Every species on the American Birding Association's checklist carries a number from 1 to 6, the ABA code. The code says how regularly the species occurs in the ABA Area, from birds that turn up every year in good numbers (Code 1) to birds that can no longer be found at all (Code 6). The checklist currently lists 1,161 species (version 8.19, January 2026). Bird-a-Day players run into the codes because Audubon's guide to the challenge points them to the species coded 1, 2 or 3.
The six codes at a glance
The definitions below are summarized from the ABA Checklist page. The examples are species whose codes the ABA Checklist Committee set or changed in its 2023 report and its January 2026 update.
| Code | ABA label | What the ABA definition says | Recent examples |
|---|---|---|---|
| 1 | Regular | Regularly occurring breeders and visitors; more widespread and usually more numerous than Code 2 | Hudsonian Whimbrel, Northern Yellow Warbler (2026) |
| 2 | Regular | Regularly occurring, but with a restricted range in the ABA Area, lower densities, or habits so secretive that they are hard to detect | Mangrove Yellow Warbler (2026) |
| 3 | Rare | Occurs "in very low numbers, but annually"; includes visitors and rare breeding residents | Desertas Petrel (2026); Wood Sandpiper, moved up from Code 2 (2023) |
| 4 | Casual | Not recorded every year, but six or more records in total, including three or more in the past 30 years | Eurasian Whimbrel, Siberian Stonechat (2026); Siberian House-Martin (2023) |
| 5 | Accidental | Recorded five or fewer times in the ABA Area, or fewer than three records in the past 30 years | Waved Albatross (2026); Western Marsh Harrier, Icterine Warbler (2023) |
| 6 | Cannot be found | Probably or actually extinct or extirpated from the ABA Area, or surviving only in captivity or as released populations that have not yet re-established naturally | — |
The ABA Area, in the checklist page's words, "is essentially North America north of Mexico plus the Hawaiian Islands": the US states including Hawaii, Canada, the French islands of St. Pierre et Miquelon and adjacent waters. Bermuda, The Bahamas and Greenland are outside it.
- Code 1: regularly occurring breeders and visitors, more widespread and usually more numerous than Code 2.
- Code 2: regularly occurring, but with a restricted range, lower densities or secretive habits.
- Code 3 (Rare): very low numbers, but recorded every year.
- Code 4 (Casual): not annual; six or more records in total, three or more in the past 30 years.
- Code 5 (Accidental): five or fewer records, or fewer than three in the past 30 years.
- Code 6 (Cannot be found): probably or actually extinct or extirpated, or only captive or released populations.
- Bird-a-Day pool: Audubon (2017) points players to species coded 1, 2 or 3, more than 700 species in the US and Canada.
- Not every year: Codes 4 and 5 are not recorded annually; the ABA's weekly Rare Bird Alert has highlighted birds "of Code 4 or higher".
How to read the codes
- The line between 1 and 2 is soft. The ABA says "there is no firm designation between Code-1 and Code-2 species", and it "readily acknowledge[s] that some Code-2 species are harder to find than some species that have higher codes." A Code 2 bird can be secretive rather than scarce.
- Codes 4 and 5 are defined by counting records. The cut-offs are numerical: six or more records with three or more in the past 30 years makes a bird casual (Code 4); five or fewer, or fewer than three in 30 years, makes it accidental (Code 5).
- Codes measure occurrence, not conservation status. As a 2020 Nature NL article on Newfoundland's rarities puts it, "ABA rarity level only reflects the occurrence but not the conservation status of a species."
- Codes are continent-wide. Each definition refers to the ABA Area as a whole, so a code does not tell you how common a bird is in your county. For that, use local data such as eBird bar charts.
How codes are set and changed
The ABA Checklist Committee, "made up of experts on avian status and distribution," maintains, revises and publishes the checklist. Its page states that "Changes in ABA Codes shall be made by majority vote" of the committee, and its reports announce new species and code changes. Peter Pyle chairs the committee and signed the January 2026 report.
Codes move in three ways:
- A new species gets a code when it is added. The January 2026 report added Waved Albatross as Code 5, after a bird recorded over Cordell Bank, Marin County, California, on October 5, 2025.
- A split creates new codes. The same report replaced Whimbrel with Hudsonian Whimbrel (Code 1) and Eurasian Whimbrel (Code 4), and Yellow Warbler with Northern Yellow Warbler (Code 1) and Mangrove Yellow Warbler (Code 2).
- The committee re-codes a species. The 2023 report (Pyle et al.) moved Wood Sandpiper from Code 2 to Code 3 "to reflect its status as a vagrant relative to other Eurasian shorebirds."
