Bird splits and lumps: why your list count changes

In birding, a split is when scientists divide one species into two or more, and a lump is when they merge two or more species into one. Either can change your life list without a new sighting: a split can add a species you'd already seen, and a lump can take one away.

That's why your total can move while you sit at home. Here's what each one means, the recent changes North American birders noticed, and what happens to your records.

Check your own list: our free splits and lumps checker shows which of your birds were touched, and every split, lump and name change since 2018 has its own page.

Key facts

• Herring Gull became four species in August 2025 (AOS). For most US birders, theirs is now American Herring Gull.
• Redpolls: in July 2024 the AOS merged Hoary and Lesser Redpoll with Common Redpoll, now one species.
• eBird updates its taxonomy once a year, in October, and applies the changes to your old records for you.
• eBird's 2026 update began on October 27, 2026, and eBird now calls it complete: 39 species gained through splits, 7 lost through lumps and 2 newly described, for 11,201 species worldwide, eBird says. For the US and Canada it split the Willet, the Marsh Wren and the Tufted Flycatcher, and kept one Great Egret, which the AOS had split.
• AviList, the shared global checklist first published in June 2025, published its 2026 edition on October 20, 2026. It splits Willet and Marsh Wren, and now Warbling Vireo too: what changed in AviList 2026.

Facts checked: September 30, 2026; AviList's 2026 edition added October 21, 2026; eBird's 2026 update added October 29 and completed November 10, 2026.

Recent changes at a glance

The details of each are below; our splits and lumps list has a page for each, with more changes from 2018 to 2025, such as Gray Jay becoming Canada Jay.

Not every checklist change is a split or a lump. In 2026 the AOS also added three birds to the US list on new records, among them a harrier known from a single wing: the new US birds of 2026.

What is a split?

A split is when scientists decide that what was treated as one species is really two or more. Each new species gets its own name, and each can go on your list on its own.

Splits come from new evidence. When the American Ornithological Society (AOS) split Herring Gull in 2025, it pointed to differences in genes, appearance, ecology and voice.

If you've already seen both of the new species, a split can add a bird to your list without a new sighting.

What is a lump?

A lump is the reverse: two or more species are merged into one, because the evidence says they belong together. If you had counted both, your list goes down by one.

Recent examples

Herring Gull became four species (2025)

In August 2025 the AOS split Herring Gull four ways: American Herring Gull, Vega Gull, European Herring Gull and Mongolian Gull. According to Kenn Kaufman in Audubon magazine, American Herring Gull is the one to expect almost everywhere in North America. Vega Gull is the common one in parts of western Alaska. European Herring Gull is a very rare visitor to eastern Canada, and Mongolian Gull lives in Asia.

So for most US birders, the gull in their notebook is now called American Herring Gull, and the count doesn't change. Someone who has also seen a Vega Gull in Alaska gains a species.

Yellow Warbler and Whimbrel (2025)

In October 2025, eBird's checklist (Clements) split two familiar birds:

• Yellow Warbler became Northern Yellow Warbler and Mangrove Yellow Warbler.
• Whimbrel became Hudsonian Whimbrel and Eurasian Whimbrel.

The ABA added all four to its checklist in January 2026. Northern Yellow Warbler and Hudsonian Whimbrel are the common ones here. Mangrove Yellow Warbler breeds in the Florida Keys and locally in Texas, and Eurasian Whimbrel is a rare visitor.

Names can differ even when checklists agree on the species. AviList, the new global checklist, calls the same two warblers American Yellow Warbler and Mangrove Warbler.

The redpolls became one (2024)

In July 2024 the AOS lumped Hoary Redpoll and Lesser Redpoll with Common Redpoll. There is now one species, called simply Redpoll. Kaufman noted that birders no longer have to decide whether a pale bird is pale enough to count. If you had both Common and Hoary on your list, your total dropped by one.

When checklists disagree: Warbling Vireo

The AOS (August 2025) and eBird/Clements (October 2025) both split Warbling Vireo into an eastern and a western species. AviList followed only in its 2026 edition, on October 20, 2026; its June 2026 edition, v2025b, still treats it as one. Same birds, same sightings, but for a year a different total depending on the checklist.

