9 thoughts on “Strange-tailed Tyrant (Alectrurus risora)”
This species has been neglected in assessments of endangered species in Brazil. However, given the specific habitat of the species, its conservation status in Brazil is a cause for concern, considering the rate of conversion of native grasslands into cultivated exotic pastures, especially in the Pantanal and surrounding areas.
The past scenario for this species has been extremely adverse (a 90% loss of its historical EOO), and the current NT category does not reflect its current status, nor that of the next 10 years, due to continued habitat loss. We have long believed that this species might qualify as EN rather than VU. We were “surprised” by this poorly justified document proposing its classification as NT. The species should retain its global VU status until a new comprehensive global assessment involving local experts is conducted.
Based on information from our research group, which has been investigating the biology of this species for several years, here is a review of the criteria that we have quickly developed to contribute to this discussion:
Criterion A.
POPULATION DECLINE RATE: >30% over three generations (Vulnerable, VU)
Evidence: Data on longevity from over 100 banded individuals monitored throughout their lifespans indicate that they can live up to 10 years. Thus, an average of 20–25 years could be used to estimate three generations. The population in northeastern Corrientes declined by 80% between 2002 and 2019, according to an unpublished study. In Argentina’s IBAs, where all subpopulations and occupied sites were identified, population sizes were estimated in 2008. A recent rapid assessment of the current status of these populations shows at least a 35% decline. In Paraguay’s IBAs identified in 2007, there are currently only sparse records from 7 out of 10 sites. Moreover, grassland loss and degradation in northeastern Argentina exceed 30%, considering agricultural expansion, afforestation, recurrence of mega-fires and livestock intensification (the species does not breed successfully in recently burned and grazed fields). In summary, the species’ occupancy in IBAs and habitat loss suggest that the population decline rate can be estimated as greater than or equal to 30%.
________________________________________
Criterion B.
AOO: <2000 km² (Vulnerable, VU)
Evidence: The species’ subpopulations or occupied areas are highly fragmented and generally small in size due to the species’ breeding site selection, which is highly sensitive to livestock grazing. We performed a rapid AOO estimate using presence records provided by experts. For example, in the largest and most continuous population located in Iberá National Park, the grassland area inhabited by the species represents less than 10% of the ecosystem, with a maximum extent of about 750 km². Other small, stable populations occur in protected areas, each occupying between 30 and 50 km². Populations in livestock areas outside protected zones are even smaller, more fluctuating, and occupy less area. Overall, the AOO is estimated to be below 2,000 km².
________________________________________
Criterion C.
POPULATION SIZE: <10,000 individuals (Vulnerable, VU or Endangered, EN)
Evidence: Population size estimates for the species’ known locations were provided by experts. These are conservative estimates and do not account for population fluctuations caused by grassland mega-fires during the breeding seasons in northeastern Argentina and eastern Paraguay. In Argentina, the current population in main IBAs and KBAs is estimated at 2,900 individuals. In Paraguay’s IBAs, the reported numbers are very low, and some sites lack current records. Populations outside IBAs are expected to be even smaller and more fluctuating. Therefore, the total number of mature individuals does not approach 10,000; in fact, our current estimate is closer to 5,000.
________________________________________
NATIONAL CONSERVATION STATUS OF THE SPECIES (Endangered, EN)
It is important to highlight that in the 2015 national Red List assessment of threatened birds in Argentina, conducted by the ornithological community using IUCN methodology, the species was classified as EN (Endangered). Given that the main populations are located in Argentina, the appropriate action would be to reassess the species for an uplisting from VU to EN, rather than a downlisting from VU to NT.
Contributors: Alejandro Di Giacomo (AVES ARGENTINAS), Melanie Browne (CONICET), Juan Francisco Cataudela (CONICET), Cecilia Kopuchian (CONICET & AVES ARGENTINAS), Simon Kraemer (CONICET), Florencia Pucheta (CONICET & AVES ARGENTINAS), Jonas Rosoni (CONICET), Adrian Di Giacomo (CONICET & AVES ARGENTINAS).
As Coordinator of the Grasslands Program of Aves Argentinas (a BirdLife International partner), I do not support the category change of the Strange-tailed Tyrant. Most of the global population occurs in Argentina, where, in addition, the species has been studied over the last 20 years by top scientists working in conservation biology. Most of their studies show that the species has been declining and losing territory as forestation, crops and conventional forms of livestock farming have advanced.