The list size moves too: the September 2025 report brought it to 1,158 species and the January 2026 update to 1,161.
Three things that are not ABA codes
| Term | What it is | Example |
|---|---|---|
| Alpha code | A four-letter abbreviation of a species name; on the ABA Checklist these follow the American Ornithological Society's English names | WHIM (Hudsonian Whimbrel), MANW (Mangrove Yellow Warbler) |
| ABA Recording Rules | The rules on what makes a bird countable on ABA lists (version 2020) | Must be alive, wild and unrestrained |
| ABA Code of Birding Ethics | The ABA's ethics code; Recording Rule 5 requires that a bird be seen under conditions that follow it | "Never enter private property without the landowner's permission" |
Why the codes matter for challenges
Bird-a-Day. The game has no official rulebook; Audubon says "there's no such thing as the 'bird-a-day' police." Its 2017 article sends players to the species coded 1, 2 or 3, which it counts at more than 700 in the US and Canada. A full year needs 365 of them, one per day. Codes 1 and 2 are the regulars a year is built on. Code 3 birds occur every year but in very low numbers, so they are hard to plan around. Code 4 and 5 birds are not recorded every year at all: count them as windfall days, not as part of the plan. The species planner does the day-count arithmetic.
What counts. The code does not decide whether a bird counts. If you adopt the ABA Recording Rules as house rules, a bird must be within the area and time period when encountered, belong to a species on the ABA Checklist, be "alive, wild, and unrestrained," be identified by diagnostic features seen, heard or documented, and be encountered in line with the Code of Birding Ethics. The interpretations add that hybrids are not countable, a bird on a webcam does not count, and an introduced species counts only from an established population.
Big Years. The ABA Area Big Year rules run from 12:00 AM on January 1 to 11:59 PM on December 31, local time, and require each species to be on the ABA Checklist during that year. They do not mention codes, so a Code 5 vagrant counts the same as a Code 1 robin; the codes simply show which species are likely to be available. Big Year explained covers the rest of the rules and the record totals.
Chasing a rarity. The ABA's weekly Rare Bird Alert has used the codes as a filter, for example noting in December 2022 a rare bird "of Code 4 or higher" and listing a Social Flycatcher in Texas as Code 5. The Code of Birding Ethics asks birders to limit recordings and other audio lures, particularly in heavily birded areas and "for species that are rare in the area", and to share bird observations freely as long as that does not break the rest of the code.
Use the codes to build a target list
- Get the current checklist. The ABA Checklist page offers a PDF and a CSV download of version 8.19 (January 2026).
- Start with Codes 1 to 3. That is the pool Audubon recommends for a Bird-a-Day year.
- Localize it. Cross off species that do not occur in your area, using eBird bar charts for your county or state.
- Treat Code 3 birds as chances. Log them the day they appear; the challenge guide explains why the unusual bird of the day comes first.
- Write down your counting rules. Decide before Day 1 whether you follow the ABA Recording Rules, including heard-only birds, and keep the run in the streak tracker.
- Recheck after committee reports. Splits and new codes can change your list.
Quick checklist
- I know the difference between a code (how regular) and an alpha code (a four-letter name).
- My planning pool is Codes 1–3, trimmed to my own area.
- I don't count on Codes 4–5 birds; they are not recorded every year.
- My house rules say what counts (heard-only, wild birds only, no hybrids).
- I follow the Code of Birding Ethics when chasing a rare bird.
At year's end, the Bird-a-Day year in review compares 365 days with state and ABA species pools.
Sources
- ABA Checklist (version 8.19, January 2026; code definitions, ABA Area, downloads) — American Birding Association
- Listing & Taxonomy — American Birding Association
- ABA Checklist Committee (role, members, code changes by majority vote) — American Birding Association
- ABA Checklist Committee Report, January 2026 — Peter Pyle, American Birding Association
- 34th Report of the ABA Checklist Committee — Pyle et al., North American Birds 74(2), 2023 (PDF)
- ABA Recording Rules and Interpretations (version 2020) — American Birding Association
- ABA Area Big Year Rules — American Birding Association
- ABA Code of Birding Ethics — American Birding Association
- Rare Bird Alert: December 9, 2022 — Nate Swick, American Birding Association
- Boost Your Birding Skills by Seeing a New Bird Every Day This Year — Sharon Stiteler and Purbita Saha, Audubon (2017)
- Attu East: what makes us unique in the ABA? — Lancy Cheng and Megan Boucher, Nature NL (2020)