxonomic option right now:

• First, there are some shortcuts in the Scythebill code which assume two taxonomies (one primary - eBird, and one secondary - IOC).  Adding a third taxonomy means hunting down all potential bugs in this code, just to delete all that code in a year when we're down to one taxonomy.
• Second, AviList doesn't yet have an up-to-date subspecies list: "AviList v2025 started with a baseline list of subspecies from IOC v11.2 (July 2021), and this initial subspecies taxonomy has been largely carried through to AviList v2025". Because Scythebill uses subspecies (and indeed, relies on them for mapping between taxonomies), this is troublesome.
  

The first makes me hesitant to add AviList as a third option, though I'm not yet entirely ruling it out. The second makes it undesirable to replace IOC with AviList.  Because of this, my current plan is not to support AviList v2025.  And since the October 2026 update of eBird will (hopefully) make it silly to have both AviList and eBird, the simplest option is converging at that date.  As always, Scythebill will automatically update your records to that taxonomy when you upgrade.

I recognize this is a long delay, and birders are understandably eager to adopt this unified list.  That said, I believe the IOC 15.2 release will be very close to AviList v2025 at the species level (indeed, even eBird is already 99% aligned!), and I'm hoping that will be good enough for the majority of Scythebill users. If it's very different, I'll reconsider.

I do plan, though, to add the following features in the coming months:

• The Splits and Lumps report will let users see what AviList will change for their list, relative to both eBird and IOC
• All English name changes in AviList will be added as alternate names (ensuring that imports from AviList will be smooth).