Grey-backed Hawk Pseudastur occidentalis


Justification of Red List Category
This species has a very small population, which is declining rapidly in response to continuing habitat destruction. Remaining populations are now highly fragmented and most subpopulations are probably extremely small. The species is therefore classified as Endangered.

Population justification
The population density in the Northwest Peru Biosphere Reserve was calculated to be 0.65 individuals per km2, with the population of the study area estimated at 136 individuals (Piana 2016). The population is estimated to number 250-999 mature individuals based on an assessment of known records, descriptions of abundance and range size. This is consistent with recorded population density estimates for congeners or close relatives with a similar body size, and the fact that only a proportion of the estimated Extent of Occurrence is likely to be occupied. This estimate is equivalent to 375-1,499 individuals in total, rounded here to 350-1,500 individuals.

Trend justification
A moderately rapid and ongoing population decline is suspected to be occurring in response to continuing habitat destruction and fragmentation over the period of the last three generations.

Distribution and population

Pseudastur occidentalis is confined to west Ecuador (Esmeraldas, Manabí, Pichincha, Los Ríos, Azuay, El Oro, Guayas, Cañar and Loja) and adjacent north-west Peru (Tumbes). Most records refer to one or two pairs per site and, if these fragmented outposts represent stranded birds rather than dispersive resilience, viable populations may survive at only a few sites. Notable amongst these are Machalilla National Park, Mache-Chindul Ecological Reserve (K. Berg verbally 2002), the largely unprotected IBA Verde-Ónzole-Cayapas-Canandé (EC005 [Freile and Santander 2005b]) (O. Jahn in litt. 2007, P. Mena V. in litt. 2007), the Buenaventura reserve (R. S. Ridgely per J. F. Freile in litt. 2012), and surrounding areas in Piñas, Bosque Protector Cerro Blanco and Manta Real (Vargas 1995), Ecuador, the northern portion of the Cerros de Amotape National Park, the Tumbes National Reserve (now part of the Northwest Peru Biosphere Reserve [Piana 2016]) and the Angostura-Faical Regional Conservation Area in Tumbes, Peru (R. Piana in litt. 2012), which is relatively secure owing to its remoteness (J. F. Freile in litt. 2000). At this moment, it is unclear if the newly discovered population in the humid lowlands to the far north of the Río Esmeraldas, was previously overlooked or represents a recent expansion the species's range (O. Jahn in litt. 2007, P. Mena V. in litt. 2007). Although it is possible that the species temporarily benefits from forest fragmentation in that area, deforestation rates in Esmeraldas are so high that almost total deforestation might occur within one or two decades (O. Jahn in litt. 2007, P. Mena V. in litt. 2007).


It inhabits dry deciduous and humid evergreen forests, but is more frequently recorded in the latter. This species can be found feeding in fairly degraded habitats in the environs of Machalilla National Park (J. F. Freile in litt. 2000) and at forest edges in Esmeraldas (O. Jahn in litt. 2007, P. Mena V. in litt. 2007)), Piñas and Manta Real (Vargas 1995), and the Tumbes National Reserve (Piana and Marsden 2012). It mostly occurs at elevations of 100-1,400 m, but occasionally as high as 2,900 m (Best and Kessler 1995). It feeds on lizards, snakes, crabs, rodents, small birds, earthworms, frogs and large insects (Vargas 1995). Breeding appears to take place year round  and nests and eggs were described by Vargas (1995)  Eight nests were located in Piñas and two in Bosque Protector Cerro Blanco, Ecuador (Vargas 1995).


