7 thoughts on “Crowned Solitary Eagle (Buteogallus coronatus)”
In Brazil, this species has long been associated with the Cerrado. In fact, this seems to be its main biome of occurrence, apart from the high altitude grasslands of Rio Grande do Sul. However, the species has been increasingly recorded in open areas of the Atlantic Forest biome, expressed in the numerous localities where it has been seen. Even though there are no more accurate censuses, my perception is that the species’ situation is not so serious as to be considered endangered.
In Paraguay the species is considered Vulnerable at the national level (in the most recent assessment, in 2017) due to a suspected ongoing decline of its small population. However, the population size has not been quantified, nor the rate of decline, though it is inferred to be significant due to the high rate of habitat loss (clearance and degradation of Chaco dry forest and Cerrado). There are no systematic studies of direct persecution or electrocution, though both seem likely to occur. The species’ stronghold in the country appear to be the westernmost Dry Chaco (Boqueron department) and northernmost Concepción department.
This species is known under various common and scientific names, which can make collating all relevant information more difficult: Crowned Solitary Eagle or Chaco Eagle in English, and águia-cinzenta in Portuguese. BirdLife treats as Buteogallus coronatus, while in Brazil it is classified as Urubitinga coronata, and it has also been referred to as Harpyhaliaetus coronatus.
This is a rare and threatened bird, and citizen science records may give a misleading impression of abundance, because individuals are very wide-ranging, even more so as juveniles and outside of the breeding season, so all records within a large area (for example, multiple municipalities in WikiAves or multiple locations in eBird), can refer to a single individual or pair. The home range of pairs or adults can be 500-600 kmˆ2, and juveniles can disperse over an area of 12,000 kmˆ2 during their dispersal period (Barbar et al. 2016, Marini et al. 2013). A recent workshop in Brazil brought together researchers on the species from across the species’ range, and the report can be provided (ICMBio 2023).
We can make some calculations based on one of the better-studied parts of this species’ range. In the state of Paraná, Brazil, the population is estimated, based on observations by experienced observers over the past decade, at 20-22 birds, including some that likely range into neighbouring states (Scherer-Neto et al. 2023, ICMBio 2023). As the state of Paraná makes up 2.5% of the species’ EOO (199,298 kmˆ2 out of 8,090,000 kmˆ2), a naive extrapolation of this population would give a total global population of 800-880 birds. We do not know if density in Paraná is representative of other parts of the range. We can make a conservative assumption that it is lower, as most of the western half of the state has been converted to soybeans, maize, pasture and other agricultural uses – however, it should be noted that this is also true of other large areas within this species’ range in the Cerrado, Chaco and Pampas. Even assuming that half of Paraná is entirely unsuitable, and as such that the density in the occupied part of the range is twice as high, extrapolation to the entire range would give an estimate of 1600-1760 birds, and this species would still qualify as Endangered under Criterion C. These calculations also do not allow for the fact that some individuals are immature, so the true number of mature individuals would be lower than this estimate of 800-1760 individuals.
These calculations are quite consistent with those of Marini et al. (2023), who present two estimates of the Brazilian population. One, based on the number of points of occurrence registered in Brazil (around 300), estimates 600-1000 mature individuals in Brazil. Brazil occupies approximately half of the global range of this species, so that would imply a global population of 1200-2000. Marini et al. account for the fact that some territories and individuals will not have been reported, but it is unclear if they account for the possibility that multiple points of occurrence across a wide area can refer to the same individual or pair, as mentioned above, and thus this could be an overestimate. Marini et al. also report an estimate of 150-600 mature individuals in Brazil, which is apparently derived from a previous BirdLife estimate of 250-1000 mature individuals globally, and an estimate that the Brazilian population is 60% of the total.
Although there are uncertainties with these numbers, they are based on a substantial amount of field experience and information, and thus should be treated as “estimated” and not “suspected”, allowing evaluation under Criterion C. Combining the different estimates (with the exception of the BirdLife estimate of 250-1000, which does indeed seem to fit the “suspected” category) would put the global population of this species in the range of 800-2000 mature individuals.
