Taxonomy and the British List

20 January 2017

The British Ornithologists’ Union (BOU) recognises the value of, and is keen to move towards, a standardised global avian taxonomy. As such we wish to adopt one of the current global taxonomies, and use this for all BOU activities, including the British List.

From 1 January 2018 the BOU will adopt the International Ornithological Congress (IOC) World Bird List for all its taxonomic needs, including the British List. This follows a detailed review by the BOU’s Records Committee (BOURC).

Criteria for assessing selection of a taxonomic system

In August 2016 a joint meeting of BOURC and representatives of BOU Council met to draw up the criteria to select a new taxonomy, and agreed to ask the four main global avian taxonomic systems (eBird/Clements, HBW/BirdLife, Howard & Moore and IOC World Bird List) to submit a proposal that could be assessed against the agreed criteria and related questions (provided below).

As a scientific organisation, the BOU needs a global taxonomic system that meets the following criteria:

  • Uses a consistent scientific approach to taxonomic decisions including higher level systematics.
  • Uses a transparent system in which the scientific rationale for taxonomic decisions is clearly articulated, both in general terms and for individual decisions.
  • Is reviewed and updated frequently to keep pace with scientific developments, new studies and new information.
  • Is not biased in quality or geographic focus (including when updating the taxonomy) in a manner that results in insufficient attention being given to species that will influence the British list, or inconsistencies to arise between different geographic regions.
  • Includes extinct birds (due to creation of category F of the British List).

The focus of our decision is on taxonomic classifications. The selection of a global taxonomic system will thus not be influenced by a taxonomy’s approach towards the choice or spelling of English names as we recognise the binomial name forms the appropriate basis of scientific species lists.
We invite you to submit your classification for our consideration. In doing so, we ask you to answer specifically the 11 questions set out here.

  1. What is the frequency of reviewing and updating a) the species level taxonomy, and b) systematic decisions at higher taxonomic levels?
  2. In what format are updates released and how do these highlight changes relative to the previous version?
  3. Please summarise the scientific approach used to deciding a) taxonomic species limits and b) higher level systematic classifications.
  4. Summarise the processes that you will use to update species level taxonomy in your next update. In particular, please explain how you obtain new data that is relevant to taxonomic decisions, who is responsible for interpreting these data (including the number of people and their expertise), and the process of reporting decisions and their rationale.
  5. Does your taxonomy list subspecies? If so what approach is used to define sub-species, and how is new scientific information obtained and incorporated into updates relating to sub-species classification?
  6. If there is variation in the process of updating species level taxonomies for different geographical regions please explain these differences, and how consistency across regions is ensured.
  7. What is the process that you will use for updating the taxonomy above the species level in your next update (genera, families etc.)? Please explain how you obtain new data that is relevant to taxonomic decisions, who is responsible for interpreting these data (including the number of people and their expertise), and the process of reporting decisions and their rationale.
  8. What systems are in place to maintain consistency of taxonomic decisions within and between updates?
  9. What systems are in place to ensure long-term continuity of maintaining and updating your taxonomy in the mid to long-term future?
  10. Are there likely to be any changes in your approach in the next five to ten years that will influence responses to any of the above questions? If so, please outline what these changes are/might be.
  11. Is there a programme of periodic review of the approaches and processes disclosed in your replies to the above questions and, if so, how frequently is or are such review or reviews undertaken?

Process in selecting a new taxonomy

In September 2016 the four recognised taxonomic groups (eBird/Clements, HBW/BirdLife, Howard & Moore and IOC World Bird List) were invited to submit proposals against the above criteria by 31 October. All four groups submitted proposals and these were circulated to members of BOURC and BOU Council.

Initially, the BOU Council appointed a delegation which held a conference call to discuss the merits of each proposal and to arrive at a view on behalf of Council. This delegation reviewed the proposals but did not consider that there was any strong reason to make any recommendation for any of the candidate taxonomies ahead of a full meeting of BOURC.

BOURC subsequently met on 10 December 2016. BOURC invited the members of the Council delegation to attend, of whom two were able to be present. The Council delegates engaged in discussions but had no vote in the process. It was expected a recommendation to BOU Council would be made as a result of the meeting. All members of BOURC, bar one, were present.

Before discussing the taxonomic proposals in detail, the Committee considered two issues raised by those present. First, the need for and benefits of a unified global taxonomy was agreed upon. Second, it was agreed that the EU’s current use of the HBW/BirdLife taxonomy would not be a material factor influencing the Committee’s discussions.

The Howard & Moore proposal was discussed first as this was the only proposal for a taxonomic system which was not currently available online, and the Committee felt that accessibility of the new taxonomy to be adopted was important. With no online version envisaged until the next update (which was said to be some years away), the Committee concluded that this proposal would not be considered further.

In their respective submissions, the IOC World Bird List and eBird/Clements had stated their increasing collaboration, and their agreement that a single global taxonomy was desirable. On the latter point the International Ornithologists’ Union (IOU) has stated that they intend to have a session at IOC2018 in Vancouver, Canada in August 2018 looking at ways to progress to a unified global taxonomy.

