A Review of the Red List Status of Endemic Birds of São Tomé and Príncipe

São Tomé and Príncipe is an island nation in the Gulf of Guinea, with each of its main two islands listed as separate Endemic Bird Areas (BirdLife International 2018b,c). The country’s native birds include 14 globally threatened species (16% of the avian diversity native to the islands) (BirdLife International 2018a). Twelve of these are endemic to the country and a further two endemic species are listed as Near Threatened. Therefore 50% of the endemic species of São Tomé and Príncipe are currently listed as Near Threatened or worse.

During our open call for potential topics R. F. de Lima (in litt. 2018) proposed several changes to the Red List status of the endemic species of São Tomé and Príncipe. We have, therefore, reviewed the entire endemic avifauna of the country (plus Sao Tome Bronze-naped Pigeon, Columba malherbi, which only occurs in this country and on the island of Annobón, Equatorial Guinea) to find inconsistencies in the current application of Red List criteria.

From this review, seven species were found to potentially warrant a change in Red List category. Each of these have their own individual topic to discuss any potential changes in Red List status, which can be found here:

Giant Sunbird (Dreptes thomensis)

Giant Weaver (Ploceus grandis)

Principe Speirops (Zosterops leucophaeus)

Principe White-eye (Zosterops ficedulinus)

Sao Tome Green-pigeon (Treron sanctithomae)

Sao Tome Thrush (Turdus olivaceofuscus)

Sao Tome White-eye (Zosterops feae)

 

To make sure that your comments are taken into account, if you have any comments or further information regarding these species please post them on their respective topics and not at the bottom of this one.

 

Of those Red List category changes proposed by R. F. de Lima (in litt. 2018), two were not considered to qualify for revision; the Critically Endangered Newton’s Fiscal (Lanius newtoni) and Sao Tome Grosbeak (Crithagra concolor), which were both proposed to be downlisted to Endangered as a result of de Lima et al. (2017).

De Lima et al. (2017) suggested that both species have population sizes in excess of 50 mature individuals (de Lima et al. 2017), and so may be eligible for downlisting. However, the Red List accounts for both species (BirdLife International 2018d,e) do already take into account the fact that the population sizes are >50 mature individuals; but at the moment there is insufficient evidence to say that their population sizes are >250 mature individuals. As both are considered to be undergoing continuing declines they, therefore, do still meet the threshold for listing as Critically Endangered under criterion C2a(ii).

Other species will not be discussed in their own specific topics as their global status in unchanged. However a number of potential criteria changes were identified so we provide, below, the list of the other species assessed with a summary of proposed criteria changes.

 

Sao Tome Olive-pigeon (Columba thomensis) – currently Endangered under criteria B1ab(ii,v); C2a(ii). Proposed change to Endangered under criteria B1ab(ii,iii,v)+B2ab(ii,iii,v); C2a(ii).

Sao Tome Bronze-naped Pigeon (Columba malherbi) – currently Near Threatened under criteria A2cd+3cd. Proposed change to Near Threatened under criteria A2cd+3cd+4cd; B1ab(iii,v); C2a(i).

Sao Tome Spinetail (Zoonavena thomensis) – retain as Least Concern.

Dwarf Ibis (Bostrychia bocagei) – currently Critically Endangered under criterion C2a(ii). This may be retained, or could be changed to Critically Endangered under criteria B1ab(iii,v); C2a(ii).

Sao Tome Scops-owl (Otus hartlaubi) – retain as Vulnerable under criterion D1.

Sao Tome Kingfisher (Corythornis thomensis) – retain as Least Concern.

Principe Kingfisher (Corythornis nais) – retain as Least Concern.

Sao Tome Oriole (Oriolus crassirostris) – currently Vulnerable under criterion D1. Proposed change to Vulnerable under criterion C2a(ii).

Sao Tome Paradise-flycatcher (Terpsiphone atrochalybeia) – retain as Least Concern.

Newton’s Fiscal (Lanius newtoni) – retain as Critically Endangered under criterion C2a(ii).

Sao Tome Prinia (Prinia molleri) – retain as Least Concern.

