Archived 2020 topic: Namuli Apalis (Apalis lynesi): revise global status?

BirdLife International factsheet for Namuli Apalis.

Namuli Apalis is endemic to Mozambique, and found at two sites: Mt Namuli and Mt Mabu. The species prefers low-canopy montane forest and rich shrubland (Dowsett-Lemaire, 2010). On Namuli, it was found at altitudes between 1,270m and 1,900m, while on Mabu it was only found above 1,380m. Studies in 2007/2008 found that Namuli offered 13 km² of suitable habitat, while Mabu provided 8 km² (Dowsett-Lemaire, 2010). The population estimate of 10,000-19,999 suggested by Ryan et al. (1999) is now thought to be unrealistic. New population density estimates made by (Dowsett-Lemaire, 2010) estimated a minimum population in 2007/2008 of 600-700 pairs on Namuli, based on density estimates of five pairs per 10 ha over an area of 1,200-1,400 ha. On Mabu, the Namuli Apalis was found to be much rarer, with an estimated few dozen pairs in the 800 ha.

The main threat to Namuli Apalis is habitat loss through deforestation for potato cash crops. This threat has become significantly worse in the last 10 years, and the rate of deforestation is continuing at unsustainable levels (Timberlake, 2017). The species has been considered Near Threatened, approaching globally threatened status under Criterion B1ab(i,ii,iii,v)+2ab(i,ii,iii,v) (BirdLife International, 2020). However, this is no longer tenable due to the increasing rate of deforestation, which may exceed the current thresholds and result in the species being unable to retain its current Red List Category. We have therefore reviewed this species here against all the criteria.

Criterion A: The population trend for this species has not been directly quantified. The rate of decline is measured over the longer of ten years or three generation lengths of the species. The generation length for the Namuli Apalis has been recalculated to 2.6 years (Bird et al., 2020)*. Rates of decline for this species are therefore calculated over ten years.  

The main threat to Namuli Apalis is deforestation. It is estimated that 3-5 km² of the total area of habitat (13 km²) habitat remains on Namuli, while the 8 km² at Mabu remains undisturbed (F. Dowsett-Lemaire pers. comm., 2020). This equates to a reduction in total habitat of 38-47% between 2007 and 2017. Assuming that the population declines at the same rate as tree cover, this meets the threshold for Vulnerable (a population reduction >30% over the longer of 10 years or three generations). Namuli Apalis may be listed as Vulnerable under Criterion A2c.

Criterion B: The Extent of Occurrence (EOO) for Namuli Apalis is believed to be 1,700km² (BirdLife International, 2017). This reaches the initial threshold (EOO <5,000 km²) for Endangered under Criterion B1.

Namuli Apalis is not thought to be severely fragmented as remaining forest patches are quite close together (Timberlake, 2017), and it can tolerate some habitat disturbance (Ryan, 2020).However, it is believed to only exist at a few locations. Location in this instance is defined as a geographically distinct area where a single development threat can rapidly eliminate or severely reduce a population within the longer of a single generation or three years (IUCN Standards and Petitions Committee, 2019). The recalculated generation length for Namuli Apalis is now 2.6 years (Bird et al., 2020)*, so in this case, the reduction is measured over three years. The forests of Namuli have suffered extensive conversion to potato cash crop plantations, with an overall estimated habitat loss of 8-10 km² between 2007 and 2017 (based on estimated figures of 3-5 km² remaining from 13 km²; F. Dowsett-Lemaire pers. comm., 2020). Assuming that the reduction rate was steady throughout, this equates to a loss rate of roughly 2.4-3 km² every 3 years. At the current estimated loss rate, the remaining habitat would be destroyed within six years, and there is additional evidence to suggest that the deforestation rate is increasing (Timberlake, 2017). Therefore, the number of locations on Namuli is estimated to be two. The forest on Mabu is currently undisturbed, but if the same threat was to spread there, the area would equate to three locations. Therefore, the total number of locations for the Namuli Apalis is estimated to be five, which meets the threshold (locations ≤ 5) for classification as Endangered. The Namuli Apalis may be listed as Endangered under Criterion B1ab(i,ii,iii,v).

Criterion C: No recent population observations have been made. However, the remaining suitable habitat on Namuli is estimated to be between 3km² and 5km² (300-500 ha) (F. Dowsett-Lemaire, pers. comm., 2020), and the population density of Namuli Apalis on Namuli was estimated to be five pairs per 10 ha (Dowsett-Lemaire, 2010). Therefore, the population on Namuli may now be an estimated 150-250 pairs, or 300-500 mature individuals. Assuming the population densities are the same on Mabu, with 800 ha of suitable habitat, this would equate to an additional 400 pairs, and a total of 300-1,300 mature individuals. However, the forest on Mabu is believed to be sub-optimal for this species, and Dowsett-Lemaire (2010)found vastly different population densities at the two sites. It is therefore likely that the current population is nearer the lower estimate. A population estimate of 300-1,300 mature individuals with an inferred continuing decline through habitat loss meets the initial threshold for classification as Endangered under Criterion C. In order to fully meet this classification, other sub-criteria must be met.

