One of the questions the RSEC receives most frequently is about which populations of introduced species may be counted in the ABA Area.

Version 2020 of the ABA Recording Rules and Interpretations has updated Rule 2.B(v) to help clarify the answer to this question. Previously, the rule said that a bird is countable if from a population that met the ABA Checklist Committee’s Criteria for Determining Establishment of Exotics. However, the RSEC recognizes that criterion #8—which states that a publication must document the first seven criteria—would rarely be met for established populations that were not the basis for the initial addition of an introduced species to the Checklist. Therefore, Rule 2.B(v) now says that only the first seven criteria are required for a population to be countable.

Perhaps the best indicator of a countable population is whether it meets criterion #6, which reads:

To help birders decide where and when they may count introduced species, we have compiled a list of populations of introduced species on the ABA Checklist that have been present for at least 15 years (as of 2020) and appear to meet the other criteria for being considered established. Your life list is your own, of course, but the current RSEC position is that birds from any of the populations listed below may be counted by birders wishing to do so if seen during or after the year provided. And to be clear, these dates of countability are applicable to Life Lists, not Big Year Lists. The Big Year Rules state “Each species counted by the participant must have been encountered in accordance with the ABA Recording Rules current at the time the species was encountered.” Thus, introduced birds counted during Big Years prior to 2020 must have belonged to populations that met all eight Criteria for Determining Establishment of Exotics.

Please note that some of the species on this list also may occur as countable vagrants from native populations (e.g., Eurasian Skylark).

Please note that this list of countable populations may not be exhaustive and is subject to deletions and additions based on any updated understanding. The RSEC welcomes feedback on this list as well: rsec@aba.org.

The ABA and RSEC would like to thank Nick Block, RSEC Secretary from 2015–2020, for creating and maintaining this list.