Turner’s Eremomela (Eremomela turneri): revise global status?
Posted on May 23, 2019 by Red List Team (BirdLife International)
BirdLife species factsheet for Turner’s Eremomela: http://datazone.birdlife.org/species/factsheet/turners-eremomela-eremomela-turneri

Turner’s Eremomela (Eremomela turneri) is a poorly known species with a potentially very patchy distribution. Comprising two subspecies, the nominate is relatively common in Kakamega and South Nandi Forests, Kenya, the latter being the species’s stronghold (Kosgey 2013). Additionally, there has been a recent record from North Nandi Forest (Bett et al. 2016), and there are historical records from the Yala River, and an unconfirmed record from south of Mt. Elgon (van Someron 1920). The other subspecies, kalindei, now appears to be found only at a small number of localities in east-central Democratic Republic of Congo in the south-eastern corner of the equatorial belt (Prigogine 1958), although there are historical records from north-eastern Democratic Republic of Congo and the extreme south-west of Uganda (Chapin 1953). The species occurs in lowland to mid-altitude forest, in the canopy of large trees (Prigogine 1958, Kosgey 2013), appearing to favour slightly more open areas such as along streams, forest edges, clearings and secondary growth (Prigogine 1958, Pearson and de Juana 2018), although it does sometimes occur in primary forest (Pearson and de Juana 2018).

The major threat to the species is habitat loss, with the encroachment of forests by cultivation, charcoal making, cattle grazing and commercial logging all potentially having had an effect on forest structure in at least the Kenyan part of its range (Bennun and Njoroge 1999). Given these threats, and the fact it appears to have a restricted range within its patchy distribution the species has been considered Endangered under Criterion B1ab(i,ii,iii,iv,v) (see BirdLife International 2018). However, this is no longer tenable because this was based on an Extent of Occurrence (EOO) value calculated as the ‘area of mapped range’. This is no longer appropriate and the EOO should be calculated using a Minimum Convex Polygon (see IUCN 2001, 2012, Joppa et al. 2016), as EOO is a measure of the spatial spread of areas occupied by a species, not the actual area it occupies. The resulting EOO value now exceeds the thresholds required to maintain the species’s current listing, and as such it potentially cannot retain its current Red List status. Therefore, we have fully reviewed the species here against all criteria.

The initial topic on this analysis can be found here.

Criterion A – Deforestation data between 2000 and 2012 from Tracewski et al. (2016) suggests that over three generations (10.8 years) the species may have lost only 0.42% of its habitat. However, this is based on its currently mapped range, which is not accurate and has been redrawn. The rates of forest loss in the areas that should be included in the map could well increase this value (see Global Forest Watch 2018), and the species can be inferred to be in decline. But the overall rate of decline, if proportional to habitat loss, is still likely to be far below the threshold for listing as Vulnerable (30% over three generations), and the species is assessed as Least Concern under this criterion.

Criterion B – The new EOO value using a Minimum Convex Polygon is c.39,400 km2, while the Area of Occupancy (AOO) value is 1,400 km2. The EOO value exceeds the thresholds for listing as Vulnerable under Criterion B1 (< 20,000 km2), yet the AOO value meets the threshold for Vulnerable (< 2,000 km2). The species’s range can be at least classed as fragmented (potentially severely so) and the number of locations* could be as low as 6-10 if a sighting locality equates to a location, but given that the main threat is from habitat loss then the number of locations may be larger than this (although still fairly small). Ongoing declines in forest area and inferred declines in the population size mean that the species meets sufficient conditions to warrant listing at least as Near Threatened, approaching the threshold for listing as threatened under Criterion B2ab(i,ii,iii,v),and potentially as Vulnerable. While there have likely been historical losses of locations, it is unsure whether these are continuing and so condition b(iv) is not included in the proposed criteria string.

Criterion C – The population in South Nandi Forest has been estimated at c.13,900 to c.14,400 individuals (Otieno et al. 2011, Kosgey 2013), while that in Kakamega has been estimated at c.4,300 individuals. There has been no estimation of the populations in North Nandi Forest or in Democratic Republic of Congo, but the overall population has been placed in the range 20,000-49,999 individuals. This roughly equates to 13,000-34,000 mature individuals. At the lower end of this estimate, the population size may approach the threshold for Vulnerable under this criterion, but further conditions would need to be met to warrant a listing as Near Threatened.

There has been no accurate quantification of the rate of decline, so Criterion C1 cannot be used. To the best of our knowledge, the species does not undergo extreme fluctuations; so it cannot be listed under Criterion C2b either. With the species occurring in several subpopulations, the largest of these would need to contain fewer than 1,000 mature individuals (or a number approaching this) to warrant listing under Criterion C2a(i). However, given that the population in South Nandi alone is thought to contain >10,000 individuals, the species would not warrant listing under C2a(i), and so overall the species is assessed as Least Concern under Criterion C.

Criterion D – The species’s population size is too large to warrant listing under this criterion. While it is potentially restricted to only a very limited number of locations, at the moment the ongoing threats do not appear to be great enough to drive the species to Critically Endangered or Extinct within a very short period of time. Therefore, the species likely does not warrant listing under this criterion, but very precautionarily it could warrant listing as Near Threatened under Criterion D2.

Criterion E – To the best of our knowledge, there has been no quantitative assessment of extinction risk conducted for this species. Therefore, it cannot be assessed against this criterion.

Therefore, it appears that this species warrants listing as at least as Near Threatened, approaching the threshold for listing as threatened under Criterion B2ab(i,ii,iii,v) and potentially under Criterion D2 too. Comments are welcome on this proposal, but please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of the species’ Red List status. Therefore, please make sure your comments are relevant to the species’ Red List status.

*The term ‘location’ refers to a distinct area in which a single threatening event can rapidly affect all individuals of the taxon present, with the size of the location depending on the area covered by the threatening event. 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).

An information booklet on the Red List Categories and Criteria can be downloaded hereand the Red List Criteria Summary Sheet can be downloaded here. Detailed guidance on IUCN Red List terms and definitions and the application of the Red List Categories and Criteria can be downloaded here.
This entry was posted in Africa and tagged Democratic Republic of Congo, Kenya, Turner's Eremomela, Uganda. Bookmark the permalink.
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1 Response to Turner’s Eremomela (Eremomela turneri): revise global status?
   
   - James Bradley says:May 31, 2019 at 4:01 pm