Justification of Red List Category
This species is listed as Vulnerable because it has a small range, in which suitable habitat is declining in quantity and quality. The population is very small. The species occurs in two disjunct subpopulations, but the status of one of them is unclear. The species may qualify for a higher threat category in the future.
Field surveys revealed a population density of 168 individuals/km2 (S. K. Herzog in litt. 2013). The area of mapped range covers c.1,390 km2. Assuming that only 1% of this area contains suitable habitat for the species, the extrapolation of the population size results in an estimate of c.2,330 individuals. This roughly equates to 1,500 mature individuals. Given the apparent rarity of the species near Sorata, the population estimate may need to be corrected if more recent survey data from the area becomes available.
As a consequence of the destruction and degradation of its habitat, the species is suspected to be undergoing a decline, the rate of which has not been directly estimated. A remote sensing study found that no forest was lost within the range over the last three generations (Tracewski et al. 2016). Apart from woodland, the species also occupies shrub and brushland (Remsen and Sharpe 2018), but there is no information about the rate of conversion of this habitat.
Cranioleuca henricae occurs in dry valleys on the east slope of the Andes in west Bolivia (Cochabamba and La Paz). The only populations known are in the río Cotacajes basin near Inquisivi and the río Consata basin near Sorata (Maijer and Fjeldså 1997; Herzog et al. 1999; S. K. Herzog in litt. 1999, 2007). The species has been found to be abundant in the Cotocajes valley (Seeholzer et al. 2015). A record of a Cranioleuca sp. in suitable habitat at Saila Pata in the río Cotacajes basin may be attributable to this species (N. Krabbe per S. K. Herzog in litt. 1999). Records of 1-2 individuals came from Churupampa and nearby Sorata in the río Consata basin (Maijer and Fjeldså 1997, Lowen and Kennedy 1999). Searches in the río Consata basin, where very little suitable habitat remains, have not revealed further localities (S. K. Herzog in litt. 1999, 2007). The species has not been observed in the past years in the Consata basin and the status of the population there is unclear; however no targeted surveys have been carried out in recent years (S. K. Herzog in litt. 2019). A record from Mecapaca in the upper río La Paz basin is unconfirmed and likely erroneous (S. K. Herzog in litt. 2019).
The species occupies the understorey of dry, seasonally deciduous montane woodland and forest in rain-shadow valleys at c.1,800-3,300 m (Maijer and Fjeldså 1997, Herzog et al. 1999, Remsen and Sharpe 2018). It may also be found in low, bushy vegetation in cleared areas adjacent to forest (Remsen & Sharpe 2018). Rarely, it ventures into plantations. It has been hypothesised that Bolivian Spinetail depends on the epiphytic ‘grey beard’ bromeliad for nesting (A. Hennessey in litt. 2006). A possible juvenile and apparent pairs have been observed in January, while mixed-species feeding parties are joined in the dry season (the austral winter) (Maijer and Fjeldså 1997, Herzog et al. 1999).
Much suitable habitat has long been destroyed or severely degraded due to anthropogenic impact (Maijer and Fjeldså 1997, S. K. Herzog in litt. 1999, 2007). For centuries, woodland within the range has been cut for firewood and charcoal production, which greatly reduces the abundance of the ‘grey beard’ bromeliad (Maijer and Fjeldså 1997, S. K. Herzog in litt. 1999, 2007). Although many older trees with the 'grey beard' bromeliad remain in the Cotojaces basin, habitat regeneration is impeded by heavy overgrazing, burning and clearance for agriculture (Maijer and Fjeldså 1997, S. K. Herzog in litt. 1999, 2007). The conversion of native vegetation into Eucalyptus plantations, combined with the destruction of native vegetation and high grazing pressure, has caused hydrological changes leading to massive soil erosion and landslides (S. K. Herzog in litt. 1999, 2007). The species’s stronghold near Inquisivi in La Paz department may be extirpated by landslides by 2050 or sooner (S. K. Herzog in litt. 1999, 2007). The expansion of the road network threatens the remaining habitat by facilitating access to the area and exploitation of the forest for charcoal production (S. K. Herzog in litt. 1999, 2007). Climate change is likely to significantly reduce this species’s range (del Rosario Avalos and Hernández 2015).
Conservation Actions Underway
Considered Endangered at the national level in Bolivia (Ministerio de Medio Ambiente y Agua 2009). Targeted searches have resulted in some of the most recent records, but also a number of negative results from apparently suitable habitat (Herzog et al. 1999, S. K. Herzog in litt. 1999, 2007). It is not currently known from any protected areas (Rocha and Balderrama 2009). Proposals have recently been made to protect the Machaca stronghold by developing a long-term conservation strategy working closely with the local community and involving local environmental education, sustainable development workshops, agricultural assessment and development, and the promotion of the area as a birdwatching attraction; with the eventual aim of protecting a core area as a reserve (S. K. Herzog in litt. 1999, 2007).
14.5 cm. Rufous and greyish-olive spinetail with whitish supercilium. Rufous crown, wings and tail, with brownish olive nape, mantle and rump. Prominent whitish supercilium extending from upper lores to rear of crown. Greyish cheek, face, and underparts, except olive-washed vent and rear flanks. Olive-yellow legs and feet. Pinkish deep-based bill with sooty culmen and tip. Voice Short and long songs, in accelerating and descending series, lasting up to 13.5 seconds. Range of single, double and triple-note calls, or even 3-5 notes, usually given in alarm or excitement.
Text account compilers
Symes, A., Taylor, J., Hermes, C., Sharpe, C.J., Stuart, T., Pople, R.
Diaz, D., Hennessey, A.B., Herzog, S.K., Krabbe, N., Lane, D., Rheindt, F. & Soria, R.W.
BirdLife International (2023) Species factsheet: Cranioleuca henricae. Downloaded from http://www.birdlife.org on 24/03/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 24/03/2023.