Justification of Red List Category
This species is listed as Vulnerable owing to its small population, which is thought to be declining.
Surveys carried out in broadleaf forest in Guatemala found a density of 33-93 individuals per km2; based on this density the population in Guatemala was estimated to number 8,250-23,250 individuals (Eisermann et al. 2011a). However, the densities used in this calculation were estimated from surveys at 1,400-1,900 m, where the species is more abundant than at 900-1,300 m, and the density estimates may have been affected by the patchy nature of forest in the survey areas (see Eisermann et al. 2011a). The relative abundance in Mexico was found to be lower; surveys at El Triunfo Biosphere Reserve recorded only 0.84 individuals per km2 (Secretaría de Medio Ambiente, Vivienda e Historia Natural 2011, Enríquez et al. 2013, P. Enríquez in litt. 2019). Assuming that the population in Guatemala is much larger than the population in Mexico, the global population is tentatively placed in the band of c.10,000-25,000 individuals. This roughly equates to 6,000-17,000 mature individuals. The map of sightings of this species on eBird (eBird 2019) suggests that the species occurs in either one or two subpopulations. If it were to be considered as two subpopulations, then the largest subpopulation would probably contain significantly greater than 1,000 mature individuals. Unless new information becomes available, the species is precautionarily assumed to occur in only one subpopulation.
The species is thought to be in moderate decline owing to habitat loss, primarily for coffee cultivation. The population trend for this species has not been directly estimated. The rate of habitat loss within the range is placed in the band 10-15% over ten years (K. Eisermann in litt. 2019). The species is precautionarily inferred to undergo a slow population decline.
Tangara cabanisi occurs in the Sierra Madre de Chiapas of southern Mexico and south-western Guatemala (Heath and Long 1991, Collar et al. 1992, Eisermann et al. 2011a). The only recent records in Mexico are from El Triunfo and Tacaná Biosphere Reserve (P. Enríqez in litt. 2019). In Guatemala, it has been recorded on the southern slope of the Santa María volcano, at Dos Marías Reserve, on the Sierra Madre south of San Marcos, Tajumulco volcano, Atitlán volcano, in middle valley of Madre Vieja River north of Pochuta, Santo Tomás volcano, Lacandón volcano, in the valley of the Nicán river, Chicabal volcano and Agua volcano (Cooper 2003, Eisermann et al. 2011a, Eisermann and Avendaño 2018). Despite this restricted distribution, it is apparently locally common in these areas (M. Thompson in litt. 1998, Cooper 2003, Eisermann et al. 2011a, Eisermann and Avendaño 2018).
The species inhabits humid broadleaf evergreen forest at 1,000-1,700 m in Mexico, with most sightings between 1,250 m and 1,650 m, but it has been recorded from 860 m up to 1,900 m in Guatemala (J. F. Hernandez in litt. 1998, Eisermann et al. 2011a,b), where it appears to be most abundant above 1,400 m (Eisermann et al. 2011a). Apart from broadleaf forests, the species has also been recorded in degraded and edge habitats, including coffee plantations adjacent to primary forest, where it has also been observed nesting (K. Eisermann in litt. 2007, Eisermann et al. 2011a,b, P. Enríquez in litt. 2019). Nevertheless, a comparison of encounter rates in primary broadleaf forest and coffee plantations indicates that the species is more abundant in primary forest (Eisermann et al. 2011a). Despite on occasions being more visible in edge environments, it mostly forages in the upper strata and canopy of pristine forest, and may undertake local movements in response to the maturing syconia of Ficus trees (J. F. Hernandez in litt. 1998). It feeds mainly on fruits and invertebrates (Eisermann 2011). The species breeds in the wet season, from April to September (Eisermann et al. 2011b). It was previously reported to have a distinct nesting preference for Ficus cookii (Gómez de Silva 1997); however, nests have now been located in at least 23 different tree species, including a conifer (Neocupressus lusitanica), cypress trees Cupressus sp.(3) and an Inga sp. used as shade trees in a coffee plantation, as well as non-native species (K. Eisermann in litt. 2007, Eisermann 2011, Eisermann et al. 2011b). Limited observations suggest that the incubation period lasts c.14 days, followed by a brooding period of c.17 days (Eisermann et al. 2011b). It is highly social, and flocks of up to 26 birds have been recorded (T. Gullick per M. Thompson in litt. 1998).
The main threat to the species is the fragmentation and loss of its forest habitat (P. Enríquez in litt. 2019). Its altitudinal range coincides with the optimal land for coffee cultivation. More than one-third of Mexico's coffee is grown in Chiapas, and production has been centred on the Pacific slope of the Sierra Madre since the beginning of the 20th century. Although the species has been recorded in coffee plantations, it appears to be absent from the interior of intensive coffee plantations (Eisermann et al. 2011a). Agricultural land is expanding because new settlements in the mountains are legally leasing unprotected, national territory land. About 45% of the suitable habitat that remains in its potential range in Guatemala is unprotected (Eisermann et al. 2011a). Pressure on the species's habitat is expected to increase because of a rapidly growing human population (e.g. a 35% increase from 1994 to 2002) (K. Eisermann in litt. 2007). A further potential threat is habitat damage due to storms and hurricanes (P. Enríquez in litt. 2019). In Mexico, the frequency of forest fires is increasing during the dry season; in 2019 over 220 ha were lost in the El Triunfo Biosphere Reserve (Triunfo Reserve Manager per P. Enríquez in litt. 2019). Furthermore, mining concessions placed in the southern part of the El Triunfo Biosphere Reserve may potentially lead to opencast mining within or in the direct vicinity to the reserve (P. Enríquez in litt. 2019, Godínez-Gómez and Mendoza 2019).
Conservation Actions Underway
In Mexico, the species occurs in El Triunfo Biosphere Reserve, but mostly in the buffer zone which is occupied by several small but expanding communities. The Secretary of Environment and Natural History of Chiapas has been carrying out a monitoring programme for several years (P. Enríquez in litt. 2019). Of the sites where it has been recorded recently in Guatemala, at least seven have legal protection status, including several private nature reserves. These reserves include coffee plantations and primary forest. By offering tourism services (including birdwatching), some of these reserves put a value to primary habitats, which benefits the local population economically (K. Eisermann in litt. 2007, Eisermann 2011). The species is listed as Threatened by Extinction at the national level in Mexico (SEMARNAT 2010).
15 cm. Predominantly sky-blue tanager. Purplish-azure crown. Black lores and iris form masked appearance. Mottled green mantle. Pale sky-blue rump and uppertail. Black central tail feathers edged blue. Paler underparts scaled black on upper breast. Black scapulars, and greater and median wing-coverts (narrowly edged blue on greaters). Azure outer webs of remiges, black inner webs of flight feathers. Voice Twittering and high sii calls. High wi sseeu song.
Text account compilers
Capper, D., Sharpe, C.J., Isherwood, I., Hermes, C., Mahood, S.
Eisermann, K., Enríquez, P., Gullick, T., Hernandez, J.F., Thompson, M., Pople, R. & Taylor, J.
BirdLife International (2021) Species factsheet: Tangara cabanisi. Downloaded from http://www.birdlife.org on 27/01/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 27/01/2021.