In Paraguay the species was considered as Endangered in the most recent national Red List assessment (2017) due to ongoing loss of its wet grassland habitat. Although widespread in the southwestern part of the country, the species is extremely localized. Although there appears to be some movement of individuals, suitable habitat is now highly fragmented. Since the last national assessment there has been a dramatic increase in afforestation and conversion of wet grasslands to rice plantations, affecting at least two main areas for the species in the country. Furthermore, a very significant proportion of all grasslands in Paraguay burn each year. At least two populations are also at risk of direct mortality from cars (either flying across roads or from foraging on roads). While quantitative data are not currently available regarding the population and threats in the country, a qualitative assessment would suggest the species’ status might warrant uplisting to EN rather than downlisting to NT.
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 25 April 2025. We will now analyse and interpret the information, and we will post a preliminary decision on this species’ Red List category on this page on 25 April 2025, when discussions will re-open.
We thank all contributors for the information provided in the above comments and via email. All relevant information will be incorporated into the updated species factsheet.
Based on available information, our preliminary proposal for the 2025 Red List would be to list
Strange-tailed Tyrant as Vulnerable under Criterion C2a(ii). This is based on a revised population estimate of 3,000-10,000 mature individuals.
We thank A.S. Di Giacomo and their colleagues for their detailed assessment of this species. We would like to respond specifically to each criteria discussed and ask for further information which can further support this assessment.
Criterion A: BirdLife follows the methodology by Bird et al. (2020) for calculating generation lengths. Using this method, a generation length of 2.84 years is determined for this species. This indicates that reductions should be calculated over a period of ten years as per the IUCN Guidelines. Regardless, the numbers reported for northeastern Corrientes are alarming and indicate declines exceeding 30% over ten years. We kindly ask whether the unpublished report referenced for the 80% declines can be made available to us, or whether the underlying data and calculations be made available? This information would allow us to also list the species as Vulnerable under Criterion A.
Criterion B: BirdLife calculates the AOO by placing a 2×2 km grid over the extent of suitable habitat as opposed to presence records. This method indicates an AOO that is >2,000 km2. Therefore, we determine that the species does not meet the thresholds for Vulnerable under Criterion B.
Criterion C: We agree with the assessment of this species under Criterion C, and it will be retained as VU under this Criterion. As outlined in a separately provided email, the previously reported population estimate of 23,000 for Ibera National Park is unreliable, and we are pleased to receive an updated population estimate. We would also like to request further information regarding the Argentinian population estimate. Specifically, is it possible that the data and methods for calculating this estimate be made available? This would further support justification for retaining the species as VU. We propose that the population size be put in the wider band of 3,000-10,000 mature individuals to capture the uncertainty, but if more information can be provided, this estimate may be revised down.
Additionally, we would also like to address suggestions that the species be considered for uplisting to Endangered. For this change to be considered, considerable evidence (including underlying data and methods) should be provided that demonstrates that there are either less than 2,500 mature individuals globally, or that a population reduction over ten years exceeding 50% has occurred. According to the information provided, this does not seem to be the case. However, if this information can be provided either during this forum, or sometime in the future, the species can be reassessed.
We would also like to thank R. Clay for his comment regarding the status and threats of the species in Paraguay. This information will be included to support the assessment. If there is any additional information regarding the population size, rate of decline, and the methods for determining the species’ EN status in Paraguay, that would be hugely beneficial for the assessment.
There is now a period for further comments until the final deadline on 4 May 2025, after which the recommended categorisations will be put forward to IUCN.
The final 2025 Red List categories will be published on the BirdLife and IUCN websites in October 2025, following further checking of information relevant to the assessments by both BirdLife and IUCN.
References:
Bird, J.P., Martin, R., Akçakaya, H.R., Gilroy, J., Burfield, I.J., Garnett, S.T., Symes, A., Taylor, J., Şekercioğlu, Ç.H. and Butchart, S.H. (2020). Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology, 34(5), pp.1252-1261.
The species was listed in EN in the most recent national Red List Assessment for Paraguay under C1, based on experience of observers familiar with the habitats and locations of the species in the country. (I’ll try to get some quantitative data on grassland loss and burns prior to the deadline).
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 a final decision on this species’ Red List category will be posted on this page on 12 May 2025.
Recommended categorisation to be put forward to IUCN
The final categorisation for this species has not changed. Strange-tailed Tyrant is recommended to be listed as Vulnerable under Criterion C2a(ii).
We would like to thank R. Clay for their comment. Additional quantitative data would be welcomed. The final categorisation cannot be changed beyond the May 12th deadline, but additional information can still be incorporated where appropriate into the updated species factsheets beyond this date. We will gladly accept additional information at redlistteam@birdlife.org.
Many thanks for everyone who contributed to the 2025.2 GTB Forum process. The final Red List categories will be published on the BirdLife and IUCN websites in October 2025, following further checking of information relevant to the assessments by both BirdLife and IUCN.