Based on the population size estimate, the number of mature individuals in each subpopulation is estimated to be <1,000, which, alongside the number of mature individuals at <10,000, meets the threshold for classification as Vulnerable. Namuli Apalis may be listed as Vulnerable under Criterion C2a(i).

Criterion D: The global population is estimated to be 300-1,300 individuals. On the assumption that the true population size is nearer the lower estimate, the Namuli Apalis may be listed as Vulnerable under Criterion D1.

Criterion E: To the best of our knowledge, no quantitative analysis has been performed for this species, so it cannot be assessed against this criterion.

This species reached the threshold for a genuine change in Red List Category in c. 2017. Therefore, it is suggested that Namuli Apalis (Apalis lynesi) be listed as Endangered under Criterion B1ab(i,ii,iii,v) We welcome any comments to the proposed listing.

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 and the information requested. By submitting a comment, you confirm that you agree to the Comment Policy.

*Bird generation lengths are estimated using the methodology of Bird et al. (2020), as applied to parameter values updated for use in each IUCN Red List for birds reassessment cycle. Values used for the current assessment are available on request. We encourage people to contact us with additional or improved values for the following parameters; adult survival (true survival accounting for dispersal derived from an apparently stable population); mean age at first breeding; and maximum longevity (i.e. the biological maximum, hence values from captive individuals are acceptable).

An information booklet on the Red List Categories and Criteria can be downloaded here and 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.

References

BirdLife International 2017., Apalis lynesiThe IUCN Red List of Threatened Species 2017: e.T22713724A118640011. https://dx.doi.org/10.2305/IUCN.UK.2017-3.RLTS.T22713724A118640011.en. Downloaded on 23 March 2020.

BirdLife International, 2020, Species factsheet: Apalis lynesi. Downloaded from http://www.BirdLife.org on 23/03/2020

Dowsett-Lemaire, F., 2010, Further ornithological exploration of Namuli and Mabu Mountains (northern Mozambique), and the urgent need to conserve their forests, Bulletin African Bird Club, Vol 17, No 2, pp 161-162, 168.

IUCN Standards and Petitions Committee, 2019. Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Committee. Downloadable from http://www.iucnredlist.org/documents/RedListGuidelines.pdf.

Ryan, P. G.; Bento, C.; Cohen, C.; Graham, J.; Parker, V.; Spottiswoode, C., 1999. The avifauna and conservation status of the Namuli Massif, northern Mozambique. Bird Conservation International 9: 315-331.

Ryan, P., 2020. Namuli Apalis (Apalis lynesi). 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 https://www.hbw.com/node/58661 on 23 March 2020).

Timberlake, J., 2017, Mt Namuli ‒ a conservation update, report for Legado, Mozambique, Unpublished report.

Tracewski, Ł.; Butchart, S. H. M.; Di Marco, M.; Ficetola, G. F.; Rondinini, C.; Symes, A.; Wheatley, H.; Beresford, A. E.; Buchanan, G. M., 2016. Toward quantification of the impact of 21st-century deforestation on the extinction risk of terrestrial vertebrates. Conservation Biology 30: 1070-1079.

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3 Responses to Archived 2020 topic: Namuli Apalis (Apalis lynesi): revise global status?

  1. Red List Team (BirdLife International) says:

    The window for consultation is now closed. We will analyse and interpret the new information and post a preliminary decision on this species’s Red List status on this page in early July.

    Thank you,
    BirdLife Red List Team

  2. Red List Team (BirdLife International) says:

    Preliminary proposal

    Based on available information, our preliminary proposal for the 2020 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 in mid-July, 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 2020 Red List categories will be published on the BirdLife and IUCN websites in December 2020/January 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN. The final publication date will be publicised by IUCN here: https://www.iucnredlist.org/assessment/updates

  3. Red List Team (BirdLife International) says:

    Recommended categorisation to be put forward to IUCN

    The final categorisation for this species has not changed. Namuli Apalis is recommended to be listed as Endangered under Criterion B1ab(i,ii,iii,v).

    Many thanks for everyone who contributed to the 2020 GTB Forum process. The final 2020 Red List categories will be published on the BirdLife and IUCN websites in December 2020/January 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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