BirdLife species factsheet for Cipo Canastero
This discussion was first published as part of the 2019 Red List update. At the time a decision regarding the status of this species was pended and the post remained open. Following experts’ review of the species factsheet, the topic has now been updated to reflect the most recent information. The initial topic can be found here.
Cipo Canastero (Asthenes luizae) occurs in the central-southern Espinhaço Range, Minas Gerais, Brazil. It was discovered in 1985 in a small area within the Serra do Cipó (Pearman 1990, Vielliard 1990). Subsequent surveys detected the species in several other ridges within the central Espinhaço Range (Chaves Cordeiro et al. 1998, Vasconcelos et al. 2002, Vasconcelos and D’Angelo Neto 2007, Vasconcelos 2009, Chaves 2014).
Cipo Canastero is restricted to campo rupestre: isolated rocky outcrops with dry, bushy vegetation. It ranges from 1,100 to 2,000 m (Freitas et al. 2019) and prefers steep, well vegetated slopes. Currently, the most important threat to the species is thought to be brood parasitism by the recently introduced Shiny Cowbird (Molothrus bonariensis) (Costa 2015). Other threats include fires caused by tourist campfires or from escaped agricultural fires (L. E. Lopes in litt. 2009, Vasconceles 2009, Costa 2015), grazing, incursion of invasive grasses (Freitas et al. 2019), development for tourism and infrastructure, mineral extraction and climate change. A model of the impact of climate on the potential range of rupestrian grasslands in the Espinhaço Range predicted that around half of these grasslands would be lost by 2080 (Bitencourt et al. 2016). Other models indicated that rupestrian grasslands might lose up to 95% of their current suitable area by the end of the century (Wilson Fernandes et al. 2014).
Currently, Cipo Canastero is listed as Near Threatened, approaching the threshold for listing as threatened under Criterion B1ab(iii) (BirdLife International 2020). 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. After re-calculating the EOO for Cipo Canastero, the species appears to warrant a change in Red List status. Therefore, we present here our reassessment against all criteria for the species:
Criterion A – Studies of ringed individuals and territories in Serra do Cipó over six years by Costa (2015) indicated a declining population trend from 2009 to 2015. Therefore, there is an inferred continuing decline in the number of mature individuals. The species’s generation length is estimated to be 2.89 years (Bird et al. 2020)*; since three generations would be less than ten years for this species, reductions under Criterion A should be assessed over a period of ten years. There is no quantified estimate of the rate of reduction over the past ten years, or ten years into the future, so the species cannot be assessed under Criterion A.
Criterion B – The newly calculated Extent of Occurrence (EOO) for this species, based on an updated range map (not yet available on the BirdLife Data Zone), is 37,000 km2. This does not meet or approach the threshold for Vulnerable (EOO < 20,000 km2). Therefore, Cipo Canstero is assessed as Least Concern under Criterion B1.
Based on the total area of 4 km2 squares intersecting the species’s occurrence records, the minimum Area of Occupancy (AOO) was estimated to be 228 km2 (Freitas et al. 2019). However, the species is unlikely to be confined only to the 4 km2 squares in which it has been recorded, so this likely represents an underestimate.
Based on the total area of 4 km2 squares intersecting the species’s mapped range, the maximum AOO is inferred to be 17,100 km2. However, the species has specialist habitat requirements and is unlikely to occur everywhere in the mapped range, so this figure likely represents an overestimate.
The best estimate of the AOO is inferred to be 6,000 km2, based on the total area of 4 km2 squares intersecting the area of a species distribution model (Freitas et al. 2019), with areas without records removed.
This range of estimates of AOO could qualify the species for Endangered or Least Concern under Criterion B2. The best estimate does not meet or approach the threshold for listing the species as threatened under Criterion B2 and would qualify the species for listing as Least Concern under Criterion B2. If there is considerable uncertainty around whether the true AOO falls beneath the threshold for listing the species as threatened under this criterion, the species could qualify for Near Threatened. To list the species as threatened or Near Threatened under Criterion B, at least two further conditions have to be met.
The species is not severely fragmented, since >50% of its total area of occupancy is not in habitat patches that are either smaller than would be required to support a viable population, or separated from other habitat patches by a large distance. According to the IUCN Red List Categories and Criteria, ‘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’ (IUCN 2012). The main threat to the species is considered to be brood parasitism by the recently introduced Shiny Cowbird (Molothrus bonariensis) (Costa 2015). Although this threat is thought to be causing population declines across the species’s range, the number of locations would likely be greater than ten. Another threat is the risk of fires caused by tourist campfires, or from escaped agricultural fires (L. E. Lopes in litt. 2009, Vasconceles 2009, Costa 2015). The species occurs on nine ‘sky islands’, but it is likely that it would take more than one fire to destroy all habitat at some of these (particularly the Diamantina Plateau), so the number of locations based on the threat of fire would be greater than ten. A model of the impact of climate change on the potential range of rupestrian grassland in the Espinhaço Range predicted that around half would be lost by 2080 (Bitencourt et al. 2016). Other models indicated that rupestrian grasslands might lose up to 95% of their current suitable area by the end of the century (Wilson Fernandes et al. 2014). Although climate change is projected to impact the majority of the species’s range, this is uncertain and is predicted to happen over a period of decades, so is unlikely to rapidly (i.e. within one generation) affect all individuals over a large area. Therefore, we consider that the number of locations is likely to be greater than ten, but based on the threat of brood parasitism by Shiny Cowbird, it may be approaching ten.
