Archived 2012-2013 topics: Bolivian Spinetail (Cranioleuca henricae): uplist to Critically Endangered?

BirdLife species factsheet for Bolivian Spinetail Bolivian Spinetail Cranioleuca henricae occurs in dry valleys on the east slope of the Andes in west Bolivia (Cochabamba and La Paz). It is currently listed as Endangered under criterion B1ab(i,ii,iii,v) because it has a small range, Extent of Occurrence (EOO) previously estimated at 3,000 km2,in which suitable habitat is severely fragmented and continuing to decline. The only viable populations known are in the río Cotacajes basin, with one below Inquisivi, La Paz, where it is common, one at Cotacajes, Cochabamba, where it is uncommon, and two at Machaca and Cuti, both Cochabamba (Maijer and Fjeldså 1997, Herzog et al. 1999, S. K. Herzog in litt. 1999, 2007). Records of 1-2 individuals come from Churupampa and nearby Sorata in the río Consata basin (Maijer and Fjeldså 1997, Lowen and Kennedy 1999), and Mecapaca in the upper río La Paz basin, La Paz (B. Hennessey per S. K. Herzog in litt. 1999). 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). Searches in the Consata basin (where very little suitable habitat remains) and in the lower río La Paz basin have not revealed further localities (S. K. Herzog in litt. 1999, 2007). One of the most recently discovered populations is highly threatened by a road construction project which will make the area directly accessible from La Paz (S. K. Herzog in litt. 1999, 2007). The stronghold of this species was suggested to be in the dry forest surrounding Machaca (F. Rheindt in litt. 2012). However, a recent visit to this area identified only two suitable gulleys, each home to no more than 10 mature trees (F. Rheindt in litt. 2012). A group of 3-4 birds was found in the gulley closest to town at about 2800m, but none were found at the more distant, higher gulley at c. 2950m, or in any of the low disturbed scrub that now covers the hillsides (F. Rheindt in litt. 2012). The global population was previously estimated to number 1,000-2,499 mature individuals, based on an assessment by S. K. Herzog (in litt. 1999) that numbers are probably below 3,000 mature individuals. However, the almost complete lack of suitable habitat within its apparent stronghold, together with the low encounter rate in Machaca and other areas, may indicate that the species is more severely threatened than previously thought. If there is sufficient evidence to suggest that the species’s population is <250 mature individuals, and all subpopulations are ≤50 mature individuals, this species would warrant uplisting to Critically Endangered under criterion C2a(i) of the IUCN Red List. Further information is required on this species’s population size, distribution and the size of the largest subpopulation. Any additional comments on its proposed uplisting are welcome. References; Herzog, S. K., Fjeldså, J., Kessler, M. and Balderrama, J. A. (1999) Ornithological surveys in the Cordillera Cocapata, depto Cochabamba, Bolivia, a transition zone between humid and dry intermontane Andean habitats. Bulletin of the British Ornithologists’ Club 119: 162-177. Lowen, J. C. and Kennedy, C. P. (1999) Notes on scarce species in La Paz department, Bolivia. Cotinga 12: 82. Maijer, S. and Fjeldså, J. (1997) Description of a new Cranioleuca spinetail from Bolivia and a `leapfrog pattern’ of geographic variation in the genus. Ibis 139: 606-616.

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One Response to Archived 2012-2013 topics: Bolivian Spinetail (Cranioleuca henricae): uplist to Critically Endangered?

  1. Sebastian K. Herzog says:

    In early 2010 Asociacion Armonia carried out a biological/ecological baseline study at four dry forest sites (Kuti, Larimarca, Huancarani, Machaca) in the Cotacajes valley (Cochabamba side, municipio de Independencia), funded by the Agencia Suiza para el desarrollo y la cooperación COSUDE. We used standard point counts (50-m radius), with points at least 250 m apart. At Kuti (1900-2200 m, 24 points) we recorded 27 birds, at Larimarca (2100-2320 m, 12 points) 15 birds, at Huancarani (1990-2230 m, 12 points) 18 birds, and at Machaca (2140-2430 m, 12 points) 19 birds. This adds up to a total of 79 birds at only 4 sites, not including areas between point count stations. So the average number of birds per point (= 0.785 ha) was 1.32, which is an underestimation as almost certainly not all birds present were detected during point counts. Extrapolating that value, a conservative estimate of the average number of birds per ha is 1.68, and 168 birds per km2.

    In a GIS-based analysis with spatially explicit data, Herzog et al. (J. Ornithol. 2012, 153:1189–1202) estimated the species global range size at 1889 km2, eliminating much unsuitable habitat and elevation included in BirdLife’s EOO estimate of 3000 km2. So even if only 1% of its potential range size contained suitable habitat (not yet seriously degraded), we could still expect a global population of around 3000 birds.

    Based on these results I do not think the global population is anywhere near 250 mature individuals. Machaca and nearby Huancarani indeed seem to be the species’ stronghold, and Frank Rheindt was searching for the species too high up the slopes, around the village itself, rather than lower down towards the valley bottom, away from the road, where there is more extensive forest.

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