Eastern Whip-poor-will (Antrostomus vociferus): revise global status?

Currently listed as Least Concern (BirdLife International 2018), Eastern Whip-poor-will (Antrostomus vociferus) breeds in southern central and eastern Canada, and east-central and eastern U.S.A., wintering in south-east U.S.A., Mexico and into Central America. The species favours open forest and woodland habitats, although it does appear to tolerate some semi-open, degraded habitats such as farmland, road corridors and logged woodland (Cink et al. 2017, Cleere and Kirwan 2018).

While it may be able to tolerate some habitat degradation, forest loss and degradation appear to be the key threats to this species. Woodland clearance for agriculture and the closing up of forest gaps due to tree succession is thought to lead to local declines (see Cink et al. 2017). Grazing of forest underbrush, used as nesting cover by the species, may also lead to its disappearance (see Cink et al. 2017). The species will also sit at the side of roads, which means it is at high risk from traffic collision, and there are also untested theories that industrial pollution and pesticide use could be reducing prey abundance (see Cink et al. 2017).

Following the publication of Partners in Flight 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 Categories and Criteria. As the data presented come from long-term trends (Partners in Flight trends come from between 1970 and 2014), where possible we have also used data from the North American Breeding Bird Survey (Sauer et al. 2017) to collate more recent trends. Having completed this review, Eastern Whip-poor-will may 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) gives two different values for the population reduction between 1970 and 2014 – 69% and 67%. Assuming exponential decline, these would equate to a decline of 36.1% or 34.5% over three generations (16.8 years) respectively.

Sauer et al. (2017) show year by year population records, and so we can extrapolate trends for any three generation period. Three generations ago was 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 1.67% (0.15 to 2.91%) (Sauer et al. 2017). This would equate to a reduction of 24.6% (2.5-39.1%) over three generations, assuming exponential decline. However, 2005-2015 trends from Sauer et al. (2017) show a non-significant decline of 1.29% per year (between 2.94% decline to 0.71% increase), which would roughly equate to a 19.6% decrease (39.4% decrease to 12.6% increase) over three generations.

This suggests that rapid declines may have in fact been historical, and the species may now be declining at a slower rate. The long term data suggests declines at a rate that would warrant listing as Vulnerable, but the short term data implies that the species would not even approach the threshold for Vulnerable (30% reduction over three generations). However, Sauer et al. (2017) do note that there is some data deficiency in their trend calculation and the credible interval for their trend estimate does include rates of decline that are greater than this threshold. Therefore, the evidence is probably not sufficient to warrant uplisting to Vulnerable, but given the uncertainty over accurate trend information, it could be conservative to instead propose uplisting the species to Near Threatened under criteria A2ac+3c+4ac.

 

Criterion B – The species’s range is far too large to warrant listing under this criterion (Extent of Occurrence [breeding/resident] = 5,180,000km2; Extent of Occurrence [non-breeding] = 3,350,000km2).

 

Criterion C – Rosenberg et al. (2016) estimate the population size to be 1,800,000 mature individuals. This is far too large for the species 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, Eastern Whip-poor-will potentially warrants a change in status, but this is uncertain. It likely doesn’t qualify for being listed as threatened, but it may warrant listing as 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’s Red List status. Therefore, please make sure your comments are about the proposed listing.

 

 

References

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

Cink, C. L.; Pyle, P.; Patten, M. A. 2017. Eastern Whip-poor-will (Antrostomus vociferus), version 3.0. . In: Rodewald, P. G. (ed.). The Birds of North America. Cornell Lab of Ornithology, Ithaca, New York, U.S.A. Retrieved from the Birds of North America: https//birdsna.org/Species-Account/bna/species/whip-p1.

Cleere, N.; Kirwan, G. M. 2018. Eastern Whip-poor-will (Antrostomus vociferus). 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/55193 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.

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