6 thoughts on “White-browed Reed-warbler (Acrocephalus tangorum)”
I disagree with the downlisting. As mentioned in the justification note, habitat loss and illegal mist-netting continue to pose significant threats to the species at its wintering sites. Although it was concluded that the population may be larger than current data suggest—given the species’ wide wintering range, much of which remains unsurveyed—there is still no confirmed evidence that the species’ status is improving.
In our recent study in the Central Plains of Thailand where this species is a regular winter visitor to the lower part, 98% of detections occur outside the protected area network (Angkaew et al., 2023). These remaining habitats are disappearing rapidly due to urban expansion and land conversion. We found that the species is largely confined to extensive 𝘈𝘤𝘵𝘪𝘯𝘰𝘴𝘤𝘪𝘳𝘱𝘶𝘴 𝘨𝘳𝘰𝘴𝘴𝘶𝘴 or 𝘗𝘩𝘳𝘢𝘨𝘮𝘪𝘵𝘦𝘴 reedbeds in open habitats. These natural reedbeds have been increasingly replaced by the non-native 𝘛𝘺𝘱𝘩𝘢 reeds and Mimosoid shrubs unsuitable for this species, indicating that the amount of suitable wintering habitat may be even more limited than previously thought.
Not only that its wintering habitats are largely unprotected by law, birds inhabiting these habitats have become more at risk of habitat loss due to the Land and Building Tax Act B.E. 2562 (2019), which imposes higher tax rates on “unused or abandoned” lands. As a result, many landowners have been converting areas supporting natural reedbeds into residential developments or agricultural land (e.g., monoculture plantations and orchards) to avoid the higher tax burden. This policy-driven pressure has further accelerated habitat conversion, putting additional pressure on the remaining suitable habitats for this species.
Our findings in Thailand reveal that the species’ habitat is highly fragmented and subject to a high rate of loss, which raises serious concerns for its long-term survival.
Angkaew, R., D. Ngoprasert, L. A. Powell, W. Limparungpatthanakij, P. D. Round, and G. A. Gale. 2023. Variation in avian responses to rice intensification in the central plains of Thailand guides conservation opportunities. Biological Conservation 286, https://doi.org/10.1016/j.biocon.2023.110307
The rate of habitat loss in the wintering grounds in Thailand has been accelerated by the land-use changes, recently resulted largely from the current legislation that imposes higher tax rates on “unused lands” that support natural reedbeds this species depend upon. Many sites I recorded this species just a few years ago have now been converted and are no longer suitable. I think that it should remain on the list of threatened species.
On another note, Blunt-winged Warbler is another species similarly affected by habitat loss in the wintering grounds here.
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 information provided in the above comments. Information on threats will be into the updated species factsheet. Based on the provided information, our preliminary proposal for the 2025 Red List would be to list White-browed Reed-warbler as Vulnerable under Criteria A3c+4c.
The initial assessment recognised that the species is declining, but the limited information on habitat loss was deemed insufficient to determine the rate of decline required for an assessment under Criterion A. However, R. Angkaew and W. Limparungpatthanakij have highlighted that land-use change is increasing because of changing legislation in Thailand, where a significant majority of the global population may plausibly winter. Furthermore, Angkaew et al. (2023) found that most of the Thai population occurs outside protected areas. On the basis that this species plausibly has a small to moderately small population size, even small-scale land-use change has the potential to cause a rapid reduction in the population size. Given significant ongoing changes in land-use in Thailand (J. Eaton in litt.), and the conversion of grasslands and scrub into cropland, it is possible that over the next 10 years the species will decline rapidly. Precautionarily, a decline of 10-40% is suspected, and the species is proposed to be maintained as VU A3c+4c. This is a precautionary assessment that incorporates a worst-case scenario (i.e. that land-use change in Thailand will be rapid, and that the majority of the global population is in Thailand), along with a more optimistic scenario that neither of these assumptions may prove to be true. As evidence that this precautionary approach is warranted, Kao Sam Roi (a significant wintering site for the species) is apparently subject to ongoing destruction (J. Eaton in litt.).
Additionally, we would like to kindly request further information to support this listing. Specifically, information on the percentage of habitat lost or likely to be lost over ten years, or the percentage of habitat currently under private ownership (and thus at potential risk of being cleared) within the species’ wintering range would be beneficial.
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.
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. White-browed Reed-warbler is recommended to be listed as Vulnerable under Criteria A3c+4c.
