Introduction

Conflicts over wildlife, often called human-wildlife conflicts, are complex, particular, and widely distributed (Zimmermann et al., 2020). These are of great concern in the case of threatened species and those with declining populations that could be rapidly eliminated at the landscape scale as a result of these conflicts (Zimmermann et al., 2021). Human persecution to mitigate or prevent the predation of domestic animals is an important threat to Neotropical eagles, especially those of larger size (Sarasola et al., 2018). For example, human persecution of the Harpy Eagle (Harpia harpyja) in Brazil is an important threat to the species (Miranda et al., 2021) and such persecution constitutes a relevant threat to the Chaco Eagle (Buteogallus coronatus) in Argentina (Barbar et al., 2016).

The Black-and-chestnut Eagle (Spizaetus isidori) inhabits dense mountain forests throughout the Andes, as well as in the Sierra Nevada de Santa Marta (Ferguson-Lees & Christie 2001). Despite this wide latitudinal distribution, studies of the diet of this species have only been published in Colombia and Argentina (Zuluaga & Echeverry-Galvis 2016; Aráoz et al., 2017; Restrepo-Cardona et al., 2019). It feeds on a wide variety of prey, including arboreal mammals and large birds. Poultry is a relatively important prey in its diet, with frequency ranges of 9 to 31% and biomass contributions of 12 to 47% of the total prey consumed (Zuluaga & Echeverry-Galvis 2016; Restrepo-Cardona et al., 2019).

With a total population of fewer than 1000 adult individuals, the Black-and-chestnut Eagle is listed as an Endangered species at the global level (BirdLife International, 2022a). However, despite its concerning conservation status, there have been no quantitative evaluations of the threats faced by the species throughout its distribution. Recent data in Colombia indicate that human persecution as retaliation or as a preventive measure against poultry predation is a relevant cause of mortality in the species (Restrepo-Cardona et al., 2020). In Ecuador, it is unknown whether the underlying causes for human persecution of the Black-and-chestnut Eagle are similar to those found in Colombia, although one recent study suggests that the situation could be very similar in the two countries (Zuluaga et al., 2021b).

Threat evaluation is a central planning component for biodiversity conservation (Groom et al., 2006). As part of the management of conflicts between humans and the Black-and-chestnut Eagle, it is important to quantitatively examine human persecution of the species (Restrepo-Cardona et al., 2020). The purpose of this study was to analyze the human persecution of the Black-and-chestnut Eagle as retaliation or as a preventive measure against poultry predation, as well as other threats that were found to affect the species in Ecuador and Colombia in the period 2000 to 2022. In addition, we explore the age differences among affected eagles. Our hypothesis is that human persecution prevails in the northern Andes as an important threat to the conservation of the Black-and-chestnut Eagle. This paper presents the first records for Ecuador, as well as new records for Colombia and cases published in the literature.

Methods

Results

We found a total of 96 Black-and-chestnut Eagles affected by different threats in the northern Andes in the period 2000 to 2022. The unpublished records included 50 cases (38 in Ecuador and 12 in Colombia). The published records comprised 46 cases of Black-and-chestnut Eagles affected by different threats (1 in Ecuador and 45 in Colombia) (Table 1).

Table 1.

Records of Black-and-Chestnut Eagles (Spizaetus isidori) Affected by Several Threats in the Northern Andes (Ecuador and Colombia), in Chronological Order Between 2000 and 2022.

Immature eagles were affected by the different threats to a greater extent than adult individuals (70 immatures and 23 adults) (X² = 23.75, df = 1, p < 0.05; n = 93). Age of three individuals was undetermined. Sex was not determined in the majority of the eagles affected by the different threats (80 of 96). In cases where it was possible to determine this parameter, nine females and seven males were found. The eagles were affected to the greatest extent by shooting with firearms (57 of 96) (X² = 9.11, df = 1, p < 0.05; n = 86), followed by illegal capture (15 of 96) and electrocution (9 of 96). In addition, we found that two chicks had fallen from the nest, one eagle had been stabbed with a sharp weapon, one had been hit by a vehicle and another had been killed by an adult Black-and-chestnut Eagle. For 10 individuals, the cause of affectation was not determined (Table 1).

