BirdLife species factsheet for Maranon Antshrike
Maranon Antshrike (Thamnophilus shumbae) is endemic to Peru, where it occurs in a small area in the drainage of Río Marañón. The species is not well known. It inhabits deciduous forest woodland, but also lowland arid scrub and riparian thickets at elevations below 1,000 m (del Hoyo et al. 2020). The species is thought to be of low sensitivity and to tolerate habitat conversion and degradation (del Hoyo et al. 2020).
The species is described as fairly common, but the population size has not been quantified directly (del Hoyo et al. 2020). Based on the recorded population densities of congeners (Thamnephilus aethiops: 2 mature individuals/km2 and T. schistaceus: 20 mature individuals/km2 in Peru [Santini et al. 2018]) and the area of the species’s mapped range (3,000 km2), and assuming that about 10% of the range is occupied, the population is estimated to fall in the band 600-6,000 mature individuals.
Maranon Antshrike has been considered Data Deficient due to the lack of data on population size and trend (BirdLife International 2020). However, new information has become available, allowing the species’s Red List category to be assessed. Therefore, we have fully reviewed the species here against all criteria.
Criterion A – The only threat that is possibly affecting Maranon Antshrike is the loss and degradation of its habitat. Tree cover within the range has been lost at a rate of up to 7% over the past three generations (10.8 years*; Tracewski et al. 2016, Global Forest Watch 2020). The species is not dependent on forest cover, but also occurs in scrubland and thickets, and seems to be able to tolerate a certain level of habitat degradation (del Hoyo et al. 2020). Therefore, while the species may tentatively be suspected to undergo a decline, the rate of decline is unlikely to exceed 10% over three generations. Maranon Antshrike is therefore listed as Least Concern under Criterion A.
Criterion B – The Extent of Occurrence (EOO) for this species is 3,400 km2. The maximum Area of Occupancy (AOO), as calculated by a 4 km2 grid over the area of mapped range, is 3,388 km2. Thus, the species meets the threshold for Endangered under Criterion B1 (EOO < 5,000 km2). To be listed as threatened under this criterion however, the species requires at least two further conditions to be met..
The species is thought to form just one subpopulation and can thus not be considered severely fragmented (see IUCN Standards and Petitions Committee 2019). Habitat loss and degradation appears not to severely affect the species; therefore the number of locations** of occurrence is likely considerably larger than 10. Maranon Antshrike thus does not meet sub-criterion a. From the moderate rate of forest loss, we can infer that habitat quality is in a slow continuing decline, and sub-criterion b(iii) is met. The species is not known to undergo extreme fluctuations, and thus sub-criterion c is not met. Overall, even though the EOO is very small, Maranon Antshrike does not meet sufficient sub-criteria. It therefore qualifies as Near Threatened, approaching the threshold for listing as threatened under Criterion B1b(iii).
Criterion C – The population size is estimated at 600-6,000 mature individuals. Assuming that the population size is closer to the lower end of the estimate, this meets the threshold for listing as threatened under Criterion C. However, in order to do so, the species must meet further sub-criteria.
All individuals are thought to form just one subpopulation. Despite its apparent tolerance of converted habitats, the species is suspected to be in slow decline as the quality of its habitat is decreasing. A suspected decline, however, precludes a listing as threatened, and as such Maranon Antshrike may be considered Near Threatened, approaching the threshold for listing as threatened under Criterion C2a(ii).
Criterion D – The population is preliminarily placed in the band 600-6,000 mature individuals. Assuming that the true population size is closer to the lower end of the estimate, the species qualifies for listing as Vulnerable under Criterion D1.
Criterion E – To the best of our knowledge, there has been no quantitative analysis of extinction risk conducted for this species. Therefore, it cannot be assessed against this criterion.
Therefore, it is suggested that Maranon Antshrike (Thamnophilus shumbae) be listed as Vulnerable under Criterion D1. 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).
**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 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: Thamnophilus shumbae. http://www.birdlife.org (Accessed 2 April 2020).
del Hoyo, J.; Collar, N.; Kirwan, G. M. 2020. Maranon Antshrike (Thamnophilus shumbae). 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, Spain. https://www.hbw.com/node/1343590 (Accessed 2 April 2020).
Global Forest Watch. 2020. Interactive Forest Change Mapping Tool. http://www.globalforestwatch.org/ (Accessed 2 April 2020).
IUCN. 2001. IUCN Red List Categories and Criteria: Version 3.1. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K.
IUCN. 2012. IUCN Red List Categories and Criteria: Version 3.1. Second edition. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K. www.iucnredlist.org/technical-documents/categories-and-criteria.
IUCN Standards and Petitions Committee. 2019. Guidelines for using the IUCN Red List Categoreis and Criteria. Version 14. http://www.iucnredlist.org/documents/RedListGuidelines.pdf.
Santini, L.; Isaac, N. J. B.; Ficetola, G. F. 2018. TetraDENSITY: A database of population density estimates in terrestrial vertebrates. Global Ecology and Biogeography 27: 787-791.
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.