Blue Crane (Anthropoides paradiseus): revise global status?

BirdLife species factsheet for Blue Crane

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.

References

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.

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10 Responses to Blue Crane (Anthropoides paradiseus): revise global status?

  1. All threats to the Blue Crane in Namibia are detailed in the species text in the book. These are human encroachment and long-term water availability in Etosha.

    Simmons RE 2015. Blue Crane (Anthropoides paradiseus). In: Birds to Watch in Namibia: red, rare and endemic species. Simmons RE, Brown CJ, Kemper J (eds). Pp 60-63. Ministry of Environment and Tourism, Namibia Nature Foundation, Windhoek.

  2. Christie Craig says:

    Consolidated response from IUCN Crane Specialist Group, International Crane Foundation, Endangered Wildlife Trust, Kevin Shaw (Cape Nature) and Peter Ryan (FitzPatrick Institute of African Ornithology)

    Projecting back three generations (37.5 years), significant increases in the Western Cape population have compensated for the loss of the Blue Crane stronghold in the grasslands. The Western Cape population is dependent on the current wheat- pasture mosaic and access to artificial water points. Blue Cranes are also subject to threats such as powerline collisions (Shaw et al. 2010), fence entanglements, breeding disturbance and occasionally conflict with farmers (van Velden et al. 2016). This and potential changes to the agricultural landscape with climate or socio-economic change call into question the stability of this artificial population. Hofmeyr (2012) showed significant increases in the Overberg and Swartland regions of the Western Cape, however we have since updated this analysis to include the last 10 years of data from the Coordinated Avifaunal Roadcount (CAR) summer surveys along set routes (summer counts were used because Hofmeyr 2012 found summer counts to be more reliable than winter counts for Blue Cranes).

    This analysis shows the Overberg population peaking in 2010 (increasing on average by 13% per annum from 1993-2010), however after 2010 the population trend turned downward, declining on average by 4% per annum from 2011-2019. In the Swartland, where aerial surveys (unpubl. data.) indicate Blue Crane density is 3,5 times lower than the Overberg, CAR counts similarly showed an increasing trend, up until 2007. Since then the trend seems to have largely stabilised, on average the Swartland population increased by 0.05% per annum between 2007 and 2017. Blue Cranes are also routinely counted on the Little Karoo CAR routes at densities on average 1.5 times lower than the Swartland. In the Little Karoo there was similarly an increase in Blue Crane numbers from 2000 to 2009 but from 2010-2018 the numbers counted have been declining on average by 2% per annum. Given that the Little Karoo probably represents the fringes of the Overberg population- this is not surprising. This gives strong evidence that the Western Cape population is no longer increasing. The data shows that there is a decline in this sub-population (a major contribution to the global population) and the reasons for this decline are unclear and concerning.

  3. Christie Craig says:

    continued…
    Analysis of the long-term citizen science datasets in the Nama Karoo indicate a stable or slightly increasing population trend. Comparison of the first (SABAP1; 1987-1991) and second (SABAP2; 2007-2020) South African Bird Atlas Project indicate little significant change in reporting rate (% of atlas records reporting Blue Crane- which has been shown to be a reasonable proxy for abundance- Griffioen, 2001) for this region. Similarly, Eastern Cape Karoo and Eastern Cape Coastal CAR routes indicate stable or slightly increasing trends between 1999 and 2017. Northern Cape Karoo CAR routes are difficult to analyse given a major drop off in participation in the last 10 years- but Hofmeyr (2012) found a slightly increasing trend until 2008.

    The grasslands (formerly the stronghold for the Blue Crane) now hold a small percentage of the total Blue Crane population. Comparing reporting rates between SABAP1 and SABAP2 indicate significant declines in reporting rate over 40% of the area. The analysis of the grassland CAR precincts still need to be updated but descriptive graphs of the trends suggest that trends per precinct have not changed since Hofmeyr (2012)- indicating KwaZulu-Natal grassland precincts declining, and much of the Free State also seeing a declining trend, except for the southern Free State and Wakkerstroom where counts indicate a slight increase.

    Lastly, it is worth noting that recent analyses of data from the South African Bird Atlas Project (SABAP1-SABAP2) indicate that there has been a 5% nett loss of range for Blue Crane from the late 1980’s to date, mainly in the grasslands. This overall range contraction (measured as a quarter degree grid cell going from reporting cranes in SABAP1 to reporting 0 cranes in SABAP 2) occurred despite range expansion in the Western Cape.

  4. Christie Craig says:

    In conclusion, if the Grasslands and Karoo sub-populations stay stable over the next three generations, and declines of the Western Cape population, in the region of 2-3% per annum continue- the global Blue Crane population is expected to decline by 31.8-40.1% over the next three generations. The Blue Crane therefore still meets the criteria for listing as Vulnerable A3cde, and it is premature to down list it at this stage. Particularly as the reasons for the decline in the Western Cape are unclear.

    The regional assessment of the species was undertaken in 2014 and the down listing of the species was based on the increasing Western Cape population. Subsequent monitoring has, however, shown that this population is on the decline and this will need to be taken into account when the next regional assessment is undertaken.