This species has been neglected in assessments of endangered species in Brazil. However, given the specific habitat of the species, its conservation status in Brazil is a cause for concern, considering the rate of conversion of native grasslands into cultivated exotic pastures, especially in the Pantanal and surrounding areas.
The past scenario for this species has been extremely adverse (a 90% loss of its historical EOO), and the current NT category does not reflect its current status, nor that of the next 10 years, due to continued habitat loss. We have long believed that this species might qualify as EN rather than VU. We were “surprised” by this poorly justified document proposing its classification as NT. The species should retain its global VU status until a new comprehensive global assessment involving local experts is conducted.
Based on information from our research group, which has been investigating the biology of this species for several years, here is a review of the criteria that we have quickly developed to contribute to this discussion:
Criterion A.
POPULATION DECLINE RATE: >30% over three generations (Vulnerable, VU)
Evidence: Data on longevity from over 100 banded individuals monitored throughout their lifespans indicate that they can live up to 10 years. Thus, an average of 20–25 years could be used to estimate three generations. The population in northeastern Corrientes declined by 80% between 2002 and 2019, according to an unpublished study. In Argentina’s IBAs, where all subpopulations and occupied sites were identified, population sizes were estimated in 2008. A recent rapid assessment of the current status of these populations shows at least a 35% decline. In Paraguay’s IBAs identified in 2007, there are currently only sparse records from 7 out of 10 sites. Moreover, grassland loss and degradation in northeastern Argentina exceed 30%, considering agricultural expansion, afforestation, recurrence of mega-fires and livestock intensification (the species does not breed successfully in recently burned and grazed fields). In summary, the species’ occupancy in IBAs and habitat loss suggest that the population decline rate can be estimated as greater than or equal to 30%.
________________________________________
Criterion B.
AOO: <2000 km² (Vulnerable, VU)
Evidence: The species’ subpopulations or occupied areas are highly fragmented and generally small in size due to the species’ breeding site selection, which is highly sensitive to livestock grazing. We performed a rapid AOO estimate using presence records provided by experts. For example, in the largest and most continuous population located in Iberá National Park, the grassland area inhabited by the species represents less than 10% of the ecosystem, with a maximum extent of about 750 km². Other small, stable populations occur in protected areas, each occupying between 30 and 50 km². Populations in livestock areas outside protected zones are even smaller, more fluctuating, and occupy less area. Overall, the AOO is estimated to be below 2,000 km².
________________________________________
Criterion C.
POPULATION SIZE: <10,000 individuals (Vulnerable, VU or Endangered, EN)
Evidence: Population size estimates for the species’ known locations were provided by experts. These are conservative estimates and do not account for population fluctuations caused by grassland mega-fires during the breeding seasons in northeastern Argentina and eastern Paraguay. In Argentina, the current population in main IBAs and KBAs is estimated at 2,900 individuals. In Paraguay’s IBAs, the reported numbers are very low, and some sites lack current records. Populations outside IBAs are expected to be even smaller and more fluctuating. Therefore, the total number of mature individuals does not approach 10,000; in fact, our current estimate is closer to 5,000.
________________________________________
NATIONAL CONSERVATION STATUS OF THE SPECIES (Endangered, EN)
It is important to highlight that in the 2015 national Red List assessment of threatened birds in Argentina, conducted by the ornithological community using IUCN methodology, the species was classified as EN (Endangered). Given that the main populations are located in Argentina, the appropriate action would be to reassess the species for an uplisting from VU to EN, rather than a downlisting from VU to NT.
Contributors: Alejandro Di Giacomo (AVES ARGENTINAS), Melanie Browne (CONICET), Juan Francisco Cataudela (CONICET), Cecilia Kopuchian (CONICET & AVES ARGENTINAS), Simon Kraemer (CONICET), Florencia Pucheta (CONICET & AVES ARGENTINAS), Jonas Rosoni (CONICET), Adrian Di Giacomo (CONICET & AVES ARGENTINAS).
As Coordinator of the Grasslands Program of Aves Argentinas (a BirdLife International partner), I do not support the category change of the Strange-tailed Tyrant. Most of the global population occurs in Argentina, where, in addition, the species has been studied over the last 20 years by top scientists working in conservation biology. Most of their studies show that the species has been declining and losing territory as forestation, crops and conventional forms of livestock farming have advanced.
