6 thoughts on “Eastern Bristlebird (Dasyornis brachypterus): Revise global status?”
We have recently received information via email (D. Bain in litt.) that a 78% decline at Barren Gounds/Budderoo and an 81% decline at Nadgee has been estimated following recent fires. These data were not accounted for in the species account in APAB. This information is currently being considered by the Red List Team to determine whether it alters the proposal herein.
This new information has important implications for the status of the Eastern Bristlebird. The Barren Grounds/Budderoo subpopulation was one of the largest so a decline of 78% in the last three generations (11 years) from unknown causes (since the area was not burnt), combined with losses from Nadgee/Howe Flat from the 2020 fires, unfortunately would appear to return the species to the status of Vulnerable depending on the population size of Beecroft peninsula.
Historical population data do make things confusing but here is a potted summary based on action plans.
In the 2010 Action Plan the population was estimated at 2550 individuals overall but the maximum totals for the subpopulations was there were estimated to be 1250 at Barren Grounds/Budderoo, 1100 at Jervis Bay (including Bherwerre and Beecroft Peninsulas, birds having been introduced to the latter in 2003-5), 50 at Cataract, 10 at Red Rocks, 300 at Nadgee & Howe Flat, and 31 in the north – a total of 2760.
By 2018 the estimate was raised to 2835 in the Threatened Species Commissioners interim report
In the 2020 Action Plan that forms the basis of the account given here, the total is 3000 which includes many of exactly the same figures from 2010 – 1250 at Barren Grounds/Budderoo, 1100 at Jervis Bay (but noting that the population on Beecroft Peninsula is unknown and densities there were high), 50 at Cataract, 10 at Red Rocks, 350 at Nadgee (it was as high as 400 before the fires but mortality of up to 11% was estimated) and 150 at Howe Flat, and 31 in the north – a total of 2941.
Given the declines reported by David Bain, the losses of nearly 1000 birds from Barren Grounds/Budderoo represent a loss of 32% had there been no losses at Nadgee, though would be below if the population on Beecroft Peninsula is >250 higher than estimated. Such losses are dramatic given that Budderoo had the highest density ever recorded in 2019. Given losses of over 300 birds from Nadgee, the total decline since 2019 could be as high as 43%, or 39% since 2010. The losses would still exceed 30% since 2019 unless the Beecroft Peninsula was >1400 birds additional to those counted (or >900 for 2010 estimates).
There is thus a strong argument that the Eastern Bristlebird be listed as VU: A2bc, especially as there have been no recent surveys at many locations from which population estimates have been made, so considerable uncertainty.
I think there is insufficient evidence to say this rate of loss is continuing (Criterion A4) or operate over the next 3 generations (A3).
I also think that recent evidence does not support listing under Criterion B. The survival of birds at Nadgee, despite a ferocious fire, and evidence of Western Bristlebirds escaping to the unburnt fringes of habitat and remaining there until their heaths recover (Mcnee et al. 2021), make it likely that many of the populations live in multiple locations with respect to the threat of fire, and no other threat is permanently removing their habitat.
McNee, S., Newbey, B., Comer, S. and Burbidge, A.H., 2021. Western Bristlebird Dasyornis longirostris: Response to fire and persistence of home range in the Fitzgerald River National Park, Western Australia. Australian Field Ornithology, 38.
Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested by so many people in commenting. The window for consultation is now closed and we are unable to accept any more comments until 21 February 2022. We will now analyse and interpret the new information, and we will post a preliminary decision on this species’s Red List status on this page on 21 February 2022, when discussions will re-open.
Since the publication of the Action Plan for Australian Birds 2020, new information/survey data has/have arisen that alters the assessment as initially proposed. Over the past three generations (12.9 years), the Barren Grounds/Budderoo population has apparently declined by 78% from unknown causes (the area was not burned) (D. Bain in litt. 2022). This population was among the largest (see comment above from Stephen Garnett regarding the abundance estimates of each population as in Bain et al. [2021] vs the current estimation following the new information) and is thought to have caused a decline in the global population of c.32% (if other sites remained stable). Given losses of 300 birds from Nadgee, the total decline over the past three generations could be as high as 39-43%. The cause of these declines has not been identified and appears to be at least partially site-specific, with other populations remaining stable over the same time period.
Consequently, the decline is only suspected (precautionarily) to be continuing and the future rate of decline is considered inestimable. The rate of decline over the past three generations, and in the window 2010-2023, has been set to 30-49% to incorporate uncertainties with the data.
The comment from Stephen Garnett regarding the number of locations is accepted, and the number for this species revised to 11-100, accepting that a larger number of fires would be needed to extirpate populations of this species from any single site.
Therefore, our preliminary proposal for the 2022.1 Red List would be to list Eastern Bristlebird as Vulnerable under Criteria A2bc+4bc.
There is now a period for further comments until the final deadline on 27 February 2022, after which the recommended categorisations will be put forward to IUCN.
The final 2022.1 Red List categories will be published on the BirdLife and IUCN websites in July 2022, 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 by so many people in commenting. The window for consultation is now closed and we are unable to accept any more comments. We will analyse and interpret the new information, and we will post a final decision on this species’ Red List status on this page on 7 March 2022.
Recommended categorisation to be put forward to IUCN
The final categorisation for this species has not changed, but the account for this species has been updated to incorporate additional information from this discussion. Eastern Bristlebird is recommended to be listed as Vulnerable under Criteria A2bc+4bc.
Many thanks for everyone who contributed to the 2022.1 GTB Forum process. The final 2022.1 Red List categories will be published on the BirdLife and IUCN websites in July 2022, following further checking of information relevant to the assessments by both BirdLife and IUCN.
