6 thoughts on “Nicobar Sparrowhawk (Accipiter butleri)”
After a close perusal of the proposal, I realise the downlisting hinges only on three questions – that seems to be more subjective than other parameters.
1) Number of locations (B1a & B2a) – is it less than 10 (and what is the most plausible threat)
2) Number of sub-populations (C2aii) – is it 2 or 3-4.
2) Percentage of mature individuals in the largest subpopulation (C2aii) – is it 95% or more
Hence, assessments would definitely vary but I would list out my arguments to retain the existing criteria for Nicobar Sparrowhawk, which is probably the rarest resident raptor in India. https://birdcount.in/rarest-birds-of-india/
Nicobar Sparrowhawk has two subspecies – nominate that occurs in Car Nicobar Is. and obsoletus of Central Nicobar Islands. Despite many visits and surveys over the years, the species has never been reported from South Nicobar group of islands (largest area in Nicobar group) – hence, it must be treated as an endemic to Central and Car Nicobar group of islands. It is not quite clear entirely whether the EOO and AOO measures of BLI are in line with this distribution knowledge, but I think that does not really matter.
Status of the nominate subspecies: I am not aware of any recent definitive record of this subspecies from Car Nicobar Island. The island is believed to have undergone a dramatic transformation with coconut palm plantations replacing natural forests. I would caution against using satellite data for forest cover (Global Forest Watch) to estimate habitat decline, as they are likely to classify unsuitable habitats like plantations as forests. In all likelihood, this population might be really small and is on the verge of extinction.
Status of obsoletus subspecies: As already mentioned in the account, records are far and few between (see eBird, compare with EN-proposed Great Nicobar Serpent Eagle which is somewhat a similar forest raptor) and the terrain of Central Nicobar Islands (without mountains) render it susceptible to habitat degradation at a faster rate. There are no large protected-areas (of the size Great Nicobar Biosphere reserve) in these islands.
Criteria B
Area of Occupancy of 784 sq.km. seem a little higher (considering known island sizes Car Nicobar Is: 127, Katchal: 146, Kamorta: 131, Nancowry: 47) or even including potential ranges (Teresa:85, Tillangchong: 15, Trinket: 13, Bompuka: 10), and 2×2 grids over it. But I suspect it might just be over 500 sq. km. breaching the limit of Endangered, and hence may not matter.
Extend of Occurrence of 4,430 is already within the limits for Endangered (but captured as Vulnerable in the assessment sheet?). Hence, these are not really discussion topics.
The discussion points are on the sub-criteria of B. Continuing decline is already ‘Met’, as per the sheet – and I agree with it (just considering the state of Car Nicobar population).
However, I see no reason why the number of locations is not less than 10 – when the islands where it occurs is already mentioned. Even including other large islands, the number of locations is less than 10. A single development project in any of these islands can severely threaten the species – and Govt. of India is much interested in developing the islands of Nicobar and it would be the most plausible threat.
Criteria C
I see that the number of mature individuals is approaching 2,500. Looking at the current records, I find it hard to believe that its population is not below 2,500 for a forest raptor. Compare, with the population estimates of Great Nicobar Serpent Eagle (< 400 mature individuals) that occupy a much larger contiguous area.
Number of sub-populations: Typically, every subspecies of a species is a sub-population. I recommend that to be followed here, and hence there are only two sub-populations. The islands of Katchal, Nancowry and Kamorta are very close – the longest distance is between Katchal and Nancowry is 8km. I would say, this distance is not a deterrent for a one exchange every year for an Accipiter.
C2aii is met because it can be confidently stated, in the absence of records, that the Car Nicobar Is. do not even host 5% of the population and 95% of the birds are in Katchal-Kamorta-Nancowry.
Criteria D
It might be beneficial to redo the estimation to see whether the number of mature individuals will be less than 1,000 – again meeting Vulnerable (D1)
For specific queries.
Are there threats other than habitat loss that may be causing population declines?
– Not aware of any evidence
Are there data available to make a more accurate estimate of population size?
– Densities of a forest Accipiter may be multiplied by the island sizes. With a range below 450 sq. km., a bound of 2,500 mature individuals, would mean more than 5 mature individuals per sq. km – assuming uniformly suitable habitat. That seems unreasonable to me.
Is there evidence to suggest that the species occurs in other islands?
– It may be hypothesised that the species might occur in Teresa, Trinkut, Bompuka, and Tillanchong – that lies between Car Nicobar and Katchal/Kamorta. The likelihood of its occurrence in S. Nicobar Islands is rather low.
The Forest has reduced by 5% in those areas but the land use has changed a lot. Also hunting using airguns have increased a lot due to ease of availability which wasn’t there 16 years back. This are few comments based on the above discussion.
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 26 June 2023. We will now analyse and interpret the new information, and we will post a preliminary decision on this species’ Red List status on this page on 26 June 2023, when discussions will re-open.