This left the Committee with two alternatives: HBW/BirdLife on one side and IOC World Bird List and eBird /Clements on the other.

Arguments were advanced in support of both alternatives, and the BOURC members at the meeting were evenly split between adopting either HBW/BirdLife or the IOC World Bird List. From a show of hands during which the Chair abstained, there were four votes on each side. Each member of the Committee then summarised his or her reasoning, and members were given the opportunity to reconsider their vote.

The outcome remained unchanged, so the Chair used his casting vote to recommend that the BOU adopt the IOC World Bird List.

It was emphasised that this decision was influenced by the expectation of a move towards a more unified global taxonomy, and in that respect the BOU should work with IOU/IOC to ensure that this occurs.

In summarising his reasons for the recommendation the Chair expressed the view that moving to the IOC World Bird List would be the most likely way of achieving a more unified global taxonomy, especially in light of the proposed meeting at IOC2018. He also stated that this move would be more in keeping with the BOU’s previous approach to taxonomy, and in many quarters would have greater scientific credibility.

Members were given a final opportunity to contribute or object before the outcome was accepted.

This decision will be reviewed in 5 years time.

18 August 2016

Adoption of a global taxonomy

The Council of the British Ornithologists’ Union (BOU) recognises the value of the global harmonisation of avian taxonomy. Following unsuccessful attempts to seek an agreed European taxonomy it was announced in November 2015 that the BOU would disband its own Taxonomic Sub-committee and review the available global taxonomies with a view to adopt one system for all BOU activities, including the British List (for more information see

Notably, moving towards a single international harmonised taxonomy is one of the declared aims of the International Ornithologists’ Union (IOU), with a round table meeting being convened at 27th International Ornithological Congress in Vancouver, Canada in August 2018. However, BOU recognises that it may be many years before this is achieved and would like to harmonise its own taxonomy with a global list more rapidly, rather than waiting for a final global consensus to emerge.

A working group from BOU Council and the BOU Records Committee (BOURC) met in August 2016 to determine the criteria to be considered and the process for selecting which global taxonomy to adopt. Factors to be considered will include the regularity of updates to the taxonomy, and the extent to which the process for decision making is open and transparent, as well as being scientifically valid and consistent. The major current global taxonomies (Bird-Life International/HBW, Clements, IOC, Howard and Moore) will be contacted shortly and invited to provide information relating to these criteria. All of this information will be considered at a joint meeting of BOU Council and BOURC, following which a decision will be made regarding which global taxonomic system will be followed by BOU.

6 November 2015

For many years the BOU has been seeking to establish a unified European-wide taxonomic model. However, despite the best efforts of our own taxonomic group, little progress has been made, with five separate national taxonomic groups (including our own) not being able to reach a consensus via the Association of European Records and Rarities Committees (AERC) since its establishment in 1991.

With no resolution in sight, BOU Council feels that the continued existence of national groups, each understandably feeling an obligation to retain control of the taxonomy used for their own national lists, is not in the best interests of ornithology and is a barrier preventing the establishment of a unified European taxonomy.

With a view to resolving this issue, the BOU has therefore disbanded its own Taxonomic Sub-committee and we will now take time to review the available global taxonomies with a view to adopting one system for all BOU activities, including The British List. This decision does not imply any criticism of the excellent work carried out by the BOU’s Taxonomic Sub-committee over the years, but is a reflection of the importance that BOU Council places on establishing a unified European avian taxonomy.

Prior to the above, the BOU’s Taxonomic Sub-committee published their own guidelines on assigning species rank relating to the British List followed by a series of reports with taxonomic recommendations. These recommendations are considered by the Records Committee (BOURC) and are formally applied to the List on adoption by BOURC in their own reports.

BOURC Taxonomic Sub-committee – 11th report
Ibis 158: 206–212 (January 2016)

BOURC Taxonomic Sub-committee – 10th report
Ibis 157: 193–200 (January 2015)

BOURC Taxonomic Sub-committee – 9th report
Ibis 155: 898-907 (October 2013)

BOURC Taxonomic Sub-committee – 8th report
Ibis 154: 874-883 (October 2012)

BOURC Taxonomic Sub-committee – 7th report
Ibis 153: 883-892 (October 2011)

BOURC Taxonomic Sub-committee – 6th report
Ibis 152: 180-186 (January 2010)

BOURC Taxonomic Sub-committee – 5th report
Ibis 150: 833-835 (October 2008)

BOURC Taxonomic Sub-committee – 4th report
Ibis 149: 853-857 (October 2007)

BOURC Taxonomic Sub-committee – 3rd report
Ibis 147: 821-826 (October 2005)

BOURC Taxonomic Sub-committee – 2nd report
Ibis 146: 153-157 (January 2004)

BOURC Taxonomic Sub-committee – 1st report
Ibis 144: 707-710 (October 2002)

BOU Guidelines for assigning species rank
Ibis 144: 518-525 (July 2002)