In Paraguay the species was considered as Endangered in the most recent national Red List assessment (2017) due to ongoing loss of its wet grassland habitat. Although widespread in the southwestern part of the country, the species is extremely localized. Although there appears to be some movement of individuals, suitable habitat is now highly fragmented. Since the last national assessment there has been a dramatic increase in afforestation and conversion of wet grasslands to rice plantations, affecting at least two main areas for the species in the country. Furthermore, a very significant proportion of all grasslands in Paraguay burn each year. At least two populations are also at risk of direct mortality from cars (either flying across roads or from foraging on roads). While quantitative data are not currently available regarding the population and threats in the country, a qualitative assessment would suggest the species’ status might warrant uplisting to EN rather than downlisting to NT.
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 25 April 2025. We will now analyse and interpret the information, and we will post a preliminary decision on this species’ Red List category on this page on 25 April 2025, when discussions will re-open.
Preliminary proposal
We thank all contributors for the information provided in the above comments and via email. All relevant information will be incorporated into the updated species factsheet.
Based on available information, our preliminary proposal for the 2025 Red List would be to list
Strange-tailed Tyrant as Vulnerable under Criterion C2a(ii). This is based on a revised population estimate of 3,000-10,000 mature individuals.
We thank A.S. Di Giacomo and their colleagues for their detailed assessment of this species. We would like to respond specifically to each criteria discussed and ask for further information which can further support this assessment.
Criterion A: BirdLife follows the methodology by Bird et al. (2020) for calculating generation lengths. Using this method, a generation length of 2.84 years is determined for this species. This indicates that reductions should be calculated over a period of ten years as per the IUCN Guidelines. Regardless, the numbers reported for northeastern Corrientes are alarming and indicate declines exceeding 30% over ten years. We kindly ask whether the unpublished report referenced for the 80% declines can be made available to us, or whether the underlying data and calculations be made available? This information would allow us to also list the species as Vulnerable under Criterion A.
Criterion B: BirdLife calculates the AOO by placing a 2×2 km grid over the extent of suitable habitat as opposed to presence records. This method indicates an AOO that is >2,000 km2. Therefore, we determine that the species does not meet the thresholds for Vulnerable under Criterion B.
Criterion C: We agree with the assessment of this species under Criterion C, and it will be retained as VU under this Criterion. As outlined in a separately provided email, the previously reported population estimate of 23,000 for Ibera National Park is unreliable, and we are pleased to receive an updated population estimate. We would also like to request further information regarding the Argentinian population estimate. Specifically, is it possible that the data and methods for calculating this estimate be made available? This would further support justification for retaining the species as VU. We propose that the population size be put in the wider band of 3,000-10,000 mature individuals to capture the uncertainty, but if more information can be provided, this estimate may be revised down.
Additionally, we would also like to address suggestions that the species be considered for uplisting to Endangered. For this change to be considered, considerable evidence (including underlying data and methods) should be provided that demonstrates that there are either less than 2,500 mature individuals globally, or that a population reduction over ten years exceeding 50% has occurred. According to the information provided, this does not seem to be the case. However, if this information can be provided either during this forum, or sometime in the future, the species can be reassessed.
We would also like to thank R. Clay for his comment regarding the status and threats of the species in Paraguay. This information will be included to support the assessment. If there is any additional information regarding the population size, rate of decline, and the methods for determining the species’ EN status in Paraguay, that would be hugely beneficial for the assessment.
There is now a period for further comments until the final deadline on 4 May 2025, after which the recommended categorisations will be put forward to IUCN.
The final 2025 Red List categories will be published on the BirdLife and IUCN websites in October 2025, following further checking of information relevant to the assessments by both BirdLife and IUCN.
References:
Bird, J.P., Martin, R., Akçakaya, H.R., Gilroy, J., Burfield, I.J., Garnett, S.T., Symes, A., Taylor, J., Şekercioğlu, Ç.H. and Butchart, S.H. (2020). Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology, 34(5), pp.1252-1261.
The species was listed in EN in the most recent national Red List Assessment for Paraguay under C1, based on experience of observers familiar with the habitats and locations of the species in the country. (I’ll try to get some quantitative data on grassland loss and burns prior to the deadline).
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 a final decision on this species’ Red List category will be posted on this page on 12 May 2025.
Recommended categorisation to be put forward to IUCN
The final categorisation for this species has not changed. Strange-tailed Tyrant is recommended to be listed as Vulnerable under Criterion C2a(ii).
We would like to thank R. Clay for their comment. Additional quantitative data would be welcomed. The final categorisation cannot be changed beyond the May 12th deadline, but additional information can still be incorporated where appropriate into the updated species factsheets beyond this date. We will gladly accept additional information at redlistteam@birdlife.org.
Many thanks for everyone who contributed to the 2025.2 GTB Forum process. The final Red List categories will be published on the BirdLife and IUCN websites in October 2025, following further checking of information relevant to the assessments by both BirdLife and IUCN.