Archived 2019 topic: White-winged Nightjar (Eleothreptus candicans): revise global status?

BirdLife species factsheet for White-winged Nightjar

White-winged Nightjar (Eleothreptus candicans) occurs in central South America, ranging from Bolivia to Brazil and Paraguay, from sea level to 210 m. The population of White-winged Nightjar is estimated to number 1,000-2,499 individuals based on an assessment of known records, descriptions of abundance and range size. This estimate is equivalent to roughly 600-1,700 mature individuals.

The species occupies open grasslands with scattered trees and bushes (Cleere et al. 2018), preferring dry savannas or open cerrado, often with termite mounds, anthills and palms Butia paraguayensis (Pople 2003, Cleere et al. 2018). It generally avoids areas of tall grass and woodland (Cleere et al. 2018). The species is apparently sedentary (Pople 2003), although there may be local movements in response to fires. The breeding season extends from September to January (Pople 2003).

The population of White-winged Nightjar is thought to be declining due to the destruction and degradation of its habitat. Two-thirds of the cerrado region had been heavily or moderately altered by 1993 (Conservation International 1999), with most of the destruction having occurred since 1950 (Cavalcanti 1999). The principal threats are grazing, invasive grasses, inappropriate fire regimes and conversion to agriculture for Eucalyptus plantations, pasture, soybeans and other exportable crops (Stotz et al. 1996, Parker and Willis 1997, Rodrigues et al. 1999, Pople 2003).

White-winged Nightjar species is known from only four small, disjunct locations*. It is found at one location* in northern Bolivia (Beni Biological Station in Beni [Davis and Flores 1994, Grim and Šumbera 2006]), at one location* in south-central Brazil (Emas National Park in Gioás [Rodrigues et al. 1999]), and two locations* in eastern Paraguay (Mbaracayú Forest Nature Reserve in Canindeyú and Laguna Blanca in San Pedro [Lowen et al. 1996, Clay et al. 1998, Pople 2003]). Additionally, there are historical records from Mato Grosso and São Paulo, Brazil, and from Paraguay (de Azara 1805). As the locations* of known occurrence are spread out over a large area, it is necessary to thoroughly assess the Extent of Occurrence (EOO) of this species, in order to allow an assessment against Criterion B.

IUCN define the EOO of a species as “the area contained within the shortest continuous imaginary boundary which can be drawn to encompass all the known, inferred or projected sites of present occurrence of a taxon, excluding cases of vagrancy” (IUCN 2001, 2012). The EOO effectively measures the spatial spread of areas currently known to be occupied by a species. This is important for species conservation as areas that are closer together are likely to experience more similar environmental conditions and processes. These processes include natural and anthropogenic threats to a species, and so areas closer together are more likely to suffer from the same threatening events. This could therefore lead to higher extinction risk for species that are spread over a small are compared to those spread over a larger area (see IUCN Standards and Petitions Subcommittee 2017).

It has been decided that the most appropriate way to calculate the EOO of a species is using Minimum Convex Polygons (IUCN 2001, 2012, Joppa et al. 2016). These are defined as “the smallest polygon in which no internal angle exceeds 180 degrees and which contains all the sites of occurrence” (IUCN 2001, 2012). For a species occurring in several discrete patches, this would still take the form of one continuous area, rather than separate polygons as such disjunctions are ‘strongly discouraged’ by IUCN (IUCN Petitions and Standards Subcommittee 2017). This is because using separate, discrete polygons would not accurately reflect how a large range size reduces the global impact on a species from local processes.

White-winged Nightjar is currently listed as Endangered under Criterion B1ab(iii,v). Since Minimum Convex Polygons have been adopted by IUCN as the method to calculate, we have re-calculated the EOO value for White-winged Nightjar using this methodology and present here out re-assessment against all criteria for the species.

The initial topic on this analysis can be found here.

Criterion A – The population of White-winged Nightjar is suspected to be in decline based on the large-scale destruction and degradation of cerrado habitat within the whole range and at known sites of occurrence. However, the likely rate of decline has not been estimated. Therefore, we do not have sufficient information to assess the species against Criterion A.

Criterion B – Using a Minimum Convex Polygon, the Extent of Occurrence of this species has been calculated as 627,000 km2. This is far too large for listing the species as Vulnerable under Criterion B1, and hence the species may be listed as Least Concern under this criterion. The Area of Occupancy has not been calculated; therefore, White-winged Nightjar cannot be assessed against Criterion B2.

Criterion C – The population of White-winged Nightjar is estimated to number 600-1,700 mature individuals. This may warrant listing White-winged Nightjar under Criterion C, as long as two other conditions are met. First, in order to qualify for listing as threatened under this criterion, the population decline must be observed, estimated, projected or inferred (IUCN 2001, 2012). The population of White-winged Nightjar is suspected to decline though, which is a lower level of confidence.  The species can therefore not be listed as threatened under Criterion C.