In terms of decline, this species suffers not only from habitat loss, but also other forms of persecution and mortality. Tree cover loss is not a good proxy for habitat loss in environments in which this species occurs, which include natural savannas, semi-arid areas and grasslands. Loss of natural grasslands in southern Brazil (Santa Catarina and Rio Grande do Sul) was estimated at 20% from 1985 to 2018 (ICMBio 2023). This is equivalent to a rate of decline of more than 10% over three generations, and if extrapolated to the rest of the range, together with the population estimate, would qualify the species as Vulnerable under criterion C1.
As mentioned in the account, electrocution is an important source of mortality in Argentina. Nine individuals were found electrocuted by power lines over an eight-year period in a study area in Argentina (Sarasola et al. 2020). Direct persecution, associated with the erroneous belief that this species is a predator of livestock, is also a major threat to this species, with 83 cases documented in Argentina over a 35-year period (Barbar et al. 2016). Drowning in artificial water reservoirs has also been documented in Argentina (see: https://www.rufford.org/projects/diego-gallego-garcia/rediscovering-and-protecting-chaco-eagle-populations-in-a-critical-area-for-its-conservation/ & https://whitleyaward.org/winners/the-chaco-eagle-a-flagship-for-semiarid-wildlife-conservation/). Only 30% of juveniles survive to adulthood, with equal numbers dying from being shot, electrocuted, or drowning in water tanks, and only 15% of deaths being from natural causes (J. H. Sarasola, personal communication, in ICMBio 2023).
In Brazil, direct persecution has also been documented, including an individual found shot and floating in a river in Tibagi, Paraná, in 2003 (skin deposited at the Capão da Imbuia Natural History Museum – MHNCI 5840). Others have been found dead or brought to rescue centres after suffering from direct persecution, including an adult individual that is now on display at the Curitiba Municipal Zoo. Five individuals were rescued in recent years with serious injuries as a result of collision with kite strings, in Minas Gerais, of which three survived. The practice of flying kites with strings coated with powdered glass (or other materials that can cut other kite strings) is illegal throughout Brazil. In 2012, an adult eagle was rescued in Jaguariaíva, Paraná, that had apparently been kept in poor conditions in captivity, and was suffering from malnutrition and muscular atrophy. Nest abandonment because of human activities, and the apparent killing of a fledgling by domestic dogs have also been reported (Zorzin et al. 2021).
Low breeding success in Brazil has been observed, with reproductive events by monitored pairs only every 2-3 years, and with only 33% of observed reprodutive attempts resulting in fledglings (Zorzin et al. 2021). The various forms of anthropogenic mortality are especially concerning as this species takes 4-6 years before reproducing for the first time, and produces at most one offspring during a successful breeding season (ICMBio 2023).
Taken together, and considering that this species exists as a single (sub)population, the estimate of a population of 800-2000 individuals, observations of elevated anthropogenic mortality, and low breeding success provide evidence for ongoing decline in this species, even though the rate of decline has not been quantified. We suggest that this species qualifies as Endangered under criterion C2a(ii).
References
Barbar, F., Capdevielle, A., Encabo, M., 2016. Direct Persecution of Crowned Eagles (Buteogallus coronatus) in Argentina: A New Call for Their Conservation. Journal of Raptor Research 50, 115–120. https://doi.org/10.3356/rapt-50-01-115-120.1
ICMBio, 2023. Relatório – Planejamento para Conservação da Águia-cinzenta (Buteogallus coronatus). 2023-2028. CEMAVE/ICMBio & PSN A Foundation, Curitiba, Brazil.
Marini, M.A.; Lima, D.M.; Carvalho, C.B.; Ubaid, F.K.; Silva, G.B.M.; Abreu, T.L.S.; Oliveira, T.D.; Alves, W.N.; Dias, F.F.; Alquezar, R.D. 2023. Urubitinga coronata (Vieillot, 1817). Sistema de Avaliação do Risco de Extinção da Biodiversidade – SALVE. Disponível em: https://salve.icmbio.gov.br DOI: 10.37002/salve.ficha.19738
Sarasola, J.H., Galmes, M.A., Watts, B.D., 2020. Electrocution on Power Lines is an Important Threat for the Endangered Chaco Eagle (Buteogallus coronatus) in Argentina. Journal of Raptor Research 54, 166–171. https://doi.org/10.3356/0892-1016-54.2.166
Scherer-Neto, P., et al. 2023. Monitoramento das aves de rapina diurnas na região do Parque Estadual Do Guartelá, Tibagi, Paraná 2014-2023. Instituto Água e Terra & PSN A Foundation.