We greatly appreciate and thank the contributions of Praveen J and Arun Singh in the above discussion, which have improved our understanding of this very poorly known species. To address the specific points raised:
We can confirm that the EOO and AOO have been calculated using the distribution outline above by Praveen J. We therefore believe them to be broadly correct. However, the AOO value given is a maximum. Accepting that this species is evidently rare and may not occupy all forest habitat across the island, a lower bound of 500km2 has been set for the AOO to incorporate this uncertainty. The EOO value does, indeed, meet the (initial) threshold for Endangered (‘Vulnerable’ is recorded in error).
We have updated the account to emphasise that the status of Car Nicobar taxon is wholly enigmatic and any population there must now be very small. It would be helpful to understand the amount of search effort that been undertaken on the island in reaching this conclusion.
Under Criterion B, difficulty is always presented in assessing the number of Locations, which is not simply the number of sites or islands a species occurs on, but rather reflects the spatial extent of acting threats. The decline of the species on Car Nicobar (or even possible extirpation) changes this equation, and while it remains very unlikely that the number of Locations remains very small (even if the species is now confined to Central Nicobars), it is evident that the species’ scarcity mean it is plausible that the number of Locations is less than 10.
Under Criterion C, the population data for Nicobar Sparrowhawk are too poor quality to produce a population estimate that satisfies the data thresholds of the IUCN Guidelines. The comment that the species proabbly numbers <2,500 mature individuals is noted, and this value has now been changed to be 500-2,500 (with acknowledgement that even this broad range has low reliability, but hopefully higher accuracy than previous estimates). But the absence of specific information means that this is only suspected and therefore does not meet the data thresholds for listing as Threatened under Criteria C or D.
Acknowledging all of the above, it is apparent that the previous proposal was overly evidentiary. A revised, more precautionary approach now suggests that the species should be listed as Vulnerable under Criteria B1ab(ii,iii,iv)+2ab(ii,iii,iv).
There is now a period for further comments until the final deadline on 2 July 2023, after which the recommended categorisations will be put forward to IUCN.
The final 2023 Red List categories will be published on the BirdLife and IUCN websites in December 2023, 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 10 July 2023.
Recommended categorisation to be put forward to IUCN
The final categorisation for this species has not changed. Nicobar Sparrowhawk is recommended to be listed as Vulnerable under Criteria B1ab(ii,iii,iv)+2ab(ii,iii,iv).
Many thanks for everyone who contributed to the 2023.2 GTB Forum process. The final 2023 Red List categories will be published on the BirdLife and IUCN websites in December 2023, following further checking of information relevant to the assessments by both BirdLife and IUCN.
After a close perusal of the proposal, I realise the downlisting hinges only on three questions – that seems to be more subjective than other parameters.
1) Number of locations (B1a & B2a) – is it less than 10 (and what is the most plausible threat)
2) Number of sub-populations (C2aii) – is it 2 or 3-4.
2) Percentage of mature individuals in the largest subpopulation (C2aii) – is it 95% or more
Hence, assessments would definitely vary but I would list out my arguments to retain the existing criteria for Nicobar Sparrowhawk, which is probably the rarest resident raptor in India.
https://birdcount.in/rarest-birds-of-india/
Nicobar Sparrowhawk has two subspecies – nominate that occurs in Car Nicobar Is. and obsoletus of Central Nicobar Islands. Despite many visits and surveys over the years, the species has never been reported from South Nicobar group of islands (largest area in Nicobar group) – hence, it must be treated as an endemic to Central and Car Nicobar group of islands. It is not quite clear entirely whether the EOO and AOO measures of BLI are in line with this distribution knowledge, but I think that does not really matter.
Status of the nominate subspecies: I am not aware of any recent definitive record of this subspecies from Car Nicobar Island. The island is believed to have undergone a dramatic transformation with coconut palm plantations replacing natural forests. I would caution against using satellite data for forest cover (Global Forest Watch) to estimate habitat decline, as they are likely to classify unsuitable habitats like plantations as forests. In all likelihood, this population might be really small and is on the verge of extinction.
Status of obsoletus subspecies: As already mentioned in the account, records are far and few between (see eBird, compare with EN-proposed Great Nicobar Serpent Eagle which is somewhat a similar forest raptor) and the terrain of Central Nicobar Islands (without mountains) render it susceptible to habitat degradation at a faster rate. There are no large protected-areas (of the size Great Nicobar Biosphere reserve) in these islands.
Criteria B
Area of Occupancy of 784 sq.km. seem a little higher (considering known island sizes Car Nicobar Is: 127, Katchal: 146, Kamorta: 131, Nancowry: 47) or even including potential ranges (Teresa:85, Tillangchong: 15, Trinket: 13, Bompuka: 10), and 2×2 grids over it. But I suspect it might just be over 500 sq. km. breaching the limit of Endangered, and hence may not matter.
Extend of Occurrence of 4,430 is already within the limits for Endangered (but captured as Vulnerable in the assessment sheet?). Hence, these are not really discussion topics.