Studies of ringed individuals and territories in Serra do Cipó over six years by Costa (2015) indicated a declining population trend from 2009 to 2015. Therefore, there is an inferred continuing decline in the number of mature individuals. A continuing decline in the area and quality of habitat, EOO, AOO and number of locations may also be projected from models of the impact of climate change on rupestre grassland (Wilson Fernandes et al. 2014, Bitencourt et al. 2016). Condition b is met.
There is no evidence that the species’s population or range size are undergoing extreme fluctuations. Condition c is not met.
Although the species’s minimum estimate of AOO would qualify the species for listing as Endangered, the best estimate of AOO does not meet or approach the threshold for Vulnerable. Although condition b is met, condition c is not and we do not have evidence to suggest that condition a is met. Depending on whether the number of locations is thought to be close to ten, Cipo Canastero may be assessed as Near Threatened, approaching the threshold for listing as threatened under Criterion B2ab(i,ii,iii,iv,v), or as Least Concern.
Criterion C – Surveys in 2009-2010 in Serra do Cipó found a mean population density of 29 individuals per km2 in campo rupestre habitat, and 13 individuals and five breeding pairs per km2 across the study area (Freitas 2011). Another analysis of surveys at Serra do Cipó provided mean population densities of 35.2 adult individuals per km2 in campo rupestre habitat, and 13.6 adults per km2 across the study area (Freitas et al. 2019). Considering paired individuals only, this study found an average of 22.9 per km2 in campo rupestre habitat, and 8.7 per km2 across the study area (Freitas et al. 2019). Surveys from 2009-2015 in Serra do Cipó found an average density of 17 adult individuals per km2 of rocky outcrops, and 8 adults per km2 of study area, with a lower density of paired individuals (7 and 3 respectively) due to the sex ratio bias (Costa 2015).
Based on the area of habitat within the Cipo Canastero’s range, the global population size was projected to be around 21,800 (7,400 – 47,600) paired individuals (Costa 2015). The species has a strongly male-biased sex ratio (Freitas 2011, Costa 2015), with an adult population composed of c.70% males (Costa 2015, Freitas et al. 2019). Accordingly, the population size estimate was based on the number of paired individuals (Costa 2015). This range of estimates could qualify the species as Vulnerable, Near Threatened or Least Concern under Criterion C. The best estimate, 21,800 mature individuals, would qualify the species for Least Concern under Criterion C.
To list the species as threatened or Near Threatened under Criterion C, further conditions must also be met. Studies of ringed individuals and territories in Serra do Cipó over six years by Costa (2015) indicated a declining population trend from 2009 to 2015. Therefore, there is an inferred continuing decline in the number of mature individuals. We do not have data from which to estimate the rate of decline, so the species cannot be assessed under Criterion C1.
The distribution range is divided into three areas separated by some distance and there are at least three subpopulations. Costa (2015) estimated 700 mature individuals in the northern part of the range, 1,900 in the central part and 19,800 in the southern part. However, it is likely that there are further subpopulation divisions within these blocks, particularly the southern block, due to narrower gaps of around 10 km between areas of suitable elevation. The species is thought to have a low dispersal distance (Costa 2015). A study of the species’s habitat and elevational range identified nine ‘sky islands’ within the range, which may represent separate subpopulations (Freitas et al. 2019). The largest of these is the Diamantina Plateau, which was estimated to represent 55% of the total range (Freitas et al. 2019). Based on the population estimates described above, and assuming that the Diamantina Plateau supports around 55% of the total population, there are likely to be at least 4,000 mature individuals in the largest subpopulation. Neither condition C2a(i) nor condition C2a(ii) is met. There is no evidence that the species’s population size is undergoing extreme fluctuations so the species doesn’t meet condition C2(b).
Although the minimum inferred population size falls beneath the threshold for listing Cipo Canastero as Vulnerable under Criterion C and there is a continuing decline in population size, the best estimate of the population size does not meet or approach the threshold for listing the species as Vulnerable. Furthermore, there is no data from which to estimate or infer a rate of decline, and none of conditions C2a(i), C2a(ii) or C2b are met. The species therefore qualifies as Least Concern under Criterion C.
Criterion D – The population size is too large to approach the threshold for Vulnerable (1,000 mature individuals). Therefore, Cipo Canastero is assessed as Least Concern under Criterion D.
