This discussion was first published as part of the 2020 Red List update. At the time a decision regarding its status was pended, but to enable potential reassessment of this species as part of the 2021 Red List update this post remains open and the date of posting has been updated.
Blue Crane (Anthropoides paradiseus) is near-endemic to South Africa, with a small breeding population in northern Namibia. The species’s stronghold is the Western Cape in South Africa, holding about 52% of the population, followed by the Karoo (c. 29% of the population) and the Grasslands, with about 14% of the population (McCann et al. 2007, C. Craig in litt. 2020). The disconnected population in Namibia is very small, numbering only 32 individuals (Namibia Crane Working Group 2018). The minimum global population size has been estimated at c. 25,555 individuals (BirdLife International 2020). More recent estimates based on count data project c. 25,000 individuals in the Western Cape (C. Craig in litt. 2020). Assuming that proportions remain unchanged, the population in the Karoo would number c. 13,900 individuals and the population in the Grasslands would consist of c. 6,200 individuals; the total population in South Africa may number up to 48,000 individuals (C. Craig in litt. 2020). The global population is thus tentatively placed in the band 25,500-48,000 individuals, which roughly equates to 16,000-32,000 mature individuals.
Blue Crane is facing a high number of threats, including direct and accidental poisoning (Barnes 2000, K. Morrison in litt. 2007, T. Smith in litt. 2018) and the loss of grassland habitat to afforestation, mining, agriculture and infrastructural development (Bidwell et al. 2006, K. Morrison in litt. 2007, Shaw et al. 2010, K. Morrison in litt. 2017). A major cause of mortality is the collision with powerlines (K. Morrison in litt. 2007, Shaw et al. 2010, Shaw 2013). Large parts of the population are dependent on man-made agricultural landscapes and are therefore susceptible to future socio-economic, climatic or land-use changes (McCann 2001).
Despite the number and magnitude of threats to the species, the population has been increasing over the past two decades within its stronghold in the Western Cape (Hofmeyr 2012). The population in the Karoo is thought to be stable or potentially increasing (Allan 2005, McCann et al. 2007, Shaw et al. 2015), while the populations in the Grasslands and in Namibia are in decline (Simmons 2015, A. Scott and M. Scott in litt. 2018).
Blue Crane is currently listed as Vulnerable under Criterion A3cde (BirdLife International 2020). However, the current and recent status of the population indicates that both the size of the population and range exceed the thresholds for listing as threatened. In addition, the population trend is believed to be stable or increasing due to high breeding productivity offsetting adult mortality, which regionally is at high levels especially due to collisions with powerlines. Given the apparent population increase, or at least stability, over the past decade, it is not considered likely that the rate of an imminent decline would exceed 30% over the next three generations. Blue Crane may thus warrant a change in Red List status, and will here be assessed against all Red List Criteria:
Criterion A – The population of Blue Crane has undergone severe declines in the past, having halved since the 1970s in South Africa (Archibald and Meine 1996, Barnes 2000). However, these declines seem largely historical, as the population in the Western Cape increased substantially in the last century, although this trajectory has levelled off in the past 10-15 years, and the population in the Karoo stable or increasing in parts of the range. The populations in the Grasslands and in Namibia are thought to be in decline. An overall quantification of the trends is lacking; however, the increase in the Western Cape population and stability of the Karoo population, which together comprise about 80% of the global population, are thought to offset the apparent declines in the much smaller populations in the Grasslands and Namibia.
Nevertheless, modelling potential population trajectories indicated that should breeding success reduce, which is conceivable as current values are thought to be high (Pettifor et al. unpublished 2007), current rates of adult mortality would be unsustainable. Given the long generation length of 12.5 years (Bird et al. 2020)*, a precautionary approach would be to suspect moderately rapid declines in the future in the range of 20-29% over three generations (37.5 years). Therefore, it is proposed that Blue Crane be listed as Near Threatened, approaching the threshold for listing as threatened under Criterion A3cde.
Criterion B – The Extent of Occurrence (EOO) is estimated at 1,890,000 km2. This is too large to warrant a listing as threatened under Criterion B1, and Blue Crane is considered Least Concern under this criterion. The Area of Occupancy (AOO) has not been quantified according to IUCN Guidelines (IUCN Standards and Petitions Committee 2019); thus the species cannot be assessed against Criterion B2.
Criterion C – The population size has been estimated at 25,500-48,000 individuals, roughly equivalent to 16,000-32,000 mature individuals. This is too large to approach the threshold for listing as threatened under Criterion C, and Blue Crane is therefore assessed as Least Concern under this criterion.
Criterion D – The population size and range are too large to warrant a listing as threatened under Criterion D, and Blue Crane is therefore assessed as Least Concern under this criterion.