There has been extensive habitat destruction and fragmentation throughout its range, with over 90% of west Ecuador now deforested. Clearance for timber and agriculture, and intense grazing pressure from goats and cattle in the forest understorey, have led to west Ecuador's forests becoming one of the world's most threatened ecosystems (Parker and Carr 1992). Even Machalilla National Park is affected by settlement, cutting, livestock-grazing and hunting. Human persecution is a major threat in south-western Ecuador (Vargas 1995). In Esmeraldas, annual deforestation rates of lowland evergreen forest were 3.8% and accumulated loss of primary forest >38% in the last decade (Cárdenas 2007). Colonisation and land development are progressing through infrastructural improvement, particularly the expansion of road networks, and in turn are increasing the impact of logging, cattle-ranching, oil palm planting and hunting (Cárdenas 2007, O. Jahn in litt. 2007, P. Mena V. in litt. 2007). The Mache-Chindul Ecological Reserve is increasingly affected by illegal logging, hunting, and other activities (O. Jahn in litt. 2007). The Tumbes National Reserve and the Angosturas-Faical Regional Protected Area are subject to forest clearing for the establishment of cattle pasturelands and are affected by timber extraction and hunting (Piana and Marsden in press 2012).

Conservation actions

Conservation Actions Underway
CITES Appendix II. In Ecuador, the species occurs in Machalilla National Park, Mache-Chindul, Manglares Churute and Arenillas Ecological Reserves, Pacoche Wildlife Reserve and the Northwest Peru Biosphere Reserve, as well as the Chongón-Colonche Protection Forest (which is the nucleus of a reforestation project) (E. Horstmann in litt. 2000, O. Jahn in litt. 2007, P. Mena V. in litt. 2007). Six pairs may breed in the Buenaventura reserve (R. S. Ridgely per J. F. Freile in litt. 2012).  It is also found in other small private reserves like Jorupe, Cantalapiedra, Loma Alta, La Ceiba, El Aromo, Lalo Loor, Caimito and Silanche (J. F. Freile in litt. 2012). Reforestation is under way in several private reserves such as Buenaventura, Canande, Jorupe and Lalo Loor (Vargas in litt. 2012). In Peru, it is found in Cerros de Amotape National Park, Tumbes National Reserve (now part of the Northwest Peru Biosphere Reserve) and the Angostura-Faical Regional Conservation Area in Tumbes (R. Piana in litt. 2012).

Conservation Actions Proposed
Census the species in each of the habitat fragments where it occurs (T. S. Schulenberg in litt. 1999). Map the forest patches of the Cordillera Chongón-Colonche to identify further sites for protection (E. Horstmann in litt. 2000). Effectively protect habitat in  Cerros de Amotape National Park, Tumbes National Reserve, Angostura-Faical Regional Conservation Area and Machalilla National Park (R. Piana in litt. 2012). Designate the Awá Reserve, Cotacachi-Cayapas Ecological Reserve, Awacachi Corridor, Gran Reserva Chachi, and Canandé Reserve, including the Río Santiago, Cayapas, Ónzole, and Hoja Blanca drainages, as a biosphere reserve (O. Jahn in litt. 2007, P. Mena V. in litt. 2007). Consolidate protection of the Mache-Chindul Ecological Reserve through law enforcement against illegal logging, hunting, and colonization inside the reserves and sustainable management projects in its buffer zone (O. Jahn in litt. 2007). Search for the species in forest remnants in coastal Nariño, Colombia (O. Jahn in litt. 2007), and forested areas south of the Cerros de Amotape National Park towards the border with Ecuador (R. Piana in litt. 2012)..


45-48 cm. Medium-sized, black-and-white hawk. Adult has blackish mantle and wings. Grey head and nape, streaked white. White tail with broad, black subterminal band. White underparts. Yellow legs. Juvenile browner above with dusky streaking on mantle. Similar spp. Red-backed Hawk Buteo polysoma is paler grey above with red mantle and narrower subterminal band.Voice: A loud husky scream shreeeyr often repeatedly, primarily in flight, most similar to White Hawk's Leucopternis albicollis (Coopmans et al. 2004).


Text account compilers
Benstead, P., Isherwood, I., Jahn, O., Sharpe, C J & Symes, A.

Arosemena, J., Berg, K., Freile, J., Horstman, E., Jahn, O., Mena-Valenzuela, P., Schulenberg, T., Piana, R. & Vargas, H.

Recommended citation
BirdLife International (2022) Species factsheet: Pseudastur occidentalis. Downloaded from http://www.birdlife.org on 08/12/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 08/12/2022.