Justification of Red List Category
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km² combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size may be moderately small to large, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The global population is thought to number 20,000-50,000 individuals (Curson 2020), which roughly equates to 13,000-33,000 mature individuals. In Guatemala, the species is common in oak-alder-conifer forest above the elevation of 2,300 m, but less common in cloud forests at the same elevation. In high-elevation (2,000-2,500 m) cloud forest on the Atlantic slope, a density of 0.25 individuals/ha was estimated. The total population in IBAs in Guatemala is assumed to be between 19,000 and 54,000 individuals (K. Eisermann unpubl. data). In Mexico, density estimates range from 0.12 to 3.7 individuals/km2 (Partida-Lara et al. 2020). Data quality is poor, and the total population is likely larger than estimated.
The population trend for this species has not been directly estimated, but the species is suspected to be in slow decline owing to habitat degradation. Forest cover within the range has been lost at a rate of 3% over the past ten years (Global Forest Watch 2020). The species prefers undisturbed forest, but appears to tolerate edges and degraded habitat. Therefore, while it may be possible to consider the species to be in decline, the rate of population decline is unlikely to exceed the rate of forest loss, and is here tentatively placed in the band 1-9% over ten years.
Cardellina versicolor is resident in the mountains of central and extreme south-east Chiapas, Mexico, and western Guatemala. Over the bulk of its range in Guatemala and on Volcán Tacaná in south-east Chiapas, it was historically very common and remains locally common (Wilson and Will 1997, Eisermann and Avendaño 2007). However, in central Chiapas, it was very rare in the mid-1980s, but became slightly more numerous at Cerro Huitepec and Rancho Nuevo from the late 1980s (Howell and Webb 1995).
It inhabits humid to semi-humid pine-oak-alder, pine, cypress and forest with undisturbed understorey, as well as high-elevation scrub and cloud forest. It is found at elevations of 1,800-3,500 m, but is most common above 2,800 m (Curson et al. 1994, Howell and Webb 1995, K. Eisermann in litt. 2012). It can tolerate forest edge and disturbed forest with a damaged understorey, but this is likely to be suboptimal habitat (Curson et al. 1994, Howell and Webb 1995, Partida-Lara et al. 2020).
The species is threatened by the loss and degradation of its habitat (Partida-Lara et al. 2020). Only 400 km2 of fragmented cloud-forest remnants remain in central Chiapas, many at altitudes unsuitable for this species (Bubb 1991, Wilson and Will 1997). In Guatemala, 900 km2 of cloud-forest remains, representing 3% of the original extent (Bubb 1991). Much of the remaining habitat in Chiapas has been altered by intense human use such as coppicing for charcoal production, timber extraction, farming, flower production, animal-grazing and subsistence wood-cutting (Wilson and Will 1997). In Guatemala, road construction is likely to lead to further human disturbance (J. F. Hernandez in litt. 1998). Human population in Guatemala increased by 35% between 1994 and 2002 and is estimated to double between 2010 and 2050 to a total of 28 million (INE 2002, CEPAL 2010). Most people live in the highlands with their favourable climate and fertile soils; human pressure on the habitat of this species is likely going to increase (K. Eisermann in litt. 2007). The dense human population, consisting mainly of small-scale farmers, causes extensive disturbance in the forest understorey (including in protected areas) by an extensive collection of firewood and collection of leaf litter as organic fertiliser. Feral dogs are probably negatively affecting the reproductive success of this ground-nesting warbler. About 50% of the range in Guatemala is located within areas used or planned for exploration and opencast mining (K. Eisermann in litt. 2012). The low population size in Chiapas in the mid-1980s may have been the result of the eruption of Volcán Chichonál in 1982, which carpeted large areas with volcanic ash (Howell and Webb 1995).
Conservation Actions Underway
Rancho Nuevo Ecological Protection Zone has been heavily grazed and recently taken over as a military training ground. Cerro Huitepec Biological Station is very small and surrounding forest is being rapidly cleared, leading to concerns that the reserve itself may not be large enough to support a viable population (Wilson and Will 1997). Protected areas cover 33% of Guatemala, including much of the range of this species, however this protection is ineffective (K. Eisermann in litt. 2007). It is on the watch list as part of the State of North America's Birds (North American Bird Conservation Initiative 2016).
13 cm. Red warbler with pink head. Whitish-pink head and neck with red forehead and dark lores. Dark red upperparts, darker on wings and tail. Bright pinkish-red underparts. Juvenile pinkish cinnamon-brown. Darker above with blackish wings, two pinkish wing-bars and blackish tail. Voice Song is series of chips and trills. High thin tsiu call.
Text account compilers
Capper, D., Eisermann, K., Hernandez, F., Isherwood, I., Khwaja, N., Pople, R., Schnell, J., Sharpe, C.J. & Westrip, J.R.S.
BirdLife International (2021) Species factsheet: Cardellina versicolor. Downloaded from http://www.birdlife.org on 21/01/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/01/2021.