Archived 2020 topic: Vaux’s Swift (Chaetura vauxi) is being split: assessment of newly recognised taxa.

BirdLife species factsheet for Vaux’s Swift

Following a taxonomic reassessment, Vaux’s Swift (Chaetura vauxi) has been split into Vaux’s Swift (C. vauxi) and Andre’s Swift (C. andrei) (see Chesser et al. 2018). The newly-split Vaux’s Swift is a partial migrant with a resident population in Central America and a population breeding in western North America. Andre’s Swift is endemic to northern Venezuela. The habitat requirements of the newly-split Andre’s Swift have not been investigated, but it is likely that, similarly to Vaux’s Swift, it occupies primary and secondary forests in lowland and montane areas (Chantler et al. 2020). Both of the newly recognised taxa appear to be under threat from forest loss, as they depend on old-growth forest for nest and roost sites (Chantler et al. 2020, Schwitters et al. 2020). 

The pre-split taxon was estimated to number 870,000 mature individuals (Partners in Flight 2019). The population size of the newly-split Andre’s Swift has not been estimated directly. However, based on the recorded population density of a congener (Band-rumped Swift Chaetura spinicaudus: 1 mature individual/km2 in French Guiana [Santini et al. 2018]) and the area of the species’s mapped range (81,400 km2), and assuming that around 10% of the range is occupied, the population of Andre’s Swift may number c.8,000 mature individuals. This estimate is highly preliminary and may be corrected if more detailed data becomes available. To account for uncertainty in the estimate, the population size of Andre’s Swift is here placed in the band 2,500-9,999 mature individuals. From this, it follows that the population of the newly-split Vaux’s Swift may number roughly 860,000 mature individuals.

The pre-split species was listed as Least Concern (BirdLife International 2020). However following the taxonomic split, new estimates of population sizes suggest that both species warrant a thorough assessment, which is provided below.

Criterion A:

Vaux’s Swift (C. vauxi)– Thespecies has been undergoing a moderate decline between 1970 and 2017, on average by 1.1% per year (Partners in Flight 2019). This would roughly equate to a decrease of 10.5% over ten years (one generation length is estimated at 2.4 years; Bird et al. 2020*). Data from the North American Breeding Bird Survey (Sauer et al. 2017) allow to estimate short-term trends over the past ten years. We can extrapolate the trends between 2010 and 2015 to 2020 in order to assess the population trend over the past ten years. Between 2010 and 2015, the population has been decreasing with a non-significant, estimated annual decrease of 0.54% (4.76% decrease to 3.99% increase) (Sauer et al. 2017). Extrapolating the reduction to 2020, the rate of decline would amount to 5.3%, although this number is non-significant. Overall, the rate of decline does not meet the threshold for listing as threatened, and Vaux’s Swift is considered Least Concern under Criterion A.

Andre’s Swift (Chaetura andrei) The species is potentially threatened by habitat loss. Deforestation rates have been low within the range; tree cover was lost at a rate of 7% over the past ten years (Global Forest Watch 2020). It is conceivable that population declines are roughly equivalent to forest loss, and Andre’s Swift may be declining at a rate of < 10% over ten years. The species therefore qualifies as Least Concern under Criterion A.

Criterion B:

Vaux’s Swift (C. vauxi) – The Extent of Occurrence (EOO) of Vaux’s Swift has been calculated as c.11,000,000 km2. This is too large to warrant listing as threatened under Criterion B, and the species may be considered Least Concern under this criterion.

Andre’s Swift (C. andrei) – The EOO of Andre’s Swift has been calculated as 406,000 km2. This is too large to warrant listing as threatened under Criterion B, and the species may be considered Least Concern under this criterion.

Criterion C:

Vaux’s Swift (C. vauxi) – The global population is thought to number roughly 860,000 mature individuals. This is too large to meet the threshold for listing as threatened under Criterion C, and the species is thus considered Least Concern under this criterion.

Andre’s Swift (C. andrei) – The population size has preliminarily been placed in the band 2,500-9,999 mature individuals. This number meets the initial threshold for listing as Vulnerable under Criterion C. However, to do so, the species must meet further conditions.

A population decline of <10% over ten years can be inferred from moderately high rates of forest loss. The subpopulation structure has not been assessed. However, considering the fragmentation of the range, it is likely that the species forms several disjunct subpopulations. Assuming that the true population size is closer to the lower end of the estimate, it can precautionarily be assumed that no subpopulation numbers more than 1,000 mature individuals. Overall, Andre’s Swift qualifies as Vulnerable under Criterion C2a(i).

Criterion D:

Vaux’s Swift (C. vauxi)– The population size and range of Vaux’s Swift are too large to warrant listing as threatened under Criterion D and therefore the species is considered Least Concern under this criterion.

Andre’s Swift (C. andrei)– The population size and range of Andre’s Swift are too large to warrant listing as threatened under Criterion D and therefore the species is considered Least Concern under this criterion.