Zorzin, G., de Carvalho-Filho, E.P.M., Armond, R.G., de Carvalho, G.D.M., 2021. Breeding biology and diet of the Chaco Eagle (Buteogallus coronatus) in southeast Brazil. Ornithol. Res. 29, 179–187. https://doi.org/10.1007/s43388-021-00074-x
Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested in commenting. The window for consultation is now closed and we are unable to accept any more comments until 12 February 2024. We will now analyse and interpret the information, and we will post a preliminary decision on this species’ Red List status on this page on 12 February 2024, when discussions will re-open.
We are grateful for the contributions made during this latest round of discussions, and all relevant information has been incorporated into the updated Red List assessment for this species. Based on the information provided by Ben Phalan, Pedro Scherer-Neto and Tony Bichinski, the global population size of this species can be estimated to fall in the range 800-2,000 mature individuals. Our preliminary proposal for the 2024 Red List would therefore be to list Crowned Solitary Eagle as Endangered under Criterion C2a(ii).
There is now a period for further comments until the final deadline on 18 February 2024, after which the recommended categorisations will be put forward to IUCN.
The final 2024 Red List categories will be published on the BirdLife and IUCN websites in December 2024, following further checking of information relevant to the assessments by both BirdLife and IUCN.
Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested in commenting. The window for consultation is now closed and we are unable to accept any more comments. We will analyse and interpret the information, and we will post a final decision on this species’ Red List status on this page on 26 February 2024.
Recommended categorisation to be put forward to IUCN
The final categorisation for this species has not changed. Crowned Solitary Eagle is recommended to be listed as Endangered under Criterion C2a(ii).
Many thanks for everyone who contributed to the 2024.1 GTB Forum process. The final 2024 Red List categories will now be published on the BirdLife and IUCN websites in October 2024, following further checking of information relevant to the assessments by both BirdLife and IUCN.
In Brazil, this species has long been associated with the Cerrado. In fact, this seems to be its main biome of occurrence, apart from the high altitude grasslands of Rio Grande do Sul. However, the species has been increasingly recorded in open areas of the Atlantic Forest biome, expressed in the numerous localities where it has been seen. Even though there are no more accurate censuses, my perception is that the species’ situation is not so serious as to be considered endangered.
In Paraguay the species is considered Vulnerable at the national level (in the most recent assessment, in 2017) due to a suspected ongoing decline of its small population. However, the population size has not been quantified, nor the rate of decline, though it is inferred to be significant due to the high rate of habitat loss (clearance and degradation of Chaco dry forest and Cerrado). There are no systematic studies of direct persecution or electrocution, though both seem likely to occur. The species’ stronghold in the country appear to be the westernmost Dry Chaco (Boqueron department) and northernmost Concepción department.
This species is known under various common and scientific names, which can make collating all relevant information more difficult: Crowned Solitary Eagle or Chaco Eagle in English, and águia-cinzenta in Portuguese. BirdLife treats as Buteogallus coronatus, while in Brazil it is classified as Urubitinga coronata, and it has also been referred to as Harpyhaliaetus coronatus.
This is a rare and threatened bird, and citizen science records may give a misleading impression of abundance, because individuals are very wide-ranging, even more so as juveniles and outside of the breeding season, so all records within a large area (for example, multiple municipalities in WikiAves or multiple locations in eBird), can refer to a single individual or pair. The home range of pairs or adults can be 500-600 kmˆ2, and juveniles can disperse over an area of 12,000 kmˆ2 during their dispersal period (Barbar et al. 2016, Marini et al. 2013). A recent workshop in Brazil brought together researchers on the species from across the species’ range, and the report can be provided (ICMBio 2023).
