Archived 2018 topic: Black Swift (Cypseloides niger): revise global status?

Currently listed as Least Concern (see BirdLife International 2018), Black Swift (Cypseloides niger) is known to breed in western North America, from southern Alaska and western Canada into south-west U.S.A. and central Mexico, and south through Central America to Costa Rica. These populations are considered probably migratory, but their non-breeding ranges are not certain, although western Brazil has been identified as one potential area (Beason et al. 2012). The species also occurs in the West Indies, with subspecies C. n. niger occurring from Cuba east to Trinidad, and this subspecies may only be a partial migrant (see Chantler et al. 2018). The species appears to prefer forested highlands but, within North America at least, it may occur in a variety of more open habitats too (see Chantler et al. 2018).

The species appears to be declining (Rosenberg et al. 2016, Sauer et al. 2017), yet the threats facing it are currently uncertain, although Rosenberg et al. (2016) suggest that climate change could be a key threat (presumably due to its higher altitude preferences). Additionally, the species’s insectivorous feeding habits may make it vulnerable to pesticide use; and further work to identify its non-breeding key habitat requirements and full range could also identify whether there are any important threats there that are impacting the species, or potentially driving these declines.

Following the publication of Partners in Flight (PiF) Landbird Conservation Plan (Rosenberg et al. 2016) and The State of North America’s Birds 2016 (North American Bird Conservation Initiative 2016) we have reviewed the new information held in these publications, particularly regarding population trends. This has allowed us to reassess the species outlined in these publications against IUCN Red List Categories and Criteria. As the PiF data are long-term trends (1970-2014), where possible we have also used data from the North American Breeding Bird Survey (Sauer et al. 2017) to assess more recent trends over the period relevant to the Red List. Having completed this review, Black Swift appears to warrant a change in Red List status. Therefore, we present here our reassessment against all criteria for the species.


Criterion A – Rosenberg et al. (2016) suggest the species’s population has reduced by 94% between 1970 and 2014, which would equate to a reduction of 78.4% over three generations (24 years), assuming a constant rate of decline. Partners in Flight also present a future half-life of only 16 years for the species, which would equate to a reduction of 64.6% over three generations.

Looking at data from 1994-2015 from Sauer et al. (2017) and extrapolating the trend forward to 2018 (i.e. the time covered by the past three generations), gives an annual decline of 5.3% (0.71-9.00%). This equates to a reduction of 72.9% (15.7-89.6%) over the 24 years, although do note that the data is noted as having a deficiency.

These data are only for U.S.A. and Canada though, and Rosenberg et al. (2016) estimate that only c.35% of the global population occurs in these two countries. Taking this into account, and making a very rough assumption that all other subpopulations are stable, would still give an estimated 45% overall reduction over the past three generations, and declines are continuing. Therefore, the species likely warrants listing at least as Vulnerable under criteria A2ace+3ce+4ace, although if there is any further evidence to back up these trends, especially from the species’s range outside of U.S.A. and Canada, then it could even warrant listing as Endangered.


Criterion B – The species’s range is far too large to warrant listing under this criterion (Extent of Occurrence [breeding/resident] = 13,000,000km2; Extent of Occurrence [non-breeding] = 1,110,000km2).


Criterion C – Rosenberg et al. (2016) estimate the population size to be 210,000 mature individuals. This is too large to warrant listing under this criterion.


Criterion D – The species’s population size and range are too large to warrant listing under this criterion.


Criterion E – To the best of our knowledge there has been no quantitative analysis of extinction risk conducted for this species. Therefore, it cannot be assessed against this criterion.


Therefore, Black Swift warrants uplisting at least to Vulnerable. Any comments or further information regarding population trends from outside of U.S.A. and Canada are welcome, and could mean that the species may even warrant listing as Endangered. Please note, though, that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of the species’ Red List status. Therefore, please make sure your comments are about the proposed listing.



Beason, J. P. Gunn, C.; Potter, K. M.; Sparks, R. A.; Fox, J. W. 2012. The Northern Black Swift: migration path and wintering area revealed. Wilson J. Ornithol. 124(1): 1-8.

BirdLife International. 2018. Species factsheet: Cypseloides niger. Downloaded from on 14/03/2018.

Chantler, P.; de Juana, E.; Boesman, P. 2018. Black Swift (Cypseloides niger). 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. (retrieved from on 14 March 2018).

North American Bird Conservation Initiative. 2016. The State of North America’s Birds 2016. Environment and Climate Change Canada, Ottawa, Ontario.

Rosenberg, K. V., Kennedy, J. A., Dettmers, R., Ford, R. P., Reynolds, D., Alexander, J. D., Beardmore, C. J., Blancher, P. J., Bogart, R. E., Butcher, G. S., Camfield, A. F., Couturier, A., Demarest, D. W., Easton, W. E., Giocomo, J. J., Keller, R. H., Mini, A. E., Panjabi, A. O., Pashley, D. N., Rich, T. D., Ruth, J. M., Stabins, H., Stanton, J. and Will., T. 2016. Partners in Flight Landbird Conservation Plan: 2016 Revision for Canada and Continental United States. Partners in Flight Science Committee.

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.

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1 Response to Archived 2018 topic: Black Swift (Cypseloides niger): revise global status?

  1. James Westrip (BirdLife) says:

    Preliminary proposals

    Based on available information, our preliminary proposal for the 2018 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 2018 Red List categories will be published on the BirdLife and IUCN websites in November, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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