Bachman’s Sparrow (Peucaea aestivalis): revise global status?

Bachman’s Sparrow (Peucaea aestivalis) is endemic to U.S.A. occurring on the coastal plains and Piedmont of south U.S.A. The species is generally found in lowland pine woodland, although it may also occur in clear-cut areas with grassy undergrowth and even grasslands away from pine (see Rising 2018). Timber harvesting, habitat fragmentation and fire suppression are all thought to have contributed to the species’s disappearance from the northern part of its range, and it is now uncommon in the south of its range too. Urban development is additionally thought to be impacting the species, especially as it could prevent the restoration of the fire regimes suitable for the species (P. Taillie in litt. 2016). The species also has been reported to suffer mortality as a result of collisions with communications towers (Longcore et al. 2013), and it suffers disturbance in parts of its range due to birdwatchers. As such the species has been thought to have undergone a moderately rapid decline and it is currently listed as Near Threatened under criterion A2c (see BirdLife International 2018).

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, Bachman’s Sparrow appears to potentially 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) show a population reduction between 1970 and 2014 of 76%, which would roughly equate to a reduction of 30.2% over three generations (11.1 years for this species) assuming a constant rate of decline. Short term data (2005-2015) from Sauer et al. (2017) show an annual decline of 3.58% (1.65-5.56%), which would equate to a decline of 32.5% (16.9-47.0%) over three generations, although it is noted that there is data deficiency in this dataset, and when looking between 2007 (three generations ago) and 2015 the decline is non-significant (annual decline of 2.68% [6.78% decrease to 1.41% increase], roughly equating to a reduction of 26.0% [54.1% decrease to 16.8% increase]). Partners in Flight does also provide a half-life (time for the population to halve) for the species, though, of 24 years (Rosenberg et al. 2016), which would equate to a future decline of 27.4% over three generations.

Therefore, the species at least warrants retaining as Near Threatened under this criterion but under an expanded criteria string of A2ac+3c+4ac. Depending on further comments on the confidence we can have in recent population trend data from Sauer et al. (2017) it could even warrant listing as Vulnerable. This would potentially warrant being under the same criteria string – A2ac+3c+4ac – because even though future declines based on the half-life in Rosenberg et al. (2016) suggest a decline of <30% (over 3 generations), the threats that are driving current declines appear to be continuing and it may be precautionary to suspect that declines would therefore continue at a similar rate into the future.

 

Criterion B – The species’s range is far too large to warrant listing under this criterion (Extent of Occurrence [breeding/resident] = 1,650,000km2; Extent of Occurrence [non-breeding] = 1,150,000km2).

 

Criterion C – Rosenberg et al. (2016) estimate the population size to be 190,000 mature individuals. This is too large to warrant listing under this criterion.

 

Criterion D – The species’s range and population size 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, Bachman’s Sparrow at least warrants having an expanded criteria string under a listing of Near Threatened, and potentially warrants uplisting to Vulnerable. 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: Peucaea aestivalis. Downloaded from http://www.birdlife.org on 09/03/2018.

Longcore, T.; Rich, C.; Mineau, P.; MacDonald, B.; Bert, D.G.; Sullivan, L.M.; Mutrie, E.; Gauthreaux Jr., S.A.; Avery, M.L.; Crawford, R.L.; Manville II, A.M.; Travis, E.R.; Drake, D. 2013. Avian mortality at communication towers in the United States and Canada: which species, how many, and where? Biol. Conserv. 158: 410-419.

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

Rising, J. 2018. Bachman’s Sparrow (Peucaea aestivalis). 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/61952 on 9 March 2018).

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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