We can make some calculations based on one of the better-studied parts of this species’ range. In the state of Paraná, Brazil, the population is estimated, based on observations by experienced observers over the past decade, at 20-22 birds, including some that likely range into neighbouring states (Scherer-Neto et al. 2023, ICMBio 2023). As the state of Paraná makes up 2.5% of the species’ EOO (199,298 kmˆ2 out of 8,090,000 kmˆ2), a naive extrapolation of this population would give a total global population of 800-880 birds. We do not know if density in Paraná is representative of other parts of the range. We can make a conservative assumption that it is lower, as most of the western half of the state has been converted to soybeans, maize, pasture and other agricultural uses – however, it should be noted that this is also true of other large areas within this species’ range in the Cerrado, Chaco and Pampas. Even assuming that half of Paraná is entirely unsuitable, and as such that the density in the occupied part of the range is twice as high, extrapolation to the entire range would give an estimate of 1600-1760 birds, and this species would still qualify as Endangered under Criterion C. These calculations also do not allow for the fact that some individuals are immature, so the true number of mature individuals would be lower than this estimate of 800-1760 individuals.
These calculations are quite consistent with those of Marini et al. (2023), who present two estimates of the Brazilian population. One, based on the number of points of occurrence registered in Brazil (around 300), estimates 600-1000 mature individuals in Brazil. Brazil occupies approximately half of the global range of this species, so that would imply a global population of 1200-2000. Marini et al. account for the fact that some territories and individuals will not have been reported, but it is unclear if they account for the possibility that multiple points of occurrence across a wide area can refer to the same individual or pair, as mentioned above, and thus this could be an overestimate. Marini et al. also report an estimate of 150-600 mature individuals in Brazil, which is apparently derived from a previous BirdLife estimate of 250-1000 mature individuals globally, and an estimate that the Brazilian population is 60% of the total.
Although there are uncertainties with these numbers, they are based on a substantial amount of field experience and information, and thus should be treated as “estimated” and not “suspected”, allowing evaluation under Criterion C. Combining the different estimates (with the exception of the BirdLife estimate of 250-1000, which does indeed seem to fit the “suspected” category) would put the global population of this species in the range of 800-2000 mature individuals.
In terms of decline, this species suffers not only from habitat loss, but also other forms of persecution and mortality. Tree cover loss is not a good proxy for habitat loss in environments in which this species occurs, which include natural savannas, semi-arid areas and grasslands. Loss of natural grasslands in southern Brazil (Santa Catarina and Rio Grande do Sul) was estimated at 20% from 1985 to 2018 (ICMBio 2023). This is equivalent to a rate of decline of more than 10% over three generations, and if extrapolated to the rest of the range, together with the population estimate, would qualify the species as Vulnerable under criterion C1.
As mentioned in the account, electrocution is an important source of mortality in Argentina. Nine individuals were found electrocuted by power lines over an eight-year period in a study area in Argentina (Sarasola et al. 2020). Direct persecution, associated with the erroneous belief that this species is a predator of livestock, is also a major threat to this species, with 83 cases documented in Argentina over a 35-year period (Barbar et al. 2016). Drowning in artificial water reservoirs has also been documented in Argentina (see: https://www.rufford.org/projects/diego-gallego-garcia/rediscovering-and-protecting-chaco-eagle-populations-in-a-critical-area-for-its-conservation/ & https://whitleyaward.org/winners/the-chaco-eagle-a-flagship-for-semiarid-wildlife-conservation/). Only 30% of juveniles survive to adulthood, with equal numbers dying from being shot, electrocuted, or drowning in water tanks, and only 15% of deaths being from natural causes (J. H. Sarasola, personal communication, in ICMBio 2023).
In Brazil, direct persecution has also been documented, including an individual found shot and floating in a river in Tibagi, Paraná, in 2003 (skin deposited at the Capão da Imbuia Natural History Museum – MHNCI 5840). Others have been found dead or brought to rescue centres after suffering from direct persecution, including an adult individual that is now on display at the Curitiba Municipal Zoo. Five individuals were rescued in recent years with serious injuries as a result of collision with kite strings, in Minas Gerais, of which three survived. The practice of flying kites with strings coated with powdered glass (or other materials that can cut other kite strings) is illegal throughout Brazil. In 2012, an adult eagle was rescued in Jaguariaíva, Paraná, that had apparently been kept in poor conditions in captivity, and was suffering from malnutrition and muscular atrophy. Nest abandonment because of human activities, and the apparent killing of a fledgling by domestic dogs have also been reported (Zorzin et al. 2021).
