BirdLife species factsheet for Slaty Becard
Slaty Becard (Pachyramphus spodiurus) occurs in the Tumbesian and Chocó regions of western Ecuador and north-western Peru. It occurs mostly below 750 m, but locally ranges as high as 1,100 m. It inhabits lowland deciduous, semi-deciduous and humid woodland, but also shrubby clearings with scattered tall trees, patches of evergreen shrubbery and second growth within humid forest (Best and Kessler 1995, Clements and Shany 2001, Ridgely and Greenfield 2001). It forages in the canopy of tall trees. The species occupies a very small and fragmented range. Its population is estimated to number 600-1,700 mature individuals. Throughout the range, Slaty Becard is thought to be genuinely rare, and the paucity of recent records suggest that the species has suffered a serious decline, which is still ongoing.
Habitat loss and fragmentation are assumed to be the main drivers of the population decline. Throughout its range, forests are being rapidly destroyed, degraded and fragmented (Mobley 2018). In lowland western Ecuador, deforestation rates between 1958 and 1988 amounted to 57% per decade (Dodson and Gentry 1991). Forest loss is still ongoing, so that virtually all lowland forest outside protected areas is feared to disappear soon (Mobley 2018).
Forests are cleared for timber extraction and cattle farming. Even within protected areas, forests are lost through selective logging of valuable trees and persistent grazing by goats and cattle (S. Crespo in litt. 2012), the latter causing disturbance and degradation of the understorey in remaining deciduous woodland. Further threats are encroachment and the expansion of agricultural fields. Even though these imminent threats have strong negative impacts on the species and its range, Slaty Becard may show some tolerance of forest degradation. Occasionally, it has been reported to persist in substantially degraded areas and secondary growth (Ridgely and Greenfield 2001).
Currently, Slaty Becard is listed as Endangered under Criterion B1ab(i,ii,iii,v), indicating a very small Extent of Occurrence (EOO) and declines in population size and habitat availability. Following IUCN guidelines, the EOO for this species has been re-calculated using a Minimum Convex Polygon, which is “the smallest polygon in which no internal angle exceeds 180 degrees and which contains all the sites of occurrence” (IUCN 2001, 2012, Joppa et al. 2016). After re-calculating the EOO for Slaty Becard, this species appears to warrant a change in Red List status. Therefore, we present here our reassessment against all criteria for the species.
The initial topic on this analysis can be found here.
Criterion A – Global Forest Watch measures forest loss within this species’s range between 2001 and 2017 as c.1,440 km2. This roughly equates to a rate of forest loss of 4.2% over three generations (13.8 years) for this species, with the assumption that it has continued at the same rate to the present day. Slaty Becard, however, appears to be able to tolerate a certain level of deforestation, as it is found in disturbed areas and secondary growth. Nevertheless, while it depends on the presence of tall trees for foraging, the species is further affected by selective logging, agricultural expansion and the degradation of understory caused by cattle grazing. Thus, it is conceivable that the population change is roughly proportional to the rate of forest cover change. Tentatively, the rate of population decline is placed here in the band 1-9% over three generations, and therefore Slaty Becard may be considered Least Concern under Criterion A.
Criterion B – Using a Minimum Convex Polygon, the Extent of Occurrence (EOO) has been calculated as 77,300 km2. This is far too large for listing the species as Vulnerable and therefore, Slaty Becard may be listed as Least Concern under this criterion. The Area of Occupancy has not been calculated; thus, the species cannot be assessed against Criterion B2.
Criterion C – The population of Slaty Becard is estimated to number 600-1,700 mature individuals. This may warrant listing the species under Criterion C, given it is considered to be declining, as long as other conditions are met. As the rate of population decline is suspected based on the rate of forest loss, Slaty Becard does not warrant listing as threatened under Criterion C1.
Given its highly localized occurrence throughout a severely fragmented distribution range, the species likely forms several subpopulations. However, considering the small population size it can be assumed that no subpopulation consists of more than 1,000 mature individuals. Therefore, Slaty Becard may be listed as Vulnerable under Criterion C2a(i).
Criterion D – The population size of this species is estimated at 600-1,700 mature individuals. Under the assumption that the population size is close to the lower band of the estimate and thus falling below 1,000 mature individuals, the species may be listed as Vulnerable under Criterion D1.
Criterion E – To the best of our knowledge no quantitative analysis of extinction risk has been conducted for this species. Therefore, it cannot be assessed against this criterion.
Therefore, it is proposed that Slaty Becard (Pachyramphus spodiurus) be listed as Vulnerable under Criteria C2a(i); D1. We welcome any comments on this proposed listing.
Please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of its Red List status. Therefore, please make sure your comments are relevant to the discussion outlined in the topic.
An information booklet on the Red List Categories and Criteria can be downloaded here and the Red List Criteria Summary Sheet can be downloaded here. Detailed guidance on IUCN Red List terms and definitions and the application of the Red List Categories and Criteria can be downloaded here.
Best, B.J.; Kessler, M. 1995. Biodiversity and Conservation in Tumbesian Ecuador and Peru. BirdLife International, Cambridge, U.K.
Clements, J.F.; Shany, N. 2001. A Field Guide to the Birds of Peru. Lynx Edicions, Barcelona, Spain.
Dodson, C.H.; Gentry, A.H. 1991. Biological extinction in western Ecuador. Annals of the Missouri Botanical Garden 78: 273-295.
Global Forest Watch. 2014. World Resources Institute. www.globalforestwatch.org (Accessed 14 September 2018).
IUCN. 2001. IUCN Red List Categories and Criteria: Version 3.1. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K.
IUCN. 2012. IUCN Red List Categories and Criteria: Version 3.1. Second edition. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K. www.iucnredlist.org/technical-documents/categories-and-criteria.
Joppa, L.N.; Butchart, S.H.M.; Hoffmann, M.; Bachman, S.P.; Akçakaya, H.R.; Moat, J.F.; Böhm, M.; Holland, R.A.; Newton, A.; Polidoro, B.; Hughes, A. 2016. Impact of alternative metrics on estimates of extent of occurrence for extinction risk assessment. Conservation Biology 30: 362-370.
Mobley, J. 2018. Slaty Becard (Pachyramphus spodiurus). In: del Hoyo, J.; Elliott, A.; Sargatal, J.; Christie, D.A.; de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona, Spain. https://www.hbw.com/node/57537 (Accessed 14 September 2018). Ridgely, R.S.; Greenfield, P.J. 2001. The Birds of Ecuador: Status, Distribution and Taxonomy. Cornell University Press and Christopher Helm, Ithaca, U.S.A. and London, U.K.