There seems to be an error in the math. EOO = 87,600 km2. Four birds per km2 = 350,400 birds, times 0.1 (10% of mapped range occupied) = 35,040 birds – the minimum pop size estimate. Sounds like the EOO estimate that went into the pop size calculations above is smaller than 87,600 km2.
Be that as it may, I do not believe that a population density estimate from O. leucopleurus in Argentina is representative for O. adela just because they are congeners. For starters, they differ in natural history in that O. leucopleurus is a partial austral migrant (see Herzog et al. 2019, Birds of Bolivia Field Guide) and O. adela a year-round resident. In Bolivia, O adela is not only patchily distributed, but also quite rare in general. Perhaps in the southernmost of the 3 range polygons it is more common, but anywhere else I would think that a density of 4 birds per km2 is pretty high, let alone 12 per km2.
In conclusion, using a density estimate of a congener as a yardstick for this Bolivian near-endemic seems ill-founded to me and likely overestimates the population size of O. adela.
Thank you for your comment!
The population size has not been calculated by multiplying the density with the EOO, but instead by multiplying it with the area of mapped range. The EOO, as defined by IUCN, depicts the spatial spread of the extinction risk. It is quantified as the area covered by a minimum convex polygon around the mapped range and may also include unoccupied sites or areas of unsuitable habitat. In most cases, the EOO is therefore (considerably) larger than the actual range.
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. We will analyse and interpret the new information and post a preliminary decision on this species’s Red List status on this page in early July.
Thank you once again,
BirdLife Red List Team
Based on available information, our preliminary proposal for the 2021 Red List would be to adopt the proposed classifications outlined in the initial forum discussion.
The population size has been recalculated using a density of 4 individuals/sqkm as the upper limit, resulting in a revised value of up to 15,200 individuals, and consequently the population size is now placed in the band 2,500-9,999 mature individuals. Nevertheless, the size of the largest subpopulation in the southern part of the range would still considerably exceed the threshold of 1,000 mature individuals. Overall, in view of the overall low quality of the population size value, the lack of a trend estimate and lack of data from which to infer a continuing decline, as well as the size of the subpopulations, the species cannot be considered approaching the threshold for listing as threatened.
There is now a period for further comments until the final deadline in mid-July, after which the recommended categorisations will be put forward to IUCN.
The final 2021 Red List categories will be published on the BirdLife and IUCN websites in December 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN.
Recommended categorisation to be put forward to IUCN
The final categorisation for this species has not changed. Wedge-tailed Hillstar is recommended to be listed as Least Concern.
Many thanks for everyone who contributed to the 2021 GTB Forum process. The final 2021 Red List categories will be published on the BirdLife and IUCN websites in December 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN.
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Contact the BirdLife Red List Team under redlistteam [at] birdlife [dot] org.