Human persecution as retaliation or as a preventive measure against poultry predation was the motive in 81% (46 of 57) of the cases of Black-and-chestnut Eagles that had been shot, 67% (10 of 15) of those captured illegally, 30% (3 of 10) of those for which the cause of affectation could not be determined and for one individual that had been stabbed. Illegal trafficking was the motive in 20% (3 of 15) of the cases of captured Black-and-chestnut Eagles. A total of 73% of the cases (70 of 96, mean: 8 eagles per year) of Black-and-chestnut Eagles suffering different threats occurred between 2014 and 2022, while the remaining cases occurred between 2000 and 2013 (27%, mean: 1.8 eagles per year) (Table 1).

Forty-one percent (39 of 96) of the total number of Black-and-chestnut Eagles affected by different threats was reported in Ecuador. Among these, 51% were shot, 31% were affected by other threats and for seven eagles it was not possible to determine the cause of affectation. The 39 records come from five provinces, mainly Morona Santiago (18 cases, 46%), followed by Napo (10 cases, 26%), Pichincha and Tungurahua (5 cases in each province), and a single case in Carchi. In 61% of the cases, the cause was human persecution of the Black-and-chestnut Eagle as retaliation or as a preventive measure against poultry predation (Table 1; Figure 1).

Figure 1.

Number of Black-and-chestunt Eagles (Spizaetus isidori) affected by several threats in the northern Andes (Ecuador and Colombia) between 2000 and 2022. The polygons correspond to provinces in Ecuador and departments in Colombia.

Fifty-nine percent (57 of 96) of the total number of Black-and-chestnut Eagles affected by different threats was reported in Colombia. Among these, 64.9% were shot, 31.5% were affected by other threats and for two eagles it was not possible to determine the cause of affectation. The 57 records came from 13 departments, mainly Huila (15 cases, 26.3%), followed by Cundinamarca (7 cases, 12.2%), Boyacá and Tolima (5 cases in each department), Antioquia, Quindío and Putumayo (4 cases in each department), Meta and Cesar (3 cases in each department), Norte de Santander, Magdalena and Risaralda (2 cases in each department), and a single case in Cauca. In 63% of the cases, the cause was human persecution of the Black-and-chestnut Eagle to mitigate or prevent predation of poultry (Table 1; Figure 1).

Discussion

We analyzed records of 96 Black-and-chestnut Eagles affected by different threats in the northern Andes in the period 2000 to 2022. Human persecution of the Black-and-chestnut Eagle as retaliation or as a preventive measure against poultry predation was the motive in 81% of the cases of shot eagles and 67% of those captured illegally. The proportion of cases of Black-and-chestnut Eagles affected by different threats differed among ages. Seventy-three percent of the cases of eagles suffering different threats occurred between 2014 and 2022 (Table 1).

Human persecution is a critical problem for the conservation of raptors worldwide, which can cause declines in their populations and even the extinction of species (Madden et al., 2019; Newton, 2020; BirdLife International 2022b). It is of great concern that, from 2000 to 2022, at least 72 Black-and-chestnut Eagles were hunted or captured illegally in the northern Andes (Table 1). Studies exploring the impact of human persecution on raptors indicate that even relatively low rates of hunting can slow down the rate of population growth, rendering the species more susceptible to other potential threats (Newton, 2020). As forest cover decreases in the breeding territories of the Black-and-chestnut Eagle, the importance of poultry, mainly chickens (Gallus gallus), in their diet increases (Restrepo-Cardona et al. 2019) and, thus, the likely of eagles to be hunted in retaliation by poultry predation too (Restrepo-Cardona et al., 2020; Zuluaga et al., 2021a,b). The high levels of deforestation in the northern Andes (e.g., Etter et al., 2006; Sierra et al., 2021), combined with human persecution of the species, could therefore cause the rapid loss of population of the Black-and-chestnut Eagle in this geographical region.

Human persecution to mitigate or prevent predation of poultry affects Black-and-chestnut Eagles differentially according to age. We found a higher proportion of immature eagles shot or illegally captured in the northern Andes, compared to adult eagles (Table 1). This could translate into lower rates of recruitment of reproductive adults. The higher proportion of immature shot and captured Black-and-chestnut Eagles may be a consequence of the fact that, in the nests of this species in Andean mountains of Colombia, poultry was a prey frequently given by the parent eagles to their chicks (Restrepo-Cardona et al., 2019). This may lead to immature individuals being more likely to prey on poultry and thus be more vulnerable to human persecution.

