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 species is described as 'fairly common' (Stotz et al. 1996). The population has not been quantified, but based on observational records it is suspected to number 10,000-19,999 mature individuals, though this requires confirmation.
Even though the subpopulation structure has not been assessed, it is here assumed that the species forms at least three moderately large subpopulations (per eBird 2021).
Population trends have not been directly estimated. Even though the species tolerates habitat disturbance, the population is suspected to be in slow decline locally due to habitat loss and degradation (Remsen 2020). The overall rate of decline is unlikely to exceed 10% over ten years.
Asthenes heterura occurs in central Cochabamba, La Paz, Potosí, Tarija and Chuquisaca, Bolivia, and in Jujuy, Salta, Tucumán and Catamarca, north Argentina (Ridgely and Tudor 1994; Fjeldså and Kessler 1996; Fjeldså and Mayer 1996; Remsen 2020). It has probably been overlooked (Ridgely and Tudor 1994; Fjeldså and Mayer 1996; T. Hjarsen in litt. 1999; S. Mayer in litt. 1999).
It is fairly common to uncommon in dense arid montane scrub and open Polylepis and Alnus woodland with grasses and mixed scrub (e.g. Gynoxys and Baccharis), at elevations of 3,000-4,200 m, locally down to 2,500 m (Vuilleumier 1969; Ridgely and Tudor 1994; Parker et al. 1996; Mazar Barnett et al. 1998; T. Hjarsen in litt. 1999; Remsen 2020). A specimen collected at 1,600 m in Bolivia in June 1914 suggests that it may descend in altitude during the winter months (M. Pearman in litt. 2001). It has also been found in tall clumps of Festuca bunchgrass, intermingled with areas of short turf and even patches of bare soil (Mazar Barnett et al. 1998), and shrubbery and hedgerows away from Polylepis (S. Mayer in litt. 1999).
Although not entirely dependent on Polylepis woodlands, their destruction through clearance for cultivation, firewood-collection and burning for pasture undoubtedly threatens some populations (Stattersfield et al. 1998). Pinus and Eucalyptus plantations are replacing suitable native vegetation within the range (T. Hjarsen in litt. 1999). The species nevertheless appears to tolerate at least moderate habitat degradation and is present on cattle pastures and on cultivated land (Remsen 2020).
Conservation Actions Underway
It occurs in Los Cardones National Park, Argentina
Conservation Actions Proposed
Quantify the population size. Monitor the population trend. Conduct ecological studies to determine the precise habitat requirements. Investigate its tolerance of habitat degradation and fragmentation. Grant protection to areas of suitable habitat to safeguard against clearance and degradation.
17 cm. A long tailed canastero of dry shrubbery. Upperparts greyish brown, underparts paler with a buffy tinge. Orangey chin patch which can look dark, with cinnamon borders. Rufous in wing forming a broad bar visible in flight. Narrow and inconspicuous eyebrow and loral buffy-cream. Tail brownish rufous with dull brown central rectrices. Similar spp. Rusty-fronted Canastero A. ottonis has a rufous forehead and striped neck. Sharp-billed Canastero A. pyrrholeuca is similar but greyer and doesn't occur in range. Cordilleran Canastero A. modesta always shows streaking on neck and breast. Voice Song an accelerating series of fast clear notes, slightly rising in pitch. Call a soft short slightly descending tuírrrrr trill. Hints Concealed in dense vegetation, best located by voice.
Text account compilers
Butchart, S., Gilroy, J., Hjarsen, T., Mayer, S., Mazar Barnett, J., Pearman, M. & Sharpe, C.J.
BirdLife International (2023) Species factsheet: Asthenes heterura. Downloaded from http://www.birdlife.org on 23/03/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/03/2023.