Archived 2019 topic: Dwarf Jay (Cyanolyca nanus): revise global status?

BirdLife species factsheet for Dwarf Jay

Dwarf Jay (Cyanolyca nanus) occurs in south-eastern Mexico. It is found from central Veracruz to Puebla and the Sierras Juárez, Aloapaneca and Zempoaltepec in northern Oaxaca, in eastern Querétaro and in northeastern Hidalgo, where it may be locally common where suitable habitat persists (A. G. Navarro in litt. 1998, Rojas-Soto et al. 2001, Martínez-Morales 2004). The population is estimated to number 2,750 mature individuals (BirdLife International 2019).

The species inhabits humid montane forest, where it is most abundant in pine-oak-fir forests with laurel and epiphytes between 1,400 and 3,200 m (Rojas-Soto et al. 2001). In oak-dominated forests, it reaches lower densities. Dwarf Jay is also common in secondary forests, depending on the predominance of the preferred trees and nearby tracts of primary forest.

Logging, agricultural expansion, firewood-gathering, road and tourist developments, sheep-ranching, intense grazing and intensive urbanisation have resulted in extensive and continuing destruction and fragmentation of the species’s habitat (Dinerstein et al. 1995). Dwarf Jay is prone to nest-desertion following human disturbance. Climate change is also expected to be an additional factor of habitat loss (Ponce-Reyes et al. 2012). In the southern part of the range, Dwarf Jay only occurs above 1,670 m; this is possibly a natural altitudinal distribution, but the species may have been extirpated from the lower elevations in this part of the range.

Dwarf Jay is currently listed as Vulnerable under Criteria A2c+3c+4c (BirdLife International 2019), indicating a rapid decline in area, extent and/or quality of habitat. However, incorporating new information on the rate of forest loss and on the population structure, this species appears to warrant a change in Red List status. Therefore, we present here our reassessment against all criteria for the species.

Criterion A – The population of Dwarf Jay it thought to be in decline, but the rate of decline has not been estimated directly. Tracewski et al. (2016) measured the forest loss within the species’s range between 2000 and 2012 as c. 41 km2. This roughly equates to a rate of forest loss of 2.4% over three generations (20.1 years) for this species. Dwarf Jay depends on montane forest; the only threats known for this species include forest clearance, anthropogenic disturbance and climate change effects (Dinerstein et al. 1995, Ponce-Reyes et al. 2012). Therefore, while we can assume that the species is declining in response to forest loss, it is conceivable that the rate of population decline is not equivalent, but slightly faster than the rate of deforestation. However, it is unlikely that the rate of population decline approaches the threshold for Vulnerable under this criterion (≥ 30% over three generations). Therefore, Dwarf Jay may be listed as Least Concern under Criterion A.

Criterion B – The Extent of Occurrence (EOO) for this species is 44,800 km2. This does not meet the threshold for Vulnerable (EOO < 20,000 km2). Therefore, Dwarf Jay may be listed as Least Concern under Criterion B1. The Area of Occupancy (AOO) has not been calculated and Dwarf Jay cannot be assessed against Criterion B2.

Criterion C – The global population size is estimated at 2,750 mature individuals. This meets the threshold for Vulnerable under this criterion (< 10,000 mature individuals). However, in order to be listed under Criterion C, other conditions have to be met.

The rate of decline in the species has not been directly estimated, and so Criterion C1 cannot be used. Instead, the population decline can be inferred from habitat loss (Tracewski et al. 2016), and it thus depends on the species’s subpopulation structure whether it qualifies for listing as Vulnerable under condition 2a. Given the fragmentation of the range, we can assume that the species forms several subpopulations, and thus Criterion C2a(ii) does not apply. However, the global population size is very small. Therefore, while the largest subpopulation might not meet the threshold for Vulnerable under Criterion C2a(i) (≤ 1,000 mature individuals), it is likely that the size of the largest subpopulation approaches this threshold. The species is not known to undergo extreme fluctuations, so it does not trigger the conditions for Criterion C2b. Thus, Dwarf Jay may be tentatively listed as Near Threatened under Criterion C2a(i).

Criterion D – The global population size is estimated at 2,750 mature individuals. This is too large to meet the threshold for Vulnerable (< 1,000 mature individuals). Therefore, Dwarf Jay may be listed as Least Concern under Criterion D.

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 Dwarf Jay (Cyanolyca nanus) be listed as Near Threatened under C2a(i). We welcome any comments on this 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 its Red List status. Therefore, please make sure your comments are relevant to the discussion outlined in the topic.

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

BirdLife International. 2019. Species factsheet: Cyanolyca nanus. http://www.birdlife.org (Accessed 14 February 2019).

Dinerstein, E.; Olson, D. M.; Graham, D. J.; Webster, A. L.; Primm, S. A.; Bookbinder, M. P.; Ledec, G. 1995. A conservation assesssment of the terrestrial ecoregions of Latin America and the Caribbean. World Bank, Washington, D.C., U.S.A.

Martínez-Morales, M. A. 2004. Nuevos registros de aves en el bosque mesófilo de montaña del noreste de Hidalgo, México. Huitzil 5: 12-19.

Ponce-Reyes, R.; Reynoso-Rosales, V.-H.; Watson, J. E. M.; VanDerWal, J.; Fuller, R. A.; Pressey, R. L.; Possingham, H. P. 2012. Vulnerability of cloud forest reserves in Mexico to climate change. Nature Climate Change 2: 448-452.

Rojas-Soto, O. R.; Sahagún-Sánchez, F. J.; Navarro, S. A. G. 2001. Additional information on the avifauna of Querétaro, Mexico. Cotinga 15: 48-52.

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.

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1 Response to Archived 2019 topic: Dwarf Jay (Cyanolyca nanus): revise global status?

  1. 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.

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