Criterion E – A Population Viability Analysis (PVA) has been carried out using the software VORTEX, and based on data gained through surveys carried out in 2009-2015 in Serra do Cipó (Costa 2015). Twelve candidate models were constructed by varying three parameters (juvenile mortality, sex-specific mortality rates and the rate of reproductive success), and three models were selected from those that best fitted the population trends observed at Serra do Cipó in 2009-2015, representing optimistic, pessimistic and neutral scenarios. These models were then used to estimate the probability of extinction over 12, 20, 50 and 100 years for the global population. The probability of extinction in 12 years was estimated as 0% for the neutral and optimistic scenarios and 0.8 (± 0.4%) for the pessimistic scenario. The probability of extinction in 20 years was estimated as 0% for the optimistic scenario, 58.6% (± 2.2%) for the neutral scenario, and 95.6% (± 0.9%) for the pessimistic scenario. The probability of extinction in 100 years was estimated as 100% for all three scenarios. If accepted, these results would qualify the species for listing as Endangered under Criterion E.
The Red List Guidelines provide strict requirements and recommendations for the use of PVAs in Red List Assessments. In particular, it is noted that ‘when there is not sufficient data, or when the available information is too uncertain, it is risky to make a criterion E assessment with any method, including PVA’ (IUCN Standards and Petitions Committee 2019). In order to decide whether there is sufficient data, the Red List Guidelines recommend that model parameters are estimated, incorporating the uncertainties in the data, to provide ‘optimistic’ and ‘pessimistic’ estimates. These ranges of estimates may then be used to create a range of models to give a range of extinction risk estimates, and the range of these estimates used to determine whether the results are useful, and hence whether there is enough data (see IUCN Standards and Petitions Committee 2019, p. 74). The Red List Guidelines suggest that ‘all parameters be specified as ranges (or as distributions) that reflect uncertainties in the data (lack of knowledge or measurement errors)’ (see IUCN Standards and Petitions Committee 2019, p. 76).
Although a range of twelve candidate scenarios were created by Costa (2015), they did not incorporate the uncertainty of all parameters used, and they were only tested for the period of the population study (2009-2015), with an initial population size of 30 individuals. The optimistic and pessimistic scenarios used to assess extinction risk of the global population were selected out of those that best fitted trends seen at Serra do Cipó over 2009-2015, and did not incorporate the full range of uncertainty in the parameters. Indeed, in the documentation, it is explained that the full standard error in the percentage of breeding females was not included in the model, as it was too large. No range of estimates was included in the model for the initial global population size. The datasets from which the parameters were derived were small, including a study of breeding success based on 17 nests, and a demographic study based on 37 ringed (banded) individuals and monitoring of 22 territories (Costa 2015). The documentation acknowledges that some of the parameter estimates were uncertain due to the small number of individuals studied.
The Red List Guidelines further state that ‘the documentation should include a list of assumptions of the analysis, and provide explanations and justifications for these assumptions’ (see IUCN Standards and Petitions Committee 2019, p. 76). Whilst the documentation provided by Costa (2015) is extensive and explains most of the assumptions and judgements made in the derivation of the parameters, there is insufficient explanation of the initial global population size used in the model. The population size used was the estimated number of individuals in breeding pairs, as described under Criterion C above, and excluded both immature individuals and a proportion of adult males in the population. Although population size under Criteria C and D should be based on the number of mature individuals, this is not a requirement for PVAs used under Criterion E. It is not clear why the initial population size did not include all individuals, and since the model was not also run with all individuals included, we cannot tell how their inclusion would have affected the estimated extinction probabilities.
Lastly, the Red List Guidelines state that ‘all data files that were used in the analysis’ should be provided (see IUCN Standards and Petitions Committee 2019, p. 76). This is not the case here, although the parameter values used were specified.
We therefore consider that there is insufficient information presented for us to be able to determine whether there was enough data to provide useful results in the PVA, and the information that is presented suggests that there may not have been. The species cannot be assessed under Criterion E.
Based on the above assessment, it is proposed to list Cipo Canastero (Asthenes luizae) as Least Concern, or as Near Threatened, approaching the thresholds listing as threatened under Criterion B2ab(ii,iii,iv,v). The final category will depend on the determined AOO and number of locations. To allow us to achieve a clearer assessment of the status of Cipo Canastero, information is requested on the potential impact of threats of the species, and particularly the area (or proportion) of the range that is likely to be rapidly affected by threats.
Spatial files representing the species’s range (such as the Species Distribution Model) are also welcomed. GIS files should be emailed to firstname.lastname@example.org.
Please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of its Red List status. Therefore, please make sure your comments are relevant to the discussion outlined in the topic. 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.
Bird, J. P.; Martin, R.; Akçakaya, H. R.; Gilroy, J.; Burfield, I. J.; Garnett, S.; Symes, A.; Taylor, J.; Šekercioğlu, Ç.; Butchart, S. H. M. (2020). Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology online first view.
BirdLife International. 2020. Species factsheet: Asthenes luizae. http://www.birdlife.org.
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Pearman, M. 1990. Behaviour and vocalizations of an undescribed canastero Asthenes sp. from Brazil. Bulletin of the British Ornithologists’ Club 110: 145-153.
Vasconcelos, M. F. de; D’Angelo Neto, S. 2007. Padrões de distribuição e conservação da avifauna na região central da Cadeia do Espinhaço e áreas adjacentes, Minas Gerais, Brasil. Cotinga 28: 27-44.
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