Dohrn’s Warbler (Sylvia dohrni) – retain as Least Concern.

Black-capped Speirops (Zosterops lugubris) – retain as Least Concern.

Principe Starling (Lamprotornis ornatus) – retain as Least Concern.

Principe Thrush (Turdus xanthorhynchus) – currently Critically Endangered under criteria B1ab(ii,iii,v); C2a(ii). Retain this criteria string, or change to Critically Endangered under only criterion C2a(ii).

Principe Sunbird (Anabathmis hartlaubii) – retain as Least Concern.

Newton’s Sunbird (Anabathmis newtoni) – retain as Least Concern.

Principe Golden Weaver (Ploceus principes) – retain as Least Concern.

Sao Tome Weaver (Ploceus sanctithomae) – retain as Least Concern.

Sao Tome Short-tail (Amaurocichla bocagii) – retain as Vulnerable under criterion D1.

Principe Seedeater (Crithagra rufobrunnea) – retain as Least Concern.

Sao Tome Grosbeak (Crithagra concolor) – currently Critically Endangered under criteria B1ab(ii,iii,v); C2a(ii). Proposed change to Critically Endangered under only criterion C2a(ii).

 

Further information regarding IUCN Red List Categories and Criteria can be found here, and further details can be posted in the comments section upon request.

 

Comments are welcome on these species, in particular if there are any comments with information on the number of locations (as defined under the IUCN guidance [IUCN 2012]) for Dwarf Ibis and Principe Thrush. Please do, though, make sure that comments are relevant to the Red List status of the species as this space is not a general discussion regarding the ecology of the species.

 

References

BirdLife International, 2018a. Country profile: São Tomé e Príncipe. Available from http://www.birdlife.org/datazone/country/sao-tome. Checked: 2018-02-27

BirdLife International. 2018b. Endemic Bird Areas factsheet: Príncipe. Downloaded from http://www.birdlife.org on 27/02/2018.

BirdLife International. 2018c. Endemic Bird Areas factsheet: São Tomé. Downloaded from http://www.birdlife.org on 27/02/2018.

BirdLife International. 2018d. Species factsheet: Lanius newtoni. Downloaded from http://www.birdlife.org on 27/02/2018.

BirdLife International. 2018e Species factsheet: Crithagra concolor. Downloaded from http://www.birdlife.org on 27/02/2018.

IUCN. 2012. IUCN Red List Categories and Criteria: Version 3.1. Second edition. IUCN, Gland, Switzerland and Cambridge, UK.

de Lima, R.; Dunn, J.; Cabinda, G.; Fonseca, R.; Oquiongo, G.; Oquiongo, J.; Samba, S.; Santana, A.; Soares, E.; Viegas, L.; Ward-Francis, A.; T. Costa, L.; Palmeirim, J.; Buchanan, G. 2017. Distribution and habitat associations of the critically endangered bird species of São Tomé Island (Gulf of Guinea). Bird Conservation International 27(4): 455-469.

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7 Responses to A Review of the Red List Status of Endemic Birds of São Tomé and Príncipe

  1. Graeme Buchanan says:

    Thank you for the clarification, and as the status suggestions sound appropriate I support them. As more information is likely to be coming in on these species soon it will be important to keep these species under close review.

  2. Ricardo Faustino de Lima says:

    First, thank you for opening this discussion. There is plenty of new information regarding most of STP endemic bird species, so it is very timely to review their Red List status and ensure that they are applied consistently across species.

    I agree with all proposed category changes and have only a few comments regarding the criteria.

    The Dwarf Ibis should be maintained as CR using criteria B1ab(iii,v);C2a(ii). Based mostly on information obtained from hunters (Sampaio et al. 2016), it seems very reasonable to assume that this species is under intensive hunting pressure that has and will continue to affect distribution and population size. Based on IUCN’s definition of location, this means that the whole species constitutes a single location, and that the distribution-based criteria (B) would trigger CR status (55sqkm – based on Soares 2017). Criteria C also seem to classify this species as CR: Even though it seems likely that the population might be far larger than previously assumed (Azevedo 2015), so are extraction levels (Sampaio et al. 2016), and precautionary population estimates based on updated AOO (55sqkm – based on Soares 2017) do not exclude the possibility that the population is smaller than 250 mature individuals (min. 191 individuals in total, using intensive survey methods – Azevedo 2015).

