Henslow’s Sparrow (Passerculus henslowii) is a migratory New World Sparrow of North America, currently listed as Near Threatened due to suspected moderately rapid declines, although there have been positive trends noted recently (see BirdLife International 2018). During the breeding season it occurs in northern and central U.S.A. from Minnesota south to Kansas and northern Oklahoma across to New Hampshire, as well as just into southern Ontario, Canada. In the non-breeding season it moves southwards occurring in states along the Gulf Coast of U.S.A. and along the Atlantic Coast as far north as South and North Carolina (see Herkert et al. 2002, Rising 2018). It predominantly occurs in open areas, occupying native prairies and grassland in the breeding season, and avoiding areas encroached by woodland (Rising 2018). In the non-breeding season, however, it is more tolerant of wooded areas, occurring in open pine forest as well as on prairies, and is most common in pine forest meadows containing wiregrass, Aristida stricta, and broomsledge, Andropogon virginicus (Rising 2018).
The key threat to the species appears to be the degradation of its habitat, both in the breeding and non-breeding range, with grassland lost to agriculture, natural succession of vegetation due to fire suppression, urbanisation and wetland drainage (see Herkert et al. 2002). Additionally, there is evidence for pesticides having an impact on several species that commonly associate with Henslow’s Sparrow (Bartuszevige 2000 per Herkert et al. 2002), and so this could be another potential threat, although its impact on this species in particular is uncertain.
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, Henslow’s Sparrow 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) estimate the population reduction between 1970 and 2014 to be 10%, which would equate to only a reduction of 2.8% over three generations (11.7 years) assuming a consistent rate of decline. However, we know that the species was declining rapidly, but has since begun to stabilise and potential begun to increase too since the creation of large areas of undisturbed habitat through the Conservation Reserve Program (Rising 1996, Herkert et al. 2002, Cooper 2012).
Short term data (2005-2015) from Sauer et al. (2017), which fits far closer to a three generation period in fact shows a non-significant annual 2.68% increase (6.85% increase to 2.35% decrease), although this is flagged as having an important data deficiency. This would roughly equate to an increase of 36.3% (117.1% increase to 24.3% decrease) over three generations.
Therefore, the species no longer appears to approach the threshold under this criterion, and as such would not warrant listing as such. The likelihood is that this has been the case for some time, especially as increases have been noted for >>5 years.
Criterion B – The species’s range is far too large to warrant listing under this criterion (Extent of Occurrence [breeding] = 1,670,000km2; Extent of Occurrence [non-breeding] = 1,500,000km2).
Criterion C – Rosenberg et al. (2016) estimate the population size to be 390,000 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, Henslow’s Sparrow potentially warrants downlisting to Least Concern. 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.
Bartuszevige, A. M. 2000. Organochlorine pesticide contamination in Illinois grassland birds: a test of the endocrine disruption hypothesis. Master’s Thesis, Illinois State Univ., Normal.
BirdLife International. 2018. Species factsheet: Passerculus henslowii. Downloaded from http://www.birdlife.org on 07/03/2018.
Cooper, T. R. 2012. Status Assessment and Conservation Plan for the Henslow’s Sparrow (Ammodramus henslowii). Version 1.0. U.S. Fish and Wildlife Service, Bloomington, Minnesota. 126 pp.
Herkert, J. R.; Vickery, P. D.; Kroodsma, D. E. 2002. Henslow’s Sparrow (Ammodramus henslowii), 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.672.
North American Bird Conservation Initiative. 2016. The State of North America’s Birds 2016. Environment and Climate Change Canada, Ottawa, Ontario.
Rising, J. D. 1996. A guide to the identification and natural history of the sparrows of the United States and Canada. Academic Press, London.
Rising, J. 2018. Henslow’s Sparrow (Passerculus henslowii). 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/61927 on 7 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.