Archived 2016 topics: Black-tailed Monarch (Monarcha verticalis) is being split: list S. ateralbus as Vulnerable?

This is part of a consultation on the Red List implications of extensive changes to BirdLife’s taxonomy for passerines

Lynx Edicions and BirdLife International will soon publish the second volume of the HBW-BirdLife Illustrated Checklist of the Birds of the World, building off the Handbook of the Birds of the World series, and BirdLife’s annually updated taxonomic checklist.

The new Checklist will be based on the application of criteria for recognising species limits described by Tobias et al. (2010). Full details of the specific scores and the basis of these for each new taxonomic revision will be provided in the Checklist.

Following publication, an open and transparent mechanism will be established to allow people to comment on the taxonomic revisions or suggest new ones, and provide new information of relevance in order to inform regular updates. We are also actively seeking input via a discussion topic here regarding some potential taxonomic revisions that currently lack sufficient information.

The new Checklist will form the taxonomic basis of BirdLife’s assessments of the status of the world’s birds for the IUCN Red List. The taxonomic changes that will appear in volume 2 of the checklist (for passerines) will begin to be incorporated into the 2016 Red List update, with the remainder to be incorporated into subsequent Red List updates.

Preliminary Red List assessments have been carried out for the newly split or lumped taxa. We are now requesting comments and feedback on these preliminary assessments.

Black-tailed Monarch Monarcha verticalis is being moved into the genus Symposiachrus and split into Symposiachrus verticalis and Symposiachrus ateralbus, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, Monarcha verticalis (BirdLife species factsheet) was listed as Least Concern, on the basis that it was not considered to approach the thresholds for listing as Vulnerable under any criteria. The pre-split species was characterised as being common or locally common to scarce, and occurred in lowland and hill primary forest and bamboo thickets (Clement 2016).

Symposiachrus verticalis (as defined following the taxonomic change) is found on throughout much of the Bismark Archipelago, including New Hanover, New Ireland and New Britain. It is not considered to approach the thresholds for listing as Vulnerable under any criteria, despite a relatively restricted distribution. S. verticalis is suggested to be listed as Least Concern.

S. ateralbus is restricted to the island of Djaul, off the southern coast of northwest New Ireland. The species was recorded during visits to the island in 1964, 1996 and 2007 (Dutson 2007), and several times since. Together with S. verticalis it was considered fairly common in closed canopy forest but less common in secondary forest by Dutson (2011).

The Extent of Occurrence of the newly split species is 186km2. The population is estimated to number between 2,500-9,999 individualsbased on an assessment of known records, descriptions of abundance and range size. This is consistent with recorded population density estimates for congeners or close relatives with a similar body size, and the fact that only a proportion of the estimated Extent of Occurrence is likely to be occupied. This estimate is equivalent to 1,667-6,666 mature individuals, rounded here to 1,500-7,000 mature individuals.

There remains a reasonable percentage of forest on Djaul, however there appears to have been significant loss in forest over the past three-generation period for the species (c13 years) (Hansen et al. 2013), from which a minor, slow but ongoing population decline is inferred.

It is suggested that Djaul Monarch S. ateralbus is listed as Vulnerable under criterion C2a(ii), on the basis that it has a small, single population that is suffering an ongoing slow decline.

Comments are invited on these proposed categories and further information would be welcomed.


Clement, P. (2016). Black-tailed Monarch (Monarcha verticalis). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from on 12 October 2016).

Dutson, G. 2007. The birds of Djaul Island, New Ireland. Muruk 8: 133-139.

Dutson, G. 2011. Birds of Melanesia: Bismarcks, Solomons, Vanuatu and New Caledonia. Christopher Helm, London.

Eastwood, C. 1996. Kavieng, Djaul and Mussau island, New Ireland: a trip report. Muruk 8: 28-32.

Hansen, M. C., P. V. Potapov, R. Moore, M. Hancher, S. A. Turubanova, A. Tyukavina, D. Thau, S. V. Stehman, S. J. Goetz, T. R. Loveland, A. Kommareddy, A. Egorov, L. Chini, C. O. Justice, and J. R. G. Townshend. 2013. High-Resolution Global Maps of 21st-Century Forest Cover Change. Science 342: 850–53. Data available from:

Tobias, J. A., Seddon, N., Spottiswoode, C. N., Pilgrim, J. D., Fishpool, L. D. C. and Collar, N. J. 2010. Quantitative criteria for species delimitation. Ibis 152: 724–746.

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2 Responses to Archived 2016 topics: Black-tailed Monarch (Monarcha verticalis) is being split: list S. ateralbus as Vulnerable?

  1. Guy Dutson says:

    In 1997, I saw or heard 16 S. ateralbus in 25 hours in mixed secondary forest on Djaul, nearby all in or close to patches of shady old-growth with large trees, consistent with the assessment above.

  2. James Westrip (BirdLife) says:

    Based on available information, our preliminary proposal for the 2016 Red List would be to adopt the proposed classifications outlined in the initial forum discussion.

    There is now a period for further comments until the final deadline of 28 October, after which the recommended categorisations will be put forward to IUCN.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from those in the initial proposal.

    The final 2016 Red List categories will be published on the BirdLife and IUCN websites in early December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

Comments are closed.