Chuck-will’s-widow (Antrostomus carolinensis): revise global status?

Currently listed as Least Concern (BirdLife International 2018), Chuck-will’s-widow (Antrostomus carolinensis) is a migratory species of the Americas. It breeds in south-east Canada and eastern U.S.A. preferring wooded (particularly deciduous and mixed) habitats, although it will venture in suburban areas, pasture and open areas (Straight and Cooper 2012, Cleere and Kirwan 2018). It overwinters from southern U.S.A., through eastern Mexico, Central America, the Caribbean, and into northern South America.

The species appears to be threatened by a range of factors including the degradation of its habitat for urban development, and the species’s habit of utilising roads for dust baths etc. at night mean it is at risk from collisions with cars (see Straight and Cooper 2012). Changes in habitat may also be bringing the species more into contact with competitors such as Eastern Whip-poor-will. As the latter’s range alters it may potentially be causing indirect impacts on Chuck-will’s-widow, although there is little direct evidence for this currently (see Straight and Cooper 2012), and Eastern Whip-poor-will itself is thought to be declining rapidly (Rosenberg et al. 2016). Chuck-will’s-widow is also very sensitive to disturbance, and could be affected by pesticide use as it is insectivorous, and will feed over pasture (see Straight and Cooper 2012).

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, Chuck-will’s-widow 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 a population reduction of 63% between 1970 and 2014. This would equate to a decline of 31.6% over three generations (16.8 years). More current trends from Sauer et al. (2017) show an annual decline of 1.73% (1.01-2.44%) between 2005 and 2015. This would equate to a decline of 25.4% (15.7-34.0%) over three generations.

Sauer et al. (2017) do also show year by year records, and so we can extrapolate trends for any three generation period. Three generations ago is approximately 2001. Therefore, we can extrapolate the trends between 2001 and 2015 to 2018 in order to estimate the population trend over the past three generations. Between 2001 and 2015 the population has been, in general, decreasing with a significant, estimated annual decrease of 1.86% (1.33 to 2.40%) (Sauer et al. 2017). This would equate to a reduction of 27.1% (20.1-33.5%) over three generations, and ongoing declines appear to be at a similar rate.

Therefore, rate of decline likely approaches the threshold for Vulnerable under this criterion (reduction of 30% over three generations). Therefore, the species likely warrants uplisting to Near Threatened under criteria A2ace+3ce+4ace.

 

Criterion B – The species’s range is far too large to warrant listing under this criterion (Extent of Occurrence [breeding/resident] = 3,570,000km2; Extent of Occurrence [non-breeding] = 7,160,000km2).

 

Criterion C – Rosenberg et al. (2016) estimate the population size to be 5,400,000 mature individuals, and so this is far too large to warrant listing under this criterion.

 

Criterion D – The species’s population size and range are far 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, Chuck-will’s-widow warrants uplisting to Near Threatened. We welcome any comments or further information but please note 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.

 

References

BirdLife International. 2018. Species factsheet: Antrostomus carolinensis. Downloaded from http://www.birdlife.org on 05/03/2018.

Cleere, N.; Kirwan, G.M. 2018. Chuck-will’s-widow (Antrostomus carolinensis). 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 https://www.hbw.com/node/55185 on 5 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.

Straight, C. A.; Cooper, R. J. 2012. Chuck-will’s-widow (Antrostomus carolinensis), version 2.0. In: Rodewald, P. G. (ed.). The Birds of North America. Cornell Lab of Ornithology, Ithaca, New York, U.S.A. https://doi.org/10.2173/bna.499.

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2 Responses to Chuck-will’s-widow (Antrostomus carolinensis): revise global status?

  1. James Westrip (BirdLife) says:

    Tim Meehan has kindly provided analyses of Christmas Bird Count data. Taken from long-term trends (1966-2017), these data suggest an annual decline of 2.89% (1.16-4.56% annual decline) in this species. This would equate to a reduction of 38.92% (17.84-54.38%) over three generations.

  2. 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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