SPECIES

Black-and-chestnut Eagle Spizaetus isidori Scientific name definitions

Tomás Rivas-Fuenzalida, Juan M. Grande, Sebastián Kohn, Felix Hernán Vargas, and Santiago Zuluaga Castañeda
Version: 2.0 — Published November 23, 2022

Demography and Populations

Measures of Breeding Activity

Age at First Breeding

Black-and-chestnut Eagle can begin its first breeding attempts at three years of age (TRF, unpublished data).

Clutch Size

All recorded clutches have been of a single egg.

Life Span and Survivorship

A study conducted between 2015 and 2020 in Colombia and Argentina found juvenile survival is low during their natal dispersal. Only two of six tagged juvenile eagles survived their dispersal through fragmented landscapes (Zuluaga et al., unpublished data). Adult survival is probably higher, though this has not been studied. However, it has been shown that increased habitat fragmentation can increase both adult and juvenile mortality (55).

Disease and Body Parasites

Information needed.

Causes of Mortality

Exposure

A chick died after being repeatedly pulled from the nest by the adult male (SK, unpublished data).

Direct Human Impacts

The main cause of mortality of adults and juveniles is human persecution in retaliation for poultry predation (i.e., human-eagle conflict), although poaching and electrocutions are also major causes of mortality (48, 51, 55). In Colombia, at least 80 eagles were found dead in the last 80 years; of these, ~47 were shot in retaliation for poultry predation (51). In Ecuador, at least two individuals were found electrocuted under power lines (SK, unpublished data), and a fledgling was injured when its nest tree was felled when heavy machinery was used to build a road; it later died of its injuries (TRF, unpublished data). In Peru, at least 30 individuals were killed in the last 20 years (3 adults and 26 juveniles were shot and a juvenile was poisoned; Rivas-Fuenzalida and Orizano, unpublished data). In northwest Argentina, one juvenile was shot by locals in 2019 (SZ, unpublished data) after 50 years without evidence of human persecution of the species. The first two individuals scientifically collected in this country were shot by hunters in the mid-late 1950's.

Additionally, a 2022 study in Colombia and Ecuador found evidence of poaching in 59% of the sampled nests (4 of 6 nests in Colombia and 12 of 21 in Ecuador) and across eight geographical jurisdictions of government authority (54). Similar results were found in the central Andes of Peru, where 19 of the 35 known breeding territories showed evidence of poaching (TRF, unpublished data).

Population Spatial Metrics

Home Range

Information on one adult female equipped with a satellite transmitter in Argentina indicated a home range (95% kernel density) of ~7,000 ha (SZ, JMG, unpublished data). Direct observations in Peru suggest a home range of ~5,000 ha for a breeding pair (TRF, unpublished data).

Spacing of Breeding Territories

In Colombia, nests could be spaced several kilometers from one another, especially in habitats that have been highly disturbed by humans. In the eastern slopes of Ecuador (Tunguragua region), the mean minimum inter-nest distance was 4.64 km (n = 15; Rivas-Fuenzalida et al., unpublished data). Similar inter-nest distances were found in central Peru, with a mean minimum inter-nest distance of 5.4 km (n = 17; Rivas-Fuenzalida et al., unpublished data). In central Peru (Junin region), a pair defended an area of about 23 km2 against conspecific intruders from neighboring territories (TRF, unpublished data).

Population Status

Numbers

The global population is currently estimated to be between 370 and 1,500 total individuals (56).

In Colombia and Venezuela, it was estimated that 100 km2 of mature forest are necessary to maintain a single breeding pair (57, 58 ). In southeast Ecuador, 15 pairs were observed in 543 km2 in the Baños de Agua Santa Valley (Tunguragua region), giving a density of 1 pair / 36.2 km2 (Rivas-Fuenzalida et al., unpublished data). In central Peru, mean breeding pair density was estimated at 1 pair / 39.3 km2 (Rivas-Fuenzalida et al., unpublished data). However, new studies of population densities are needed for other areas throughout its distribution.

Trends

The species is experiencing a population decline owing to habitat destruction and direct persecution (56).

Population Regulation

Young individuals are expelled from good quality habitats by territorial adults, which probably cause these juveniles to visit more anthropogenic habitats where they are consequently more prone to human persecution.

Limiting factors may include the lack of large emergent trees for nesting due to selective logging and low suitable food supply due to illegal hunting, habitat loss, and fragmentation.

Recommended Citation

Rivas-Fuenzalida, T., J. M. Grande, S. Kohn, F. H. Vargas, and S. Zuluaga Castañeda (2022). Black-and-chestnut Eagle (Spizaetus isidori), version 2.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.baceag2.02