White-winged Nightjar fulfils a second condition however: For three of the four locations* of occurrence, the population size has been estimated. Mbaracayú Forest Nature Reserve (Paraguay) holds c. 40-150 individuals, equating to around 25-100 mature individuals (Pople 2003). Laguna Blanca (Paraguay) is suspected to hold at least 30 individuals, or at least 20 mature individuals (Grim and Šumbera 2006). In Bolivia, the sighting of an adult male in 2003 represents the first record at Beni since the initial male was collected in 1987 (Davis and Flores 1994, Grim and Šumbera 2006), suggesting that the population there may be small. The size of the population in Emas National Park (Brazil) is somewhat unclear, however. In the 1980s, the Emas population was assumed to number in the hundreds (if not larger), and density estimates from Mbaracayú suggest that, despite the paucity of recent records from Emas (Rodrigues et al. 1999), this may be an underestimate, as the National Park encompasses large areas of suitable habitat. Given the global population size of this species, it is highly likely that the population at Emas National Park consists of less than 1,000 mature individuals, and possibly even less than 250 mature individuals. Therefore overall, while the species does not meet enough conditions to be listed as threatened, it may be considered Near Threatened, approaching the threshold for listing as threatened under Criterion C2a(i).

Criterion D – The population size of this species is estimated at 600-1,700 mature individuals. Although the species may well be found to occur at other sites, it is currently known from just four disjunct locations*, with habitat loss being the most severe threat. Under the assumption that the true population size is close to the lower band of the estimate and thus falling below 1,000 mature individuals, the species may be listed as Vulnerable under Criteria D1+2.

Criterion E – To the best of our knowledge no quantitative analysis of extinction risk has been conducted for this species. Therefore, it cannot be assessed against this criterion.

Therefore, it is proposed that White-winged Nightjar (Eleothreptus candicans) be listed as Vulnerable under Criteria D1+2. We welcome any comments on this proposed listing and specifically request up-to-date information on the number and size of the subpopulations of White-winged Nightjar, in particular in Emas National Park.

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.

*Note that 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. The size of the location depends on the area covered by the threatening event and may include part of one or many subpopulations. 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.

References

Cavalcanti, R.B. 1999. Bird species richness and conservation in the Cerrado region of central Brazil. Studies in Avian Biology 19: 244-249.

Clay, R.P.; Capper, D.R.; Mazar Barnett, J.; Burfield, I.J.; Esquivel, E.Z.; Fariña, R.; Kennedy, C.P.; Perrens, M.; Pople, R.G. 1998. White-winged Nightjars Caprimulgus candicans and cerrado conservation: The key findings of project Aguará Ñu 1997. Cotinga: 52-56.

Cleere, N.; Kirwan, G.M.; de Juana, E. 2018. White-winged Nightjar (Eleothreptus candicans). 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/55198 (Accessed 12 September 2018).

Conservation International. 1999. Açoes prioritárias para a conservaçao da biodiversidade do Cerrado e Pantanal.

Davis, S.E.; Flores, E. 1994. First record of White-winged Nightjar Caprimulgus candicans for Bolivia. Bulletin of the British Ornithologists’ Club 114: 127-128.

de Azara, F. 1805. Apuntamientos para la historia natural de los páxaros del Paraguay y río de la Plata. Imprenta de la Viuda de Ibarra, Madrid.

Grim, T.; Šumbera, R. 2006. A new record of the endangered white-winged nightjar (Eleothreptus candicans) from Beni, Bolivia. Wilson Journal of Ornithology 118(1): 109-112.

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

Joppa, L.N.; Butchart, S.H.M.; Hoffmann, M.; Bachman, S.P.; Akçakaya, H.R.; Moat, J.F.; Böhm, M.; Holland, R.A.; Newton, A.; Polidoro, B.; Hughes, A. 2016. Impact of alternative metrics on estimates of extent of occurrence for extinction risk assessment. Conservation Biology 30: 362-370.

Lowen, J.C.; Bartrina, L.; Clay, R.P.; Tobias, J.A. 1996. Biological surveys and conservation priorities in eastern Paraguay (the final reports of Projects Canopy ’92 and Yacutinga ’95). CSB Conservation, Cambridge, U.K.

Parker, T. A.; Willis, E. O. 1997. Notes on three tiny grassland flycatchers, with comments on the disappearance of South American fire-diversified savannas. Ornithological Monographs 48: 549-555.

Pople, R. G. 2003. The Ecology and Conservation of the White-winged Nightjar Caprimulgus candicans (Eleothreptus candicans). PhD Thesis. University of Cambridge, Cambridge, U. K.

Rodrigues, F. H. G.; Hass, A.; Marini-Filho, O. J.; Guimarães, M. M.; Bagno, M. A. 1999. A new record of White-winged Nightjar Caprimulgus candicans in Emas National Park, Goiás, Brazil. Cotinga 11: 83-85.

Stotz, D.F.; Fitzpatrick, J.W.; Parker, T.A.; Moskovits, D.K. 1996. Neotropical Birds: Ecology and Conservation. University of Chicago Press, Chicago, U.S.A.

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3 Responses to Archived 2019 topic: White-winged Nightjar (Eleothreptus candicans): revise global status?

  1. Alexander Lees says:
  2. Red List Team (BirdLife International) says:

    Preliminary proposal
    Based on available information, our preliminary proposal for the 2019 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 2019 Red List categories will be published on the BirdLife and IUCN websites in December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  3. Red List Team (BirdLife International) says:

    Recommended categorisation to be put forward to IUCN
    Following further review, the recommended categorisation for this species has been changed.
    White-winged Nightjar is now recommended to be listed as Vulnerable under Criterion D1.
    The final 2019 Red List categories will be published on the BirdLife and IUCN websites in December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

Comments are closed.