The discussion points are on the sub-criteria of B. Continuing decline is already ‘Met’, as per the sheet – and I agree with it (just considering the state of Car Nicobar population).
However, I see no reason why the number of locations is not less than 10 – when the islands where it occurs is already mentioned. Even including other large islands, the number of locations is less than 10. A single development project in any of these islands can severely threaten the species – and Govt. of India is much interested in developing the islands of Nicobar and it would be the most plausible threat.
Criteria C
I see that the number of mature individuals is approaching 2,500. Looking at the current records, I find it hard to believe that its population is not below 2,500 for a forest raptor. Compare, with the population estimates of Great Nicobar Serpent Eagle (< 400 mature individuals) that occupy a much larger contiguous area.
Number of sub-populations: Typically, every subspecies of a species is a sub-population. I recommend that to be followed here, and hence there are only two sub-populations. The islands of Katchal, Nancowry and Kamorta are very close – the longest distance is between Katchal and Nancowry is 8km. I would say, this distance is not a deterrent for a one exchange every year for an Accipiter.
C2aii is met because it can be confidently stated, in the absence of records, that the Car Nicobar Is. do not even host 5% of the population and 95% of the birds are in Katchal-Kamorta-Nancowry.
Criteria D
It might be beneficial to redo the estimation to see whether the number of mature individuals will be less than 1,000 – again meeting Vulnerable (D1)
For specific queries.
Are there threats other than habitat loss that may be causing population declines?
– Not aware of any evidence
Are there data available to make a more accurate estimate of population size?
– Densities of a forest Accipiter may be multiplied by the island sizes. With a range below 450 sq. km., a bound of 2,500 mature individuals, would mean more than 5 mature individuals per sq. km – assuming uniformly suitable habitat. That seems unreasonable to me.
Is there evidence to suggest that the species occurs in other islands?
– It may be hypothesised that the species might occur in Teresa, Trinkut, Bompuka, and Tillanchong – that lies between Car Nicobar and Katchal/Kamorta. The likelihood of its occurrence in S. Nicobar Islands is rather low.
The Forest has reduced by 5% in those areas but the land use has changed a lot. Also hunting using airguns have increased a lot due to ease of availability which wasn’t there 16 years back. This are few comments based on the above discussion.
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 26 June 2023. We will now analyse and interpret the new information, and we will post a preliminary decision on this species’ Red List status on this page on 26 June 2023, when discussions will re-open.
Preliminary proposal
We greatly appreciate and thank the contributions of Praveen J and Arun Singh in the above discussion, which have improved our understanding of this very poorly known species. To address the specific points raised:
We can confirm that the EOO and AOO have been calculated using the distribution outline above by Praveen J. We therefore believe them to be broadly correct. However, the AOO value given is a maximum. Accepting that this species is evidently rare and may not occupy all forest habitat across the island, a lower bound of 500km2 has been set for the AOO to incorporate this uncertainty. The EOO value does, indeed, meet the (initial) threshold for Endangered (‘Vulnerable’ is recorded in error).
We have updated the account to emphasise that the status of Car Nicobar taxon is wholly enigmatic and any population there must now be very small. It would be helpful to understand the amount of search effort that been undertaken on the island in reaching this conclusion.
Under Criterion B, difficulty is always presented in assessing the number of Locations, which is not simply the number of sites or islands a species occurs on, but rather reflects the spatial extent of acting threats. The decline of the species on Car Nicobar (or even possible extirpation) changes this equation, and while it remains very unlikely that the number of Locations remains very small (even if the species is now confined to Central Nicobars), it is evident that the species’ scarcity mean it is plausible that the number of Locations is less than 10.
Under Criterion C, the population data for Nicobar Sparrowhawk are too poor quality to produce a population estimate that satisfies the data thresholds of the IUCN Guidelines. The comment that the species proabbly numbers <2,500 mature individuals is noted, and this value has now been changed to be 500-2,500 (with acknowledgement that even this broad range has low reliability, but hopefully higher accuracy than previous estimates). But the absence of specific information means that this is only suspected and therefore does not meet the data thresholds for listing as Threatened under Criteria C or D.
Acknowledging all of the above, it is apparent that the previous proposal was overly evidentiary. A revised, more precautionary approach now suggests that the species should be listed as Vulnerable under Criteria B1ab(ii,iii,iv)+2ab(ii,iii,iv).
There is now a period for further comments until the final deadline on 2 July 2023, after which the recommended categorisations will be put forward to IUCN.
The final 2023 Red List categories will be published on the BirdLife and IUCN websites in December 2023, 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 10 July 2023.
Recommended categorisation to be put forward to IUCN
The final categorisation for this species has not changed. Nicobar Sparrowhawk is recommended to be listed as Vulnerable under Criteria B1ab(ii,iii,iv)+2ab(ii,iii,iv).
Many thanks for everyone who contributed to the 2023.2 GTB Forum process. The final 2023 Red List categories will be published on the BirdLife and IUCN websites in December 2023, following further checking of information relevant to the assessments by both BirdLife and IUCN.