Black-and-chestnut Eagle Spizaetus isidori


Justification of Red List Category
This species has been uplisted to Endangered on the basis that its declining population is estimated to be very small, with fewer mature individuals than previously thought. The destruction of its montane forest habitat, as well as direct human persecution, are inferred to be driving a continuing decline. Further research is required to elucidate threatening processes and quantify their resulting effects on population trends.

Population justification
The population in Venezuela has been estimated in the low hundreds or perhaps 200 mature individuals (C. J. Sharpe in litt. 2003, 2015), with probably fewer than 250 mature individuals in Bolivia (S. K. Herzog in litt. 2013). The population in Argentina may be small (Ferguson-Lees and Christie 2001), and whilst there is an unquantified number in Peru, it remains rare. Opinions on the population in Colombia vary, with one population alone, in a large stretch of suitable habitat on the eastern slopes of the Andes in Colombia, from Huila to Meta department, thought to support a few hundred individuals (T. Donegan in litt. 2010), compared with an estimate of fewer than 100 adults in the country's total population (C. Márquez in litt. 2012, 2014). The species appears to be common in the Santa Marta mountains and on the western slope of the Los Nevados National Park and around Ucumari and Monterredondo (C. Downing in litt. 2013), although this species is mobile, with the same birds probably recorded multiple times in a single day (C. Márquez in litt. 2014). The population in Ecuador is thought to consist of a maximum of 200 mature individuals (Ridgely and Greenfield 2001). The global population has been variously estimated at more than 1,000 individuals (T. Donegan in litt. 2010, Y. Molina in litt. 2010) or fewer than this (H. Vargas in litt. 2012, C. Márquez in litt. 2014). It is therefore precautionarily placed in the band for 250-999 mature individuals, with no more than 250 mature individuals in each sub-population. Based on this, there are assumed to be c.370-1,500 individuals in total. However, a complete survey of this species throughout its range is needed to accurately quantify its global population.

Trend justification
This species is thought to prefer primary forests (C. J. Sharpe in litt. 2003, T. Donegan in litt. 2010), although it may persist in mosaics of primary and secondary forest with open areas (C. Márquez in litt. 2012). Given habitat loss (Thiollay 1994) and persecution by humans (H. Vargas in litt. 2012) throughout its range, the population is considered to be declining. It has been reported, however, that there has been no discernible decline in records in Risaralda and Magdalena, Colombia, over the past 13-18 years (C. Downing in litt. 2013), thus detailed monitoring is required to quantify the overall population trend.

Distribution and population

This species has an extensive but narrow and altitudinally restricted linear distribution on the coastal ranges of north-central Venezuela (Carabobo and Aragua) and north-eastern Colombia (Santa Marta Mountains), and from the subtropical slopes of the Andes from Venezuela (Mérida and Perijá Mountains) through Colombia, Ecuador and Peru to west-central Bolivia and north-western Argentina (Fjeldså and Krabbe 1990, Thiollay 1994, Roesler et al. 2008, Aráoz et al. in press). It is thought to be rare and patchily distributed but its status is very poorly known (Thiollay 1994, Ferguson-Lees and Christie 2001). The total population is precautionarily estimated to include fewer than 1,000 mature individuals (Ferguson-Lees and Christie 2001, C. Márquez in litt. 2014), with no more than 250 mature individuals in each sub-population.


It is found on heavily forested mountain slopes, probably occurring mostly in large valleys, usually at 1,500-2,800 m, but recorded from sea-level to 3,500 m (Fjeldså and Krabbe 1990, Thiollay 1994). It has been observed in some partially logged tracts of forest, but this is perhaps as a direct result of extensive primary forest loss in the subtropical zone (Thiollay 1994). Despite such observations, it is considered that the species requires some undisturbed primary montane forest in at least part of its large home range (Ferguson-Lees and Christie 2001). It has been recorded feeding on a variety of mammals and birds. Its breeding season in Colombia and Bolivia is thought to be between February and September (Ferguson-Lees and Christie 2001), and in Argentina between May and October (Aráoz et al. in press). Chickens comprised over a third of prey items at one nest in Colombia (Márquez and Delgado 2010), and 9% in Argentina (Aráoz et al. in press).


It apparently requires at least part of its home range to include undisturbed primary forest, which has been subject to huge losses in many parts of its extensive range, primarily owing to conversion for agriculture (Ferguson-Lees and Christie 2001). In Ecuador, montane forests are threatened by logging and mining (G. Buitron in litt. 2014). Persecution has been recorded in Colombia and Ecuador in response to predation of chickens (Márquez and Delgado 2010, Y. Molina in litt. 2010, C. Márquez in litt. 2012, 2014). It is not known how serious a threat this is, but in one Colombian study, eight cases of eagle persecution and killing were noted (Márquez and Delgado 2010). This conflict appears to be increasing (C. Márquez in litt. 2014), and as larger extensions of forest are colonised, eagles may come into more frequent contact with humans and livestock (C. Márquez in litt. 2012, H. Vargas in litt. 2012, Aráoz et al. in press).

Conservation actions

Conservation Actions Underway
It occurs in several national parks and other protected areas in Venezuela, Colombia and Ecuador (C. J. Sharpe in litt. 2003, Y. Molina in litt. 2010, H. Vargas in litt. 2012). A conservation and monitoring project on the east slope of the Eastern Andes of Colombia is seeking to identify priority areas for conservation as well as addressing conflicts between poultry owners and eagles (C. Márquez in litt. 2012). Considered a species of national conservation concern throughout its range (Bierregaard et al. 2014).

Conservation Actions Proposed
Research its ecological requirements and tolerance of habitat fragmentation. Attempt to obtain an accurate global population estimate of this difficult to survey species; national population estimates are urgently needed (Bierregaard et al. 2014). Expand network of protected areas to include large core areas of mountain slope primary forest. Investigate methods to protect backyard chickens from eagle predation (C. Márquez in litt. 2012, H. Vargas in litt. 2012).


Text account compilers
Benstead, P., Calvert, R., Capper, D., Clay, R., Mansur, E., Sharpe, C J, Symes, A., Taylor, J.

Zuluaga, Z., Vargas, H., Sharpe, C J, Molina-Martínez, Y., Herzog, S., Márquez, C., Downing, C., Calderón, D., Donegan, T., Grande, J., Buitron, G.

Recommended citation
BirdLife International (2022) Species factsheet: Spizaetus isidori. Downloaded from http://www.birdlife.org on 24/09/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 24/09/2022.