    The Principe Thrush should be classified as CR using criteria B1ab(ii,iii,v);C2a(ii). Hunting is threatening this species (BirdLife International 2014). Therefore, I suggest it is recognized as occurring on a single location, based on IUCN definition of location and that the distribution-based criteria (B) is kept. Even though there is no evidence-based population size estimate for this species, the population size criteria(C) should also be kept, as a precautionary measure. This species is scarce even within its tiny distribution area (Dallimer et al. 2012; BirdLife International 2018). BirdLife International São Tomé and Príncipe Initiative’s database has compiled all recent observations of this species and suggests that it might even be absent from significant portions of its recognized EOO (Dallimer et al. 2012; BirdLife International 2018).

    The Sao Tome Bronze-naped Pigeon might best be maintained as NT using the criteria A2cd+3cd+4cd;B1ab(iii,v)c(ii,iv), since there is strong indications for population fluctuations in São Tomé Island (Carvalho et al. 2015). These might be linked to seasonal movements, changes in detectability or actual changes in abundance linked to hunting pressure, but until the source of such fluctuations is clarified, as precaution, it might be best to consider them a potential threat factor. I also suggest abandoning criterium C2a(i), since the population on São Tomé Island alone seems to be well above the threshold of 10,000 mature individuals (min. 47.846 individuals in total – Carvalho 2015).

    Finally, the Sao Tome Scops-owl, Oriole and Short-tail might warrant becoming EN if there is any significant loss on forest area or quality. This would follow criteria B1ab(iii,iv,v)+2ab(iii,iv,v), since all of them are heavily reliant on well-preserved forest ecosystems and have AOO < 500 sqkm (437, 320 and 176 sqkm, respectively – based on Soares 2017).

    Best regards,

    References:
    Azevedo, F. (2015) How many dwarf olive ibises Bostrychia bocagei are there in São Tomé? Using distance sampling and plot sampling to estimate population of a critically endangered endemic bird. MSc thesis. Évora University, Portugal. (https://dspace.uevora.pt/rdpc/bitstream/10174/16421/1/Francisco_P._Azevedo_Dissertação_MBC_Versão_Final_Oficial.pdf)

    BirdLife International (2014) Single Species Action Plan for the conservation of the Príncipe Thrush Turdus xanthorhynchus. Cambridge, UK.

    BirdLife International (2018) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 27/06/2018.

    Carvalho, M., J. Fa, F. Rego, R.F. de Lima, G. Santos & J. Palmeirim (2015) Factors influencing the distribution and abundance of endemic pigeons in São Tomé Island (Gulf of Guinea) Bird Conservation International 25: 71-86.

    Carvalho, M. (2015) Hunting and conservation of forest pigeons in São Tomé (West Africa). PhD thesis. Lisbon University, Portugal. (https://www.repository.utl.pt/handle/10400.5/9265?locale=en)

    Dallimer, M., M. Parnell, J.E. Bicknell & M. Melo (2012) The importance of novel and agricultural habitats for the avifauna of an oceanic island. Journal for Nature Conservation 20(4): 191-199.

    Sampaio, H.A.L., R.F. de Lima, R. da Fonseca, G.C. Cabinda, G. Oquiongo, A. Ward-Francis & S.J. Havery (2016) Hunters and the Critically Endangered Dwarf Olive Ibis Bostrychia bocagei, endemic to São Tomé Island. Unpublished report.

    Soares, F. (2017) Modelling the distribution of São Tomé bird species: Ecological determinants and conservation prioritization. MSc thesis, Lisbon University, Portugal. (http://repositorio.ul.pt/handle/10451/30776).