  5. Christie Craig says:

    On a final note, we have considered the generation length for Blue Crane. Bird et al. (2020) come to 12.5 years, based on a survival estimate of 0.91 derived from modelling of life history traits. We are of the opinion that this survival estimate is probably too low- particularly if it is preferable to use pre-disturbance adult survival in calculations of generation length- as per IUCN guidelines. Our best estimate of annual adult Blue Crane survival is 0·96 (95% CI 0·88- 0·99)- from the Karoo (Altwegg & Anderson, 2009), where we expect adult survival to be closer to pre-disturbance levels than the grasslands or Western Cape. This would mean that the estimate of 0.91 is on the lower end of adult survival. Using the adult mortality proxy calculation for generation length (Bird et al. 2020), with an adult survival of 0.96 and age of first breeding at 4.47 (as per Bird et al. (2020), generation length would be calculated at 29.47 years. This means three generations would be 87 years- taking us to 1933 as our baseline for assessing Blue Crane declines. This pre-dates the precipitous declines in the grasslands, whereas looking at three generations at a generation length of 12.5 years, takes us to 1982-at which point much of the grassland declines had already happened.

    This concludes this consolidated response from IUCN Crane Specialist Group, International Crane Foundation, Endangered Wildlife Trust, Kevin Shaw (Cape Nature) and Peter Ryan (FitzPatrick Institute of African Ornithology)

  6. According to available count data, Blue Crane numbers in Namibia show a long term decline (Simmons et al. 2015). The highest counts on record for the Etosha National Park and surrounds are 107 individuals in the 1970s (R Miller pers. comm.) and 138 in 1976 (Berry 1984), thereafter declining to 80 birds in 1992 (Brown 1992) and 60 in 1994 (Simmons et al. 1996). Apart from 51 individuals (excluding chicks) in 2006, regular counts have not exceeded 35 from this time, with a maximum of only 33 in 2019 (Scott et al. 2019; Namibia Crane Working Group in litt.).

    References
    Berry HH 1984. Second total census of Etosha using a helicopter and fixed-wing aircraft. Internal report, Ministry of Environment & Tourism (then Dept of Agriculture & Nature Conservation), Windhoek, Namibia.
    Brown CJ 1992. The status of cranes in Namibia. Pp 73-78 In: Proc. 1st Sthn Afr. Crane Conf. Natal.
    Scott A, Scott M, Altwegg R, Böhme H, Brain C, Gariseb S, Guim S, Kapner J, Kolberg H, Mendelsohn J, Shatumbu G, Simmons R, Versfeld W, Vilho A 2019. Conservation aspects of the Blue Crane in Namibia. Poster presentation for Etosha 112 Symposium, June 2019 (downloadable on http://www.the-eis.com).
    Simmons RE, Trewby I, Trewby M 1996. Are Etosha’s Blue Cranes declining? African Wildlife 50: 32-34.
    Simmons RE 2015. Blue Crane (Anthropoides paradiseus). In: Birds to Watch in Namibia: red, rare and endemic species. Simmons RE, Brown CJ, Kemper J (eds). Pp 60-63. Ministry of Environment and Tourism, Namibia Nature Foundation, Windhoek.

  7. According to available count data, Blue Crane numbers in Namibia show a long term decline (Simmons et al. 2015). The highest counts on record for the Etosha National Park and surrounds are 107 individuals in 1970s (R Miller pers. comm.) and 138 in 1976 (Berry 1984), thereafter declining to 80 birds in 1992 (Brown 1992) and 60 in 1994 (Simmons et al. 1996). Apart from 51 individuals in 2006, regular counts have not exceeded 35 from this time, with a maximum of only 33 in 2019 (Scott et al. 2019; Namibia Crane Working Group in litt.).

    References
    Berry HH 1984. Second total census of Etosha using a helicopter and fixed-wing aircraft. Internal report,
    Ministry of Environment & Tourism (then Dept of Agriculture & Nature Conservation), Windhoek,
    Namibia.
    Brown CJ 1992. The status of cranes in Namibia. Pp 73-78 In: Proc. 1st Sthn Afr. Crane Conf. Natal.
    Scott A, Scott M, Altwegg R, Böhme H, Brain C, Gariseb S, Guim S, Kapner J, Kolberg H, Mendelsohn J, Shatumbu G, Simmons R, Versfeld W, Vilho A 2019. Conservation aspects of the Blue Crane in Namibia. Poster presentation for Etosha 112 Symposium, June 2019 (www.the-eis.com).
    Simmons RE, Trewby I, Trewby M 1996. Are Etosha’s Blue Cranes declining ? African Wildlife 50: 32-34.
    Simmons RE, Brown CJ, Kemper J 2015. Birds to watch in Namibia: red, rare and endemic species. Ministry of Environment and Tourism and Namibia Nature Foundation, Windhoek.

  8. Red List Team (BirdLife International) says:

    Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested by so many people in commenting. The window for consultation is now closed. We will analyse and interpret the new information and post a preliminary decision on this species’s Red List status on this page in early July.

    Thank you once again,
    BirdLife Red List Team

  9. Red List Team (BirdLife International) says:

    Preliminary proposal

    Based on available information, our preliminary proposal for the 2020 Red List would be to list Blue Crane as Vulnerable under Criterion A3cde.

    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 the initial proposal.

    The final 2020 Red List categories will be published on the BirdLife and IUCN websites in December 2020/January 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN. The final publication date will be publicised by IUCN here: https://www.iucnredlist.org/assessment/updates

  10. Red List Team (BirdLife International) says:

    Recommended categorisation to be put forward to IUCN

    Based on available information, our proposal for the 2020 Red List is to pend the decision on this species, awaiting further information on the magnitude of projected reduction across its range. The discussion for Blue Crane will be kept open until 2021, while the current Red List category will remain unchanged in the 2020 update.

    Final 2020 Red List categories will be published on the BirdLife and IUCN websites in December 2020/January 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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