Archived 2016 topics: Northern Fantail (Rhipidura rufiventris) is being split: list R. kordensis as Near Threatened?

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.

Northern Fantail Rhipidura rufiventris is being split into Timor Fantail R. rufiventris, Roti Fantail R. tenkatei, Banda Fantail R. hoedti, Buru Fantail R. bouruensis, Obi Fantail R. obiensis, Seram Fantail R. cinerea, Kai Fantail R. assimilis, Biak Fantail R. kordensis and Northern Fantail R. isura, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, Rhipidura rufiventris (BirdLife species factsheet) was listed as Least Concern, on the basis that it did not approach the thresholds for listing as Vulnerable under any criteria. The pre-split species was characterised as common or fairly common to abundant in most of its considerable former range (Boles 2016). The only density estimate for the pre-split species is from the Brown River catchment in New Guinea: species on smaller islands frequently occur at much higher densities so the population estimates provided here are considered likely to be biased low, hence precautionary in this context. The species occurs in a range of forested habitats and often in more open areas such as ecotones between forest types, natural clearings, secondary growth, cultivated areas with some trees and open scrub (Boles 2016).

R. kordensis Biak Fantail, is only found on the dual island of Biak-Supiori in Geelvink Bay, northwest New Guinea. A calculated Extent of Occurrence (EOO) for the species is 6,100km2, but the area of the two islands (it is apparently absent from Numfor [Pratt and Beehler 2015]) on which it occurs is approximately 3000km2. Although Biak-Supiori is two islands, the minimal distance between the islands (separated only by a mangrove bordered channel) suggests that it is best to treat the species as being comprised of a single subpopulation, particularly as the species is noted to use mangrove. Forest on Biak is under heavy threat from logging and subsistence farming, but there are areas of forest remaining in the north and especially in interior Supiori, and the species is assumed to be present in the 110km2 Biak-Utara protected area, which comprises virtually impenetrable forested limestone areas (Dekker et al. 2000, Bishop 1982 in Stattersfield et al. 1998, Wikramanayake et al. 2002). A great deal of the forest clearance on Biak took place during the last century however, with the suggestion that further large scale logging is presently not economically feasible (Wikramanayake et al. 2002). Given an assumed generation length of 5.5 years, it is now considered unlikely that declines in the area of habitat are likely to exceed the thresholds for listing under inferred population reduction (category A). However, a slow decline is suspected to be occurring owing to on-going habitat destruction.

It is mentioned that on this island the taxon is more restricted to ‘deep secondary growth and original forest near mangrove swamp’ (Boles 2016). This suggests a lower tolerance of modified habitats than reported for other taxa in the previously combined group and potentially a much small area of occupancy. In combination with the large proportion of habitat modification and loss that has previously taken place on Biak, it would suggest that this species is of greater concern than the others. However recent bird tour groups have observed the species regularly on the island (e.g. Hutchinson 2008), suggesting that it is not exceedingly rare.

The population is estimated to number 10,000-19,999 individuals based 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 6,667-13,333 mature individuals, rounded here to 6,000-15,000 mature individuals.

It is suggested that R. kordensis is listed as Near Threatened, on the basis that it approaches the thresholds for Vulnerable under criterion C2a(ii).

R. isura, R. assimilis, R. cinerea, R. obiensis, R. hoedti, R. rufiventris are all suggest to be listed as Least Concern, as they are not suspected of approaching the thresholds for listing as Vulnerable under any criteria.

R. isura, R. cinerea and R. rufiventris have ranges in excess of the thresholds for the geographic range criterion and are considered very likely to have fairly large populations.

R. assimilis is found on Watubela Island, Tayandu Island and the two Kai Islands in the South Moluccas, with an EOO calculated at 15,900 km2, within which the island area is approximately 1700km2. There is no evidence of a population decline, although recently the rate of habitat loss on Kai Kecil has been rapid, at roughly 10% within the past 15 years (data from Hansen et al. 2013). Owing to the species use of secondary and degraded habitat elsewhere in its range, this cannot necessarily be used to infer a population decline. The population is estimated to number 10,000-19,999 individuals based 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 6,667-13,333 mature individuals, rounded here to 6,000-15,000 mature individuals. If there was evidence of a decline or a particular dependency on intact forest such that a decline could be inferred from habitat loss within the range, the species would approach the thresholds for listing as Vulnerable under criterion C2a(i), but only if each subpopulation does not exceed 1,000 mature individuals. Given the caveat that the population could well be higher than this (based on the density estimate used), the largest subpopulation likely exceeds this considerably. Hence the species is considered Least Concern, unless there is evidence for a considerably smaller overall population and small subpopulations.