Most splits give your bird a new name, not a new species

Most of the splits on our list of changes change a name for US birders, not their count. The bird you saw still lives here under a new name, and the other new species live far away. Your total goes up only if you have seen one of those too. Some examples:

Sometimes the US bird even keeps its name. When White-winged Scoter became three species, in 2018 and 2019, the North American bird stayed White-winged Scoter. The new ones are the Velvet Scoter of Europe and Stejneger's Scoter of Asia, which strays to Alaska.

A split can add a species without a trip abroad, though. Since 2022 the meadowlarks of the desert grasslands of Arizona, New Mexico and west Texas have been a species of their own, the Chihuahuan Meadowlark, so if you have seen meadowlarks there and in the East, you gain one: see the Eastern Meadowlark split. Birders call a species gained this way an "armchair lifer."

Some changes aren't splits at all, only new English names, and they never change your count. In 2019 the AOS renamed the Blue-throated Hummingbird Blue-throated Mountain-gem, to give its group one shared name. In 2020 it renamed McCown's Longspur Thick-billed Longspur, because the man it honored had become a Confederate general.

Older names still turn up in field guides and on lists kept for decades. The Oldsquaw has been the Long-tailed Duck since 2000, a new name only; the Rufous-sided Towhee has been two species, the Eastern and Spotted Towhees, since 1995.

Why your total changes by itself

As eBird's help puts it, "new splits or lumps are regularly justified." Checklists are updated on a schedule:

• eBird updates its taxonomy once a year, in October.
• The AOS publishes yearly supplements to its North American checklist. The last two came out in July 2024 and August 2025.
• AviList publishes one edition a year, in October. Its 2026 edition came out on October 20, 2026.

So as we write this, at the end of September 2026, the next round of changes is only weeks away. If you keep a paper copy of your list, the weeks after eBird's October update are a good time to print your life list again, with the new names.

When an update arrives, apps such as eBird apply it to your old records for you. eBird's help page explains one catch. If you logged a bird under a recognizable subspecies group, the record moves neatly to the matching new species. If you logged it only under the old species name, it may become an "either/or" record, which doesn't count as a species.

A tip for the future: when your app lets you record a recognizable form, and you're sure which one you saw, record it. eBird's own example is Yellow-rumped Warbler, which you can log as "Myrtle" or "Audubon's".

Which checklist is right?

None of them is wrong. A checklist is the best scientific judgment at the time, and it changes as evidence comes in.

AviList was launched in June 2025 to bring the world's main checklists together. Its partners include the AOS, the Cornell Lab of Ornithology, BirdLife International, the International Ornithologists' Union and Avibase. The IOC World Bird List has stopped at version 15.2, and eBird/Clements is making final changes through 2026 to line up with AviList. With its 2026 edition, AviList says 97.7 percent of its species match eBird's. So we expect the totals in different apps to drift closer together over time.

For what these changes mean for the total number of species in the US and Canada, see how many bird species are in the US and Canada.

How our books handle it

Birdfolio matches every record in your file to a species on AviList (its October 2026 edition, v2026, since October 22, 2026), and we credit AviList in every book. Here's what that means for you:

• Familiar names. Where AviList lists the eBird name for a species, we print that one: since its October 2026 edition, the name AviList gives for eBird's 2026 update. You'll see "Northern Yellow Warbler", as in your eBird list.
• Older names are placed for you. eBird and iNaturalist files include scientific names, which let us place older records. A Hoary Redpoll (Acanthis hornemanni) in your file goes under Redpoll. A notes page in the book lists every change like this. Before you order, the preview shows the same list under "Name changes we handled".
• Uncertain records are kept, not counted. A "gull sp." or a "Greater/Lesser Yellowlegs" appears on an "also recorded" page, not in your species total.
• No guessing. If we can't match a name, which can happen with an old name in a typed list, the preview tells you. You can then check the spelling or use today's name.

Because checklists don't change on the same day, your book's total can occasionally differ from your app's. In late October 2026, for example, AviList and our books already counted two Tufted Flycatchers while eBird's 2026 update, still rolling out, hadn't shown that split; eBird and our books now agree on two of each for the Willet, the Marsh Wren and the Tufted Flycatcher.

To see how a finished book looks, page through a Birdfolio. For the basics, start with what is a life list?

Birdfolio is not affiliated with eBird, the Cornell Lab of Ornithology or iNaturalist.