Tawny Eagle (Aquila rapax): revise global status?

Tawny Eagle (Aquila rapax) is a widespread raptor species found across Sub-Saharan Africa and the South Asian subcontinent, with isolated populations in North Africa and the Middle East (see Ferguson-Lees and Christie 2001, Kemp and Kirwan 2017). Most populations are largely resident, though the species will make seasonal movements in some areas (Ferguson-Lees and Christie 2001, Kemp and Kirwan 2017), favouring more open wooded areas, and avoiding dense forest and completely open desert (see Ferguson-Lees and Christie 2001, Kemp and Kirwan 2017).

Tawny Eagles feed on a wide range of prey, both vertebrate and invertebrate, and scavenge at carcasses, road-kills and slaughterhouses (see Ferguson-Lees and Christie 2001, Kemp and Kirwan 2017). This feeding behaviour could be having a major impact on the species, as has already been noticed in Old-world Vultures. The species may face deliberate and incidental poisoning at carcasses in Africa, and may be persecuted by farmers (see Taylor 2015); and while the impact of NSAIDs on this species is not clear, a congener, the Steppe Eagle (Aquila nipalensis), has recently been shown to be affected by diclofenac (Sharma et al. 2014).

The species is also affected by a range of other threats including collisions with traffic when feeding on road-kill, drowning in reservoirs, habitat degradation leading to the loss of nesting sites, and electrocution as a result of collisions with power lines (see Taylor 2015). Overall, the threats that Tawny Eagle faces appear to be driving potentially rapid declines at least across Africa, and the species may be becoming increasingly dependent on protected areas there (e.g. Thiollay 2006, 2007, Virani et al. 2011, Simmons 2015, Taylor 2015).

Given these declines the species will now be compared to all Red List criteria based on the current best information.

 

Criterion A – The Red Data Book of South Africa, Lesotho and Swaziland assessed the rate of decline as >60% over the past 50 years (Taylor 2015), and in Namibia the decline has been estimated at 63% over 30 years (Simmons 2015) (roughly equating to a decline of 80.8% over 3 generations [49.8 years]). Declines elsewhere in Africa have also been rapid, estimated in Burkina Faso, Mali and Niger at >87% between 1969-1973 and 2000-2004 (Thiollay 2006); and 28% between 1976-1988 and 2003-2005 in the Masai Mara, Kenya (Virani et al. 2011), roughly equivalent to 43.1-66.4% over 3 generations.

The status of the species in India is uncertain, however. Given the well-reported declines in vultures in this region it would be surprising if declines in this species had gone unnoticed; but if the species is affected by NSAIDs it may be appropriate to say that it is declining there too. The population of this species in South Asia does seem to be considerably less than that of Africa; with the global population estimated in 2001 as within the range of 100,000-999,999 individuals by Ferguson-Lees and Christie, whereas the population in South Asia was estimated at between 10,000-99,999 individuals. This would suggest that even if the population in South Asia was stable, the global population may still be in rapid decline.

For the species to be listed as Vulnerable under this criterion, the global rate of decline should be at least suspected to fall in the range 30-49% over three generations, whereas to list the species as Endangered or Critically Endangered, the rate of decline should fall in the range 50-79% or >80% respectively, over the same time frame.

It may be tentatively assumed that declines have taken place throughout its African range (given the spread of areas where declines have been reported), although it may be inappropriate to assume these declines extend into its South Asian range. Therefore, if the population in South Asia is considered to be stable, the overall rate of decline likely falls either in the range for Vulnerable or Endangered. Further information about population trends in South Asia are therefore sought to better assess which category this species meets under criterion A.

 

Criterion B – At 52,700,000km2, the Extent of Occurrence far exceeds the threshold for Vulnerable under criterion B, and the Area of Occupancy is also strongly suspected to greatly exceed the threshold for Vulnerable.

 

Criteria C and D – Even though the population size is considered to have declined (potentially considerably) since the estimate of Ferguson-Lees and Christie (2001), the overall population size is still likely too large to approach the thresholds for Vulnerable under these Criteria.

 

Criterion E – To the best of our knowledge no quantitative analysis on extinction risk has been conducted.

 

We therefore request any further information regarding population trends across its range, but particularly in South Asia; though given the reported rates of decline the species likely warrants uplisting to at least Vulnerable or Endangered under criteria A2bcde+3bcde+4bcde.

 

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

Ferguson-Lees, J.; Christie, D. A. 2001. Raptors of the world. London: Christopher Helm.

Kemp, A. C.; Kirwan, G. M. 2017. Tawny Eagle (Aquila rapax). 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 http://www.hbw.com/node/53156 on 19 October 2017).

Sharma, A. K.; Saini, M.; Singh, S. D.; Prakash, V.; Das, A.; Dasan, R. B.; Pandey, S.; Bohara, D.; Galligan, T. H.; Green, R. E.; Knopp, D.; Cuthbert, R. J. 2014. Diclofenac is toxic to the Steppe Eagle Aquila nipalensis: widening the diversity of raptors threatened by NSAID misuse in South Asia. Bird Conservation International 24: 282-286.

Simmons, R. E. 2015. Tawny Eagle Aquila rapax. In: Simmons, R. E.; Brown, C. J.; Kemper, J. (ed.), Birds to watch in Namibia: red, rare and endemic species, pp. 127-129. Ministry of Environment and Tourism, Namibia Nature Foundation.

Taylor, M. R. 2015. Tawny Eagle Aquila rapax. In Taylor, M. R., Peacock, F. & Wanless, R. M. (eds). The 2015 Eskom Red Data Book of Birds of South Africa, Lesotho and Swaziland. BirdLife South Africa, Johannesburg, South Africa.

Thiollay, J.-M. 2006. The decline of raptors in West Africa: long-term assessment and the role of protected areas. Ibis 148: 240-254.

Thiollay, J.-M. 2007. Raptor declines in West Africa: comparisons between protected, buffer and cultivated areas. Oryx 41: 322-329.

Virani, M. Z.; Kendall, C.; Njoroge, P.; Thomsett, S. 2011. Major declines in the abundance of vultures and other scavenging raptors in and around the Masai Mara ecosystem, Kenya. Biological Conservation 144: 746-752.

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