Criterion E – To the best of our knowledge no quantitative assessment of the probability of extinction has been conducted for this species, and so it cannot be assessed against this criterion.
Based on the above assessment, it is proposed to list Blue Crane (Anthropoides paradiseus) as Near Threatened,approaching the threshold for listing as threatened underCriterion A3cde. Available evidence suggests that the species crossed the threshold for downlisting to NT at the latest between 2012 and 2016, when past declines appear to have stabilised. We welcome any comments on the proposed listing and specifically ask for information regarding the timing of changes.
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. By submitting a comment, you confirm that you agree to the Comment Policy.
*Bird generation lengths are estimated using the methodology of Bird et al. (2020), as applied to parameter values updated for use in each IUCN Red List for birds reassessment cycle. Values used for the current assessment are available on request. We encourage people to contact us with additional or improved values for the following parameters; adult survival (true survival accounting for dispersal derived from an apparently stable population); mean age at first breeding; and maximum longevity (i.e. the biological maximum, hence values from captive individuals are acceptable).
An information booklet on the Red List Categories and Criteria can be downloaded here and the Red List Criteria Summary Sheet can be downloaded here. Detailed guidance on IUCN Red List terms and definitions and the application of the Red List Categories and Criteria can be downloaded here.
Allan, D. G. 2005. Blue Crane Anthropoides paradiseus. In: Hockey, P. A. R.; Dean, W. R. J.; Ryan, P. G. (ed.), Roberts – Birds of Southern Africa, VIIth ed., pp. 302-304. The Trustees of the John Voelcker Bird Book Fund, Cape Town, South Africa.
Archibald, G. W.; Meine, C. D. 1996. Gruidae (Cranes). In: del Hoyo, J.; Elliott, A.; Sargatal, J. (ed.), Handbook of the birds of the world, pp. 60-89. Lynx Edicions, Barcelona, Spain.
Barnes, K.N. 2000. The Eskom Red Data Book of birds of South Africa, Lesotho and Swaziland. BirdLife South Africa, Johannesburg, South Africa.
Bidwell, M. T.; Ryan, P.; Shaw, K. 2006. Habitat selection and reproductive success in Blue Cranes in a South African agricultural landscape. Journal of Ornithology 147(5): 99.
Bird, J.P., Martin, R., Akçakaya, H.R., Gilroy, J., Burfield, I.J., Garnett, S., Symes, A., Taylor, J., Şekercioğlu, Ç.H. & Butchart, S.H. (2020). Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology, online first view.
BirdLife International. 2020. Species factsheet: Anthropoides paradiseus. http://www.birdlife.org (Accessed 21 May 2020).
Hofmeyr, S. D. 2012. Impacts of environmental change on large terrestrial bird species in South Africa: Insights from citizen science data. PhD thesis. University of Cape Town, Cape Town, South Africa.
IUCN Standards and Petitions Committee. 2019. Guidelines for using the IUCN Red List Categoreis and Criteria. Version 14. http://www.iucnredlist.org/documents/RedListGuidelines.pdf.
McCann, K. 2001. Population status of South Africa’s three crane species as of the end of 1999 based on a National Crane Census and regional aerial surveys. 10th Pan-African Ornithological Congress Conference Paper: Ostrich.
McCann, K.; Theron, L-J.; Morrison, K. 2007. Conservation priorities for the Blue Crane (Anthropoides paradiseus) in South Africa – the effects of habitat changes on distribution and numbers. Ostrich 78(2): 205-211.
Namibia Crane Working Group. 2018. Namibia Crane News 57: 1-10.
Pettifor, R. A.; Shaw, K.; Theron L. J.; Morrison, K.; Botha, B.; Franke, U.; Gibbons, B.; Oliver, K.; Ramke, G.; Smith, T.; Gomes, B. unpubl. data. The Importance of the Western Cape sub-population of Blue Cranes to their Global Population in the Face of Climate Change: Implications for Conservation.
Shaw, J. M. 2013. Power line collisions in the Karoo: Conserving Ludwig’s Bustard. PhD thesis. University of Cape Town, Cape Town, South Africa.
Shaw, J. M.; Jenkins, A. R.; Allan, D. G.; Ryan, P. G. 2015. Population size and trends of Ludwig’s Bustard Neotis ludwigii and other large terrestrial birds in the Karoo, South Africa. Bird Conservation International 26: 69-86.
Shaw, J. M.; Jenkins, A. R.; Smallie, J. J.; Ryan, P. G. 2010. Modelling power-line collision risk for the Blue Crane Anthropoides paradiseus in South Africa. Ibis 152: 590-599.