Control of predators using firearms is a particularly important threat to the conservation of Neotropical eagles. This cause of affectation is especially high for the Black-and-chestnut Eagle in the northern Andes, where at least 57 eagles were shot between 2000 and 2022 (Table 1). Similarly, in Ecuador, Colombia, Panama, and Belize, 35 Harpy Eagles were shot between 1998 and 2019 (Giraldo-Amaya et al., 2021) and, in Argentina, 16 Chaco Eagles were shot between 1999 and 2014 (Barbar et al., 2016). According to current environmental legislation in Ecuador and Colombia, the Black-and-chestnut Eagle is a protected species (Renjifo et al., 2014; Freile et al., 2019), and the strict application of these laws is therefore a fundamental tool in preventing the use of firearms against this species in these two countries.

Human persecution has been an important threat to the conservation of the Black-and-chestnut Eagle in the northern Andes over the last 23 years, although this threat has apparently been highest between 2014 and 2022 (Table 1). However, it remains unclear whether this finding is due to a real increase in events of human persecution of the Black-and-chestnut Eagle or to an increase in the number of people studying the species in these countries (Renjifo et al., 2014; Zuluaga & Echeverry-Galvis 2016; Restrepo-Cardona et al., 2019, 2020, Zuluaga et al., 2021a,b, 2022). The data presented in this study were obtained from heterogeneous sources of information and it is therefore important to consider their limitations in terms of reliably determining if there has been a true increase in human persecution of the species from 2014 onwards. Considering these limitations, we did not make comparisons between the numbers of Black-and-chestnut Eagles affected by different threats over time or between countries. Despite these limitations, our analysis provides a good indication of the minimum number of eagles that could have been injured as a result of different threats affecting this species in the northern Andes.

Implications for Conservation

Human persecution of the Black-and-chestnut Eagle as retaliation or as a preventive measure against poultry predation is a conservation problem widely distributed in the northern Andes. This includes at least four provinces in Ecuador and 12 departments in Colombia (Figure 1). The northern Andes has been estimated to support between 28 and 48% (between 285 to 485 pairs) of the total Black-and-chestnut Eagle population (Renjifo et al., 2014; Freile et al., 2019). We highlight the fact that a greater decline of population of the Black-and-chestnut Eagle in this geographical region, one of the last population strongholds of the species, could have important implications for the Black-and-chestnut Eagle conservation.

Being a highly-mobile species with specific habitat requirements, Black-and-chestnut Eagle can be considered an umbrella species (Bennett et al., 2015; Restrepo-Cardona et al., 2019; Zuluaga et al., 2022). When initiatives to protect particular species, such as umbrella species, are carried out efficiently to support actions that also benefit other species, the benefits for biodiversity are more significant (Bennett et al., 2015). Human persecution, illegal capture and trafficking, electrocution, and collision with vehicles also threaten numerous other wild vertebrates along the Andes (Renjifo et al., 2014; Harfoot et al., 2021; Restrepo-Cardona et al., 2022). For this reason, actions to mitigate and prevent anthropogenic threats to the Black-and-chestnut Eagle can help guide the conservation of other species in the ecosystem.

Human-wildlife conflicts are extremely variable, complex, and defy simple explanations. Patterns in human-wildlife conflicts are valid only for informing actions at a local scale, and it is important not to generalize from case studies (Zimmermann et al., 2020, 2021). Even although each case of conflict is particular and requires a customized solution, the best way to scale up human-wildlife conflict mitigation may by practicing and improving effective processes for sustainable, community-focused conservation collaborations (Zimmermann et al., 2021). Evidence-based management actions are key for mitigating conflicts between people and the Black-and-chestnut Eagle and eliminate human persecution of the species in the northern Andes (Restrepo-Cardona et al., 2020). These actions could include the strengthening of technical capacities of rural communities, such as bird watching tourism that may create benefits to local people, tourists and eagles (Miranda et al., 2022). As well as the identification and monitoring of areas with high risk of human-eagle conflict, development of environmental educational programs, maintaining or even increasing forest cover, enhancing populations of the eagle´s arboreal mammal prey species, reducing the exposure of poultry by using enclosures, and offering economic compensation or other economic alternatives when poultry are eaten by the Black-and-chestnut Eagle (Restrepo-Cardona et al., 2019, 2020).