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Dwarf Jay Cyanolyca nanus



Justification

Justification of Red List Category
This species has a small population, which is in decline due to habitat loss within its restricted range. The subpopulation structure has not been assessed, but it is believed that the species forms several relatively small subpopulations. It is therefore assessed as Near Threatened.

Population justification
In Hidalgo the population density has been estimated at 4.4 individuals per km2 (M. Martínez-Morales in litt. 2016). Assuming that this density is representative and that only a proportion of its range is occupied, this would equate to a population of c.4,100 individuals; roughly equating to 2,750 mature individuals, here placed in the band 2,500-9,999 mature individuals. Where suitable habitat persists, the species may be locally common. Given the fragmentation of the range, it is assumed that the species forms several small subpopulations.

Trend justification
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. The Dwarf Jay depends on montane forest (Dinerstein et al. 1995, Ponce-Reyes et al. 2012). Therefore, it is conceivable that the rate of population decline is not equivalent, but slightly faster than the rate of deforestation. Nevertheless, it is unlikely that the rate of population decline exceeds 10% over three generations.

Distribution and population

The Dwarf Jay occurs in south-eastern Mexico. It is found from central Veracruz to Puebla and northern Oaxaca (Sierras Juárez, Aloapaneca and Zempoaltepec, La Chinantla), in eastern Querétaro (Tangojó) and in northeastern Hidalgo. It was feared extinct throughout this range except for the Cerro San Felipe in the Sierra Aloapaneca, where it remains quite common (A. G. Navarro in litt. 1998, Rojas-Soto et al. 2001, Martínez-Morales 2004).

Ecology

The species inhabits humid montane forest, where it is most abundant in pine-oak-fir forests with laurel and epiphytes  (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. Suitable breeding habitat has a sufficiently open canopy to allow the development of a dense subcanopy. The species forages mostly from the lower subcanopy to the higher shrub layer, where it gleans invertebrates from and around epiphytes. It occurs at elevations of 1,400-3,200 m (Rojas-Soto et al. 2001), but only above 1,670 m in the centre and south of its range. This is potentially a natural altitudinal distribution, but it may have been extirpated from the lower elevations in the south of its range. At Cerro San Felipe, the breeding season begins in early April.


Threats

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). The Dwarf Jay is prone to nest-desertion following human disturbance. Climate change is also expected to be an additional factor that impacts habitat loss (Ponce-Reyes et al. 2012). In the southern part of the range, the 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.

Conservation actions

Conservation Actions Underway

There are two protected areas within the species's range: the Sierra Gorda Biosphere Reserve and Benito Juárez National Park. Cerro San Felipe lies within the Benito Juárez National Park, but the boundaries of this relatively small reserve have never been demarcated (Salas et al. 1994), and thus it offers the species little protection (A. T. Peterson in litt. 1998). Eight voluntarily designated areas for conservation have been created in north Oaxaca: San Juan Teponaxtla Communal Ecological Reserve Zone, San Antonio del Barrio Conservation Area, San Pedro Tlatepusco Conservation Area, San Felipe de León Conservation Area, Tierra del Faisán Conservation Area, Nopalera del Rosario Conservation Area, Santo Domingo Cacalotepec Communal Conservation Zone, and La Cruz-Corral de Piedra (M. Martínez-Morales in litt. 2016).

Conservation Actions Proposed

Survey to assess more precisely the extent of its distribution. Demarcate and effectively protect the boundaries of Benito Juárez National Park. Protect sites where the species has been recently recorded.

Identification

20-23 cm. Small, slender and agile, blue jay. Slate-blue except for black mask bordered by slight, whitish supercilium and whitish throat highlighted by diffuse breast-band. Voice Repeated two-syllable, high-pitched nasal yeeyip yeeyip. Occasionally also longer, harsh squawk. Hints Often accompanies mixed-species flocks with Grey-barred Wren Campylorhynchus megalopterus.

Acknowledgements

Text account compilers
Westrip, J., Mahood, S., Hermes, C., Harding, M., Pople, R., Sharpe, C.J., Capper, D., Isherwood, I.

Contributors
Escalante, P., Martínez-Morales, M., Navarro, A.G. & Peterson, A.T.


Recommended citation
BirdLife International (2021) Species factsheet: Cyanolyca nanus. Downloaded from http://www.birdlife.org on 24/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 24/10/2021.