Criterion E – To the best of our knowledge there have been no quantitative analyses of extinction risk carried out for either of these species. Therefore, they cannot be assessed against this criterion.

Therefore, it is proposed that Vaux’s Swift (Chaetura vauxi)be listed as Least Concern and Andre’s Swift (Chaetura andrei) be listed as Vulnerable under Criterion C2a(i). We welcome any comments on this proposed listing and specifically request up-to-date information on the population size and trend of Andre’s Swift.

Please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of its Red List status. Therefore, please make sure your comments are relevant to the discussion outlined in the topic. By submitting a comment, you confirm that you agree to the Comment Policy.

*Bird generation lengths are estimated using the methodology of Bird et al. (2020), as applied to parameter values updated for use in each IUCN Red List for birds reassessment cycle. Values used for the current assessment are available on request. We encourage people to contact us with additional or improved values for the following parameters; adult survival (true survival accounting for dispersal derived from an apparently stable population); mean age at first breeding; and maximum longevity (i.e. the biological maximum, hence values from captive individuals are acceptable).

An information booklet on the Red List Categories and Criteria can be downloaded here and the Red List Criteria Summary Sheet can be downloaded here. Detailed guidance on IUCN Red List terms and definitions and the application of the Red List Categories and Criteria can be downloaded here.

References

Bird, J. P.; Martin, R.; Akçakaya, H. R.; Gilroy, J.; Burfield, I. J.; Garnett, S.; Symes, A.; Taylor, J.; Šekercioğlu, Ç.; Butchart, S. H. M. (2020). Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology online first view.

BirdLife International. 2020. Species factsheet: Chaetura vauxi. http://www.birdlife.org (Accessed 27 March 2020).

Chantler, P.; Boesman, P.; Kirwan, G. M. 2020. Vaux’s Swift (Chaetura vauxi). In: del Hoyo, J.; Elliott, A.; Sargatal, J.; Christie, D. A.; de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona, Spain. https://www.hbw.com/node/55311 (Accessed on 27 March 2020).

Chesser, R. T.; Vaseghi, H.; Hosner, P. A.; Bergner, L. M.; Cortes-Rodriguez, M. N.; Welch, A. J.; Collins, C. T. 2018. Molecular systematics of swifts of the genus Chaetura (Aves: Apodiformes: Apodidae). Molecular Phylogenetics and Evolution 128: 162-171.

Global Forest Watch. 2020. Interactive Forest Change Mapping Tool. http://www.globalforestwatch.org (Accessed 27 March 2020).

Partners in Flight. 2019. Avian Conservation Assessment Database, version 2019. http://pif.birdconservancy.org/ACAD.

Santini, L.; Isaac, N. J. B.; Ficetola, G. F. 2018. TetraDENSITY: A database of population density estimates in terrestrial vertebrates. Global Ecology and Biogeography 27: 787-791.

Sauer, J. R.; Niven, D. K. ; Hines, J. E.; Ziolkowski, Jr, D. J.; Pardieck, K. L.; Fallon, J. E.; Link, W. A. 2017. The North American Breeding Bird Survey, Results and Analysis 1966 – 2015. Version 2.07.2017 USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Schwitters, L. ; Schwitters, D. ; Bull, E. L. ; Collins, C. T. 2020 Vaux’s Swift (Chaetura vauxi), version 1.0. In : Rodewald, P. G. (ed.). Birds of the World. Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/19.2173/bow.vauswi.01 (Accessed 27 March 2020).

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6 Responses to Archived 2020 topic: Vaux’s Swift (Chaetura vauxi) is being split: assessment of newly recognised taxa.

  1. Todd Morris says:

    Um, Vaux’s Swift breeds in WESTERN North America, not eastern.

    • Red List Team (BirdLife International) says:

      Indeed – you are right! Thanks for spotting it. We have corrected the text accordingly.

  2. Red List Team (BirdLife International) says:

    Global Forest Change data on tree cover loss up to 2019 have now been released and made available via Global Forest Watch. Based on these data, over ten years approximately 2.7% of tree cover with >30% canopy cover was lost from within the range of Andre’s Swift (Global Forest Watch 2020). This does not affect the above assessment under Criterion A for Andre’s Swift.

  3. Red List Team (BirdLife International) says:

    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

  4. Red List Team (BirdLife International) says:

    Preliminary proposal

    Based on available information, our preliminary proposal for the 2020 Red List would be to adopt the proposed classifications outlined in the initial forum discussion.

    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.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from those in the initial proposal.

    The final 2020 Red List categories will be published on the BirdLife and IUCN websites in December 2020/January 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  5. Red List Team (BirdLife International) says:

    Recommended categorisation to be put forward to IUCN

    The final categorisations for these species have not changed.
    Vaux’s Swift is recommended to be listed as Least Concern.
    Andre’s Swift is recommended to be listed as Vulnerable under Criterion C2a(i).

    Many thanks for everyone who contributed to the 2020 GTB Forum process. The final 2020 Red List categories will be published on the BirdLife and IUCN websites in December 2020/January 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN.

Comments are closed.