Archived 2020 topic: Serra do Mar Tyrannulet (Phylloscartes difficilis): revise global status?

BirdLife species factsheet for Serra do Mar Tyrannulet

Serra do Mar Tyrannulet (Phylloscartes difficilis) occurs in south-east Brazil (Espírito Santo and south Minas Gerais to north-east Rio Grande do Sul). It has a disjunct distribution and is found in the mountains of the Serra da Mantiqueira in the southeast of Minas Gerais, east of Rio de Janeiro, northeast of São Paulo and southwest of Espírito Santo, as well as in the Serra do Mar in the east of Paraná and northeast of Santa Catarina and in the Serra Geral in the southeast of Santa Catarina and northeast of Rio Grande do Sul (WikiAves 2018). It is resident in the lower growth of montane evergreen forest and edge (Ridgely and Tudor 1994, Parker et al. 1996).

The species is currently listed as Near Threatened because it was suspected to be declining moderately rapidly owing to habitat loss. However, recent remote-sensed data on forest loss suggests that the species’s population is unlikely to be declining as rapidly as previously thought. Hence, we are undertaking a review of the species’s Red List Category. Our current information on the species’s conservation status will now be compared to all Red List Criteria:

Criterion A – The generation length of Serra do Mar Tyrannulet has been estimated to be 2.26 years (Bird et al. 2020)*. Hence, the population reduction is here assessed over a period of ten years.

An analysis of forest loss from 2000-2012 found that forest was lost within the range at a rate equivalent to 3% over ten years (Tracewski et al. 2016). According to Global Forest Watch, 4020 km2 of tree cover was lost between 2008 and 2018 within the range, equivalent to a 4.3% decrease in tree cover (Global Forest Watch 2020). The population size is thus suspected to have declined by 1-9% over the past ten years.

Forest loss within the range was particularly high in 2016 (Global Forest Watch 2020), and if the average rate of deforestation within the range is projected over ten years, this would amount to a total loss of 6%. Higher rates of deforestation have been seen in 2019, at least in some parts of Brazil. Hence, over the next ten years, the population size is suspected to undergo a reduction of 5-15%. These suspected reductions do not approach the thresholds for listing the species as threatened under Criterion A. Serra do Mar Tyrannulet is therefore assessed as Least Concern under this criterion.

Criterion B – Based on a minimum convex polygon around the mapped range, the Extent of Occurrence (EOO) is estimated at 288,000 km2. This does not approach the threshold for listing the species as threatened under Criterion B1. TheArea of Occupancy (AOO) has not been quantified, but an analysis of remote-sensed data estimated 12,553 km2 of tree cover within the range in 2012 (Tracewski et al. 2016). The AOO is thus unlikely to approach the threshold for listing as threatened under Criterion B2 (< 2,000 km2). Serra do Mar Tyrannulet is assessed as Least Concern under Criterion B.

Criterion C – No survey data is available. The species has been described as infrequent and difficult to see (R. Amorin in litt. 2020). Based on the recorded population density of a congener (Phylloscartes virescens: 1.14 individuals/km2; Thiollay 1986), the area of tree cover with over 30% canopy cover within the range in 2010 (94,000 km2; Global Forest Watch 2020) and assuming that only 40-60% of forest is occupied, the population size is tentatively estimated at 42,864-64,296 individuals, roughly equating to 28,576-42,864 mature individuals. Since the species is described as infrequent, the population size is assumed to fall towards the lower end of the estimate and is here placed in the band 20,000-49,999 mature individuals. This number does not approach the threshold for listing the species as threatened under Criterion C. Serra do Mar Tyrannulet is therefore assessed as Least Concern under this criterion.

Criterion D – Based on the estimates described above, the population size does not meet or approach the threshold for Vulnerable under Criterion D1. The species does not have a restricted AOO of number of locations such that deforestation could drive it to Critically Endangered or Extinct within one generation. Serra do Mar does not therefore meet the criteria for listing as Vulnerable under Criterion D2. The species is therefore assessed as Least Concern under Criterion D.

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

Based on the above assessment, it is proposed to list the Serra do Mar Tyrannulet (Phylloscartes difficilis) as Least Concern. We welcome any comments to the proposed listing. Information is particularly requested on the population size and the likely rate of decline in population size or area of habitat.

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’s Red List status. Therefore, please make sure your comments are about the proposed listing. 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

Bird, J. P., Martin, R., Akçakaya, H. R., Gilroy, J., Burfield, I. J., Garnett, S. G., Symes, A., Taylor, J., Şekercioğlu, Ç. H. and Butchart, S. H. M. 2020. Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology online first view.

Global Forest Watch. 2020. Interactive Forest Change Mapping Tool. Available at: https://www.globalforestwatch.org/map/. (Accessed: 2020).

Parker, T.A., Stotz, D.F. and Fitzpatrick, J.W. 1996. Ecological and distributional databases. In: Stotz, D.F., Fitzpatrick, J.W., Parker, T.A. and Moskovits, D.K. (eds), Neotropical bird ecology and conservation, pp. 113-436. University of Chicago Press, Chicago.

Ridgely, R.S. and Tudor, G. 1994. The birds of South America. University of Texas Press, Austin, Texas.

Thiollay, J. M. 1986. Structure comparee du peuplement avien dans trois sites de foret primaire en Guyane. Revue d’Ecologie (La Terre et la Vie) 41: 59-105.

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.

WikiAves. 2018. Estalinho. Available at: http://www.wikiaves.com.br/wiki/estalinho. (Accessed: 23 March 2020).

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4 Responses to Archived 2020 topic: Serra do Mar Tyrannulet (Phylloscartes difficilis): revise global status?

  1. Hannah Wheatley (BirdLife) says:

    Global Forest Change data on tree cover loss up to 2019 have now been released and made available via Global Forest Watch. Based on these data, approximately 4% of tree cover was lost between 2009 and 2019 within the species’s range (Global Forest Watch 2020). This new information does not change the suspected population reduction over the past ten years.

    Over three years from 2017-2019, approximately 1.6% of tree cover within the species’s range was lost over three years (Global Forest Watch 2020). If this rate were to continue across ten years, this would equate to a loss of 5% of tree cover. Hence, over the next ten years, the population size is now suspected to undergo a reduction of 1-9%.

    This new information does not affect the proposed category change.

  2. 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

  3. 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 classification 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.

  4. Red List Team (BirdLife International) says:

    Recommended categorisation to be put forward to IUCN

    The final categorisation for this species has not changed. Serra do Mar Tyrannulet is recommended to be listed as Least Concern.

    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.

Comments are closed.