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.
I disagree with the downlisting. As mentioned in the justification note, habitat loss and illegal mist-netting continue to pose significant threats to the species at its wintering sites. Although it was concluded that the population may be larger than current data suggest—given the species’ wide wintering range, much of which remains unsurveyed—there is still no confirmed evidence that the species’ status is improving.
In our recent study in the Central Plains of Thailand where this species is a regular winter visitor to the lower part, 98% of detections occur outside the protected area network (Angkaew et al., 2023). These remaining habitats are disappearing rapidly due to urban expansion and land conversion. We found that the species is largely confined to extensive 𝘈𝘤𝘵𝘪𝘯𝘰𝘴𝘤𝘪𝘳𝘱𝘶𝘴 𝘨𝘳𝘰𝘴𝘴𝘶𝘴 or 𝘗𝘩𝘳𝘢𝘨𝘮𝘪𝘵𝘦𝘴 reedbeds in open habitats. These natural reedbeds have been increasingly replaced by the non-native 𝘛𝘺𝘱𝘩𝘢 reeds and Mimosoid shrubs unsuitable for this species, indicating that the amount of suitable wintering habitat may be even more limited than previously thought.
Not only that its wintering habitats are largely unprotected by law, birds inhabiting these habitats have become more at risk of habitat loss due to the Land and Building Tax Act B.E. 2562 (2019), which imposes higher tax rates on “unused or abandoned” lands. As a result, many landowners have been converting areas supporting natural reedbeds into residential developments or agricultural land (e.g., monoculture plantations and orchards) to avoid the higher tax burden. This policy-driven pressure has further accelerated habitat conversion, putting additional pressure on the remaining suitable habitats for this species.
Our findings in Thailand reveal that the species’ habitat is highly fragmented and subject to a high rate of loss, which raises serious concerns for its long-term survival.
Angkaew, R., D. Ngoprasert, L. A. Powell, W. Limparungpatthanakij, P. D. Round, and G. A. Gale. 2023. Variation in avian responses to rice intensification in the central plains of Thailand guides conservation opportunities. Biological Conservation 286, https://doi.org/10.1016/j.biocon.2023.110307
The rate of habitat loss in the wintering grounds in Thailand has been accelerated by the land-use changes, recently resulted largely from the current legislation that imposes higher tax rates on “unused lands” that support natural reedbeds this species depend upon. Many sites I recorded this species just a few years ago have now been converted and are no longer suitable. I think that it should remain on the list of threatened species.
On another note, Blunt-winged Warbler is another species similarly affected by habitat loss in the wintering grounds here.
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 information provided in the above comments. Information on threats will be into the updated species factsheet. Based on the provided information, our preliminary proposal for the 2025 Red List would be to list White-browed Reed-warbler as Vulnerable under Criteria A3c+4c.
The initial assessment recognised that the species is declining, but the limited information on habitat loss was deemed insufficient to determine the rate of decline required for an assessment under Criterion A. However, R. Angkaew and W. Limparungpatthanakij have highlighted that land-use change is increasing because of changing legislation in Thailand, where a significant majority of the global population may plausibly winter. Furthermore, Angkaew et al. (2023) found that most of the Thai population occurs outside protected areas. On the basis that this species plausibly has a small to moderately small population size, even small-scale land-use change has the potential to cause a rapid reduction in the population size. Given significant ongoing changes in land-use in Thailand (J. Eaton in litt.), and the conversion of grasslands and scrub into cropland, it is possible that over the next 10 years the species will decline rapidly. Precautionarily, a decline of 10-40% is suspected, and the species is proposed to be maintained as VU A3c+4c. This is a precautionary assessment that incorporates a worst-case scenario (i.e. that land-use change in Thailand will be rapid, and that the majority of the global population is in Thailand), along with a more optimistic scenario that neither of these assumptions may prove to be true. As evidence that this precautionary approach is warranted, Kao Sam Roi (a significant wintering site for the species) is apparently subject to ongoing destruction (J. Eaton in litt.).
Additionally, we would like to kindly request further information to support this listing. Specifically, information on the percentage of habitat lost or likely to be lost over ten years, or the percentage of habitat currently under private ownership (and thus at potential risk of being cleared) within the species’ wintering range would be beneficial.
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.
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. White-browed Reed-warbler is recommended to be listed as Vulnerable under Criteria A3c+4c.
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.