  3. Ricardo Faustino de Lima says:

    As a summary of these assessments, and to ensure consistency in the application of criteria, please find below a list of the non-LC endemic bird species of STP by decreasing order of threat:
    Dwarf Ibis (CR)
    Principe Thrush (CR)
    Newton’s Fiscal (CR)
    Sao Tome Grosbeak (CR)
    Sao Tome Olive-pigeon (EN)
    Principe White-eye (EN)
    Sao Tome Green-pigeon (EN/VU)
    Sao Tome Short-tail (VU)
    Giant Sunbird (VU)
    Sao Tome Scops-owl (VU)
    Sao Tome Oriole (VU)
    Sao Tome Bronze-naped Pigeon (NT)
    Giant Weaver (NT)
    Sao Tome White-eye (NT)

  4. Filipa Coutinho Soares says:

    Primarily, I want to thank you for this open discussion.
    I mainly want to add information about the data of my MSc thesis, thus helping to clarify what kind of data was taken into account for the estimated areas described above by R. F. de Lima. In my thesis, I included both systematic (2398) and occasional observations (677), which can sometimes inflate the number of records of rarer species (Soares 2017). Finally, the data used to estimate the areas and the frequency refered by R. F. de Lima, only considered systematic observations.

    Soares, F. (2017) Modelling the distribution of São Tomé bird species: Ecological determinants and conservation prioritization. MSc thesis, Lisbon University, Portugal. (http://repositorio.ul.pt/handle/10451/30776).

    Best regards

  5. Jorge Palmeirim says:

    I can not add much to the very well-informed contribution of Ricardo Lima. However, it may be worth pointing out that the population of Sao Tome e Principe is growing very fast, which is reflected in an increasing pressure on forest resources. Although up to now most of the pressure is on areas of secondary forest, some of those are highly valuable for a number of endemic bird species. Moreover, secondary forest plays a very important role as a buffer for the remaining native forest. Consequently, it seems important to take into consideration that the quality and extent of habitat for forest species is going to decline in the next few years, and that this may justify a revision of the status of some species in a not so distant future.

  6. James Westrip (BirdLife) says:

    Preliminary proposals

    Decisions for species with their own individual topics are outlined in those specific topics.

    Regarding the other species in this topic; based on available information, our preliminary proposal for the 2018 Red List would be to list the majority of the species under the proposed criteria outlined above.

    The species where there are some differences are;

    Sao Tome Bronze-naped Pigeon as Near Threatened under criteria A2cd+3cd+4cd; B1ab(iii,v).

    Dwarf Ibis as Critically Endangered under criterion C2a(ii), as the EOO as calculated using an MCP is >100km2.

    Principe Thrush as Critically Endangered under criteria B1ab(ii,iii,v); C2a(ii).

    Subcriterion c for criterion B cannot be used for Sao Tome Bronze-naped Pigeon as fluctuations need to be of an order of magnitude to be considered extreme per IUCN guidelines.

    With regards to the Scops-owl, Oriole and Short-tail, those range values provided would need to be confirmed as calculated using a 2x2km2 grid per IUCN guidelines to count as an AOO. Additionally, data from deforestation analyses by Tracewski et al. (2016) suggest the area of impact with the species’s ranges is very small and so the number of locations where they are found would be far too large to meet the threshold for listing under criterion B.

    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 the initial proposal.

    The final 2018 Red List categories will be published on the BirdLife and IUCN websites in November, following further checking of information relevant to the assessments by both BirdLife and IUCN.

    References:
    IUCN Standards and Petitions Subcommittee. 2017. Guidelines for Using the IUCN Red List Categories and Criteria. Version 13. Prepared by the Standards and Petitions Subcommittee. Downloadable from http://www.iucnredlist.org/documents/RedListGuidelines.pdf.

    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.

  7. Ricardo Faustino de Lima says:

    Thank you once again for promoting this discussion, which will provide a much needed update on the conservation status of São Tomé and Príncipe endemic bird species, based on the data that has collected over the past years.
    I’ve added my few minor comments on some of the revisions, but have nothing to add to this post, rather than showing my availability to make available the distribution and frequency data I have to improve the information currently available online, to further support the decisions that will come out of this discussion, and to promote an informed discussion on future reviews, namely concerning population trends.
    Best regards.

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