R. hoedti is found on Romang, Damar, Leti, Moa and Sermata, with an extent of occurrence calculated as 18,400 km2, with the area of the islands totalling approximately 1,000 km2. Within this limited range it is considered generally common, and is not thought to be declining. As with R. assimilis, the population is estimated to fall in the band 10,000-19,999 individuals based the same assessment. Similarly, if there was evidence of an ongoing population decline, then the species may approach the thresholds for listing as Vulnerable under criterion C2a(i), but only if the largest population consists of fewer than 1,000 mature individuals. This species is therefore also proposed to be Least Concern.

R. obiensis, which is found on Obi and Bisa in the North Moluccas, and R. bouruensis, on Buru, have small, restricted ranges with EOOs calculated at 3,640 km2 and 10,005 km2 respectively. Similarly R. tenkatei, restricted to Roti Island, off south west Timor in the Lesser Sundas has an EOO of 2,530 km2.

The population of R. obiensis is estimated to fall in the band 10,000-19,999 individuals based a similar assessment to that above. This estimate is equivalent to 6,667-13,333 mature individuals, rounded here to 6,000-15,000 mature individuals. Similarly, if there was evidence of an ongoing population decline, then the species may approach the thresholds for listing as Vulnerable under criterion C2a(i), but only if the largest population consists of fewer than 1,000 mature individuals. Obi Fantail R. obiensis is therefore also proposed to be Least Concern.

R. tentakei described as frequent in all wooded habitats on Roti including villages (Trainor 2005) is estimated, using the same approach, to have a population in a band of between 10,000-19,999 individuals. This estimate is equivalent to 6,667-13,333 mature individuals, rounded here to 6,000-15,000 mature individuals. If there was evidence of an ongoing population decline then the species may approach the thresholds for listing as Vulnerable under criterion C2a(ii). However, as the population estimate is considered precautionary and there is no evidence of a population decline, the suggestion is to list Roti Fantail R. tenkatei as Least Concern.

The population of R. bouruensis is estimated to fall in the band 20,000-49,999 individuals based a similar assessment to that above. Buru Fantail R. bouruensis is proposed to be listed as Least Concern.

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

*Note that the term ‘location’ defines a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present. The size of the location depends on the area covered by the threatening event and may include part of one or many subpopulations. Where a taxon is affected by more than one threatening event, location should be defined by considering the most serious plausible threat (IUCN 2001, 2012).

References:

Boles, W. (2016). Northern Fantail (Rhipidura rufiventris). 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 http://www.hbw.com/node/59178 on 6 October 2016).

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 on-line from: http://earthenginepartners.appspot.com/science-2013-global-forest. Accessed through Global Forest Watch on [date]. www.globalforestwatch.org

Hutchinson, R. 2008. West Papua (Irian Jaya) July 2008. BirdtourAsia tour report. http://www.birdtourasia.com/pdf%20Reports/Birdtour%20Asia%20West%20Papua%202008.pdf

IUCN. 2001. IUCN Red List Categories and Criteria: Version 3.1. Gland, Switzerland and Cambridge, UK: IUCN Species Survival Commission.

IUCN. 2012. Guidelines for Application of IUCN Red List Criteria at Regional and National Levels: Version 4.0. Gland, Switzerland and Cambridge, UK: IUCN.

Pratt, T.K. and Beehler, B.M. 2015. Birds of New Guinea. Second Edition. Princeton University Press, Princeton and Oxford.

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.

Trainor, C. R. 2005. Birds of Tapuafu peninsula, Roti island, Lesser Sundas, Indonesia. Forktail 21: 121-131.

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4 Responses to Archived 2016 topics: Northern Fantail (Rhipidura rufiventris) is being split: list R. kordensis as Near Threatened?

  1. Guy Dutson says:

    R. kordensis is relatively common and tolerant of degraded habitats on Biak

  2. James Eaton says:

    All the Indonesia taxa are widespread and common throughout secondary and primary habitats, with the exception of Seram Fantail which appears to be highly localised in lowland habitats on Boano, Ambon and Seram (I have not seen it on four visits to Seram for example), so perhaps further study required with this species regarding a proposed higher uplisting to Near Threatened.

  3. Rob Martin (BirdLife International) says:

    Marsden (1997) recorded only a single individual of the pre-split species from 65 census stations in lowland unlogged forest on Seram. However there are scattered records throughout lowland Seram, so even if at low density the population may still be relatively large as large contiguous areas of forest were noted to still exist on Seram in the late 1990s (Wikramamayake 2002) and rates of deforestation since then have been low relative to other parts of the Moluccas (data from Hansen et al. 2013: citation above). As such, and with subpopulations present on Boano and Ambon, it is unlikely that the species presently approaches any of the thresholds for listing as Vulnerable.

    Marsden, 1997. Changes in bird abundance following selective logging on Seram, Indonesia. Conservation Biology 12: 605-611.

  4. Rob Martin (BirdLife International) says:

    Preliminary proposals

    Based on available information, our preliminary proposal for the 2016 Red List would be to list all the resultant taxa from this split as Least Concern, including R. kordensis.

    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 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.