Low breeding success in Brazil has been observed, with reproductive events by monitored pairs only every 2-3 years, and with only 33% of observed reprodutive attempts resulting in fledglings (Zorzin et al. 2021). The various forms of anthropogenic mortality are especially concerning as this species takes 4-6 years before reproducing for the first time, and produces at most one offspring during a successful breeding season (ICMBio 2023).
Taken together, and considering that this species exists as a single (sub)population, the estimate of a population of 800-2000 individuals, observations of elevated anthropogenic mortality, and low breeding success provide evidence for ongoing decline in this species, even though the rate of decline has not been quantified. We suggest that this species qualifies as Endangered under criterion C2a(ii).
References
Barbar, F., Capdevielle, A., Encabo, M., 2016. Direct Persecution of Crowned Eagles (Buteogallus coronatus) in Argentina: A New Call for Their Conservation. Journal of Raptor Research 50, 115–120. https://doi.org/10.3356/rapt-50-01-115-120.1
ICMBio, 2023. Relatório – Planejamento para Conservação da Águia-cinzenta (Buteogallus coronatus). 2023-2028. CEMAVE/ICMBio & PSN A Foundation, Curitiba, Brazil.
Marini, M.A.; Lima, D.M.; Carvalho, C.B.; Ubaid, F.K.; Silva, G.B.M.; Abreu, T.L.S.; Oliveira, T.D.; Alves, W.N.; Dias, F.F.; Alquezar, R.D. 2023. Urubitinga coronata (Vieillot, 1817). Sistema de Avaliação do Risco de Extinção da Biodiversidade – SALVE. Disponível em: https://salve.icmbio.gov.br DOI: 10.37002/salve.ficha.19738
Sarasola, J.H., Galmes, M.A., Watts, B.D., 2020. Electrocution on Power Lines is an Important Threat for the Endangered Chaco Eagle (Buteogallus coronatus) in Argentina. Journal of Raptor Research 54, 166–171. https://doi.org/10.3356/0892-1016-54.2.166
Scherer-Neto, P., et al. 2023. Monitoramento das aves de rapina diurnas na região do Parque Estadual Do Guartelá, Tibagi, Paraná 2014-2023. Instituto Água e Terra & PSN A Foundation.
Zorzin, G., de Carvalho-Filho, E.P.M., Armond, R.G., de Carvalho, G.D.M., 2021. Breeding biology and diet of the Chaco Eagle (Buteogallus coronatus) in southeast Brazil. Ornithol. Res. 29, 179–187. https://doi.org/10.1007/s43388-021-00074-x
Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested in commenting. The window for consultation is now closed and we are unable to accept any more comments until 12 February 2024. We will now analyse and interpret the information, and we will post a preliminary decision on this species’ Red List status on this page on 12 February 2024, when discussions will re-open.
Preliminary proposal
We are grateful for the contributions made during this latest round of discussions, and all relevant information has been incorporated into the updated Red List assessment for this species. Based on the information provided by Ben Phalan, Pedro Scherer-Neto and Tony Bichinski, the global population size of this species can be estimated to fall in the range 800-2,000 mature individuals. Our preliminary proposal for the 2024 Red List would therefore be to list Crowned Solitary Eagle as Endangered under Criterion C2a(ii).
There is now a period for further comments until the final deadline on 18 February 2024, after which the recommended categorisations will be put forward to IUCN.
The final 2024 Red List categories will be published on the BirdLife and IUCN websites in December 2024, following further checking of information relevant to the assessments by both BirdLife and IUCN.
Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested in commenting. The window for consultation is now closed and we are unable to accept any more comments. We will analyse and interpret the information, and we will post a final decision on this species’ Red List status on this page on 26 February 2024.
Recommended categorisation to be put forward to IUCN
The final categorisation for this species has not changed. Crowned Solitary Eagle is recommended to be listed as Endangered under Criterion C2a(ii).
Many thanks for everyone who contributed to the 2024.1 GTB Forum process. The final 2024 Red List categories will now be published on the BirdLife and IUCN websites in October 2024, following further checking of information relevant to the assessments by both BirdLife and IUCN.