We have recently received information via email (D. Bain in litt.) that a 78% decline at Barren Gounds/Budderoo and an 81% decline at Nadgee has been estimated following recent fires. These data were not accounted for in the species account in APAB. This information is currently being considered by the Red List Team to determine whether it alters the proposal herein.
Alex
This new information has important implications for the status of the Eastern Bristlebird. The Barren Grounds/Budderoo subpopulation was one of the largest so a decline of 78% in the last three generations (11 years) from unknown causes (since the area was not burnt), combined with losses from Nadgee/Howe Flat from the 2020 fires, unfortunately would appear to return the species to the status of Vulnerable depending on the population size of Beecroft peninsula.
Historical population data do make things confusing but here is a potted summary based on action plans.
In the 2010 Action Plan the population was estimated at 2550 individuals overall but the maximum totals for the subpopulations was there were estimated to be 1250 at Barren Grounds/Budderoo, 1100 at Jervis Bay (including Bherwerre and Beecroft Peninsulas, birds having been introduced to the latter in 2003-5), 50 at Cataract, 10 at Red Rocks, 300 at Nadgee & Howe Flat, and 31 in the north – a total of 2760.
By 2018 the estimate was raised to 2835 in the Threatened Species Commissioners interim report
In the 2020 Action Plan that forms the basis of the account given here, the total is 3000 which includes many of exactly the same figures from 2010 – 1250 at Barren Grounds/Budderoo, 1100 at Jervis Bay (but noting that the population on Beecroft Peninsula is unknown and densities there were high), 50 at Cataract, 10 at Red Rocks, 350 at Nadgee (it was as high as 400 before the fires but mortality of up to 11% was estimated) and 150 at Howe Flat, and 31 in the north – a total of 2941.
Given the declines reported by David Bain, the losses of nearly 1000 birds from Barren Grounds/Budderoo represent a loss of 32% had there been no losses at Nadgee, though would be below if the population on Beecroft Peninsula is >250 higher than estimated. Such losses are dramatic given that Budderoo had the highest density ever recorded in 2019. Given losses of over 300 birds from Nadgee, the total decline since 2019 could be as high as 43%, or 39% since 2010. The losses would still exceed 30% since 2019 unless the Beecroft Peninsula was >1400 birds additional to those counted (or >900 for 2010 estimates).
There is thus a strong argument that the Eastern Bristlebird be listed as VU: A2bc, especially as there have been no recent surveys at many locations from which population estimates have been made, so considerable uncertainty.
I think there is insufficient evidence to say this rate of loss is continuing (Criterion A4) or operate over the next 3 generations (A3).
I also think that recent evidence does not support listing under Criterion B. The survival of birds at Nadgee, despite a ferocious fire, and evidence of Western Bristlebirds escaping to the unburnt fringes of habitat and remaining there until their heaths recover (Mcnee et al. 2021), make it likely that many of the populations live in multiple locations with respect to the threat of fire, and no other threat is permanently removing their habitat.
McNee, S., Newbey, B., Comer, S. and Burbidge, A.H., 2021. Western Bristlebird Dasyornis longirostris: Response to fire and persistence of home range in the Fitzgerald River National Park, Western Australia. Australian Field Ornithology, 38.
Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested by so many people in commenting. The window for consultation is now closed and we are unable to accept any more comments until 21 February 2022. We will now analyse and interpret the new information, and we will post a preliminary decision on this species’s Red List status on this page on 21 February 2022, when discussions will re-open.
Preliminary proposal
Since the publication of the Action Plan for Australian Birds 2020, new information/survey data has/have arisen that alters the assessment as initially proposed. Over the past three generations (12.9 years), the Barren Grounds/Budderoo population has apparently declined by 78% from unknown causes (the area was not burned) (D. Bain in litt. 2022). This population was among the largest (see comment above from Stephen Garnett regarding the abundance estimates of each population as in Bain et al. [2021] vs the current estimation following the new information) and is thought to have caused a decline in the global population of c.32% (if other sites remained stable). Given losses of 300 birds from Nadgee, the total decline over the past three generations could be as high as 39-43%. The cause of these declines has not been identified and appears to be at least partially site-specific, with other populations remaining stable over the same time period.
Consequently, the decline is only suspected (precautionarily) to be continuing and the future rate of decline is considered inestimable. The rate of decline over the past three generations, and in the window 2010-2023, has been set to 30-49% to incorporate uncertainties with the data.
The comment from Stephen Garnett regarding the number of locations is accepted, and the number for this species revised to 11-100, accepting that a larger number of fires would be needed to extirpate populations of this species from any single site.
Therefore, our preliminary proposal for the 2022.1 Red List would be to list Eastern Bristlebird as Vulnerable under Criteria A2bc+4bc.
There is now a period for further comments until the final deadline on 27 February 2022, after which the recommended categorisations will be put forward to IUCN.
The final 2022.1 Red List categories will be published on the BirdLife and IUCN websites in July 2022, 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 by so many people in commenting. The window for consultation is now closed and we are unable to accept any more comments. We will analyse and interpret the new information, and we will post a final decision on this species’ Red List status on this page on 7 March 2022.
Recommended categorisation to be put forward to IUCN
The final categorisation for this species has not changed, but the account for this species has been updated to incorporate additional information from this discussion. Eastern Bristlebird is recommended to be listed as Vulnerable under Criteria A2bc+4bc.
Many thanks for everyone who contributed to the 2022.1 GTB Forum process. The final 2022.1 Red List categories will be published on the BirdLife and IUCN websites in July 2022, following further checking of information relevant to the assessments by both BirdLife and IUCN.