Justification of Red List Category
This species is listed as Endangered owing to its very small, fragmented and declining range, in which suitable habitat continues to be significantly reduced through conversion to coffee cultivation.
The population is estimated to number 2,500-9,999 individuals based on an assessment of known records, descriptions of abundance and range size. This is consistent with recorded population density estimates for congeners or close relatives with a similar body size, and the fact that only a proportion of the estimated Extent of Occurrence is likely to be occupied. This estimate is equivalent to 1,667-6,666 mature individuals, rounded here to 1,500-7,000 mature individuals.
There are no new data on population trends, but the species is suspected to be in moderate decline owing to habitat loss, primarily for coffee cultivation.
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 Biosphere Reserve. 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 and Chicabal volcano (Cooper 2003, Eisermann and Avendaño 2007a, Eisermann et al. 2011a). Despite this restricted distribution, it is apparently locally common in these areas (M. Thompson in litt. 1998, Cooper 2003, Eisermann et al. 2011a). Surveys carried out in Guatemala in 2008, employing distance sampling methodology, found an average density of 56 individuals per km2 (95% CI: 33-93 per km2) which, based on an estimate of 250 km2 of broadleaf forest within the species's potential range at 900-1,900 m elevation, suggests that the population in Guatemala numbers 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). With this in mind, the total population estimate has been revised upwards but is conservatively estimated to include fewer than 20,000 mature individuals.
It 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). It appears, however, to be most abundant above 1,400 m in Guatemala (Eisermann et al. 2011a). It has 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), although 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).
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).
Conservation Actions Underway
It occurs in El Triunfo Biosphere Reserve, but mostly in the buffer zone which is occupied by several small but expanding communities. 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).
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., Isherwood, I., Mahood, S., Pople, R., Sharpe, C J, Taylor, J.
Hernandez, J., Thompson, M., Gullick, T., Eisermann, K.
BirdLife International (2018) Species factsheet: Tangara cabanisi. Downloaded from http://www.birdlife.org on 19/09/2018. Recommended citation for factsheets for more than one species: BirdLife International (2018) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 19/09/2018.