Ludwig’s Bustard

Filed under: High Risk Terrestial Birds |

This species has been uplisted to Endangered as recent research has suggested that the population has undergone a very rapid population decline due to collisions with power lines, a trend which is set to continue into the future as successful mitigation measures are yet to be implemented. Research is urgently required to assess the current population size and identify ways to effectively mitigate collisions with power lines.

Taxonomic source(s):  Dowsett and Forbes-Watson (1993), Sibley and Monroe (1990, 1993)

Distribution and population 
Neotis ludwigii has a large range centred on the dry biomes of the Karoo and Namib in southern Africa, being found in the extreme south-west of Angola, western Namibia and in much of South Africa. The global population has been previously estimated at 56,000 to 81,000 individuals. However, this estimate is now approximately 20 years old, and in this time the species is suspected to have declined rapidly as a result of collisions with overhead power lines, for which there is currently no effective mitigation.

Population justification
The global population has been estimated at 56,000-81,000 individuals (Allan 1994). However, given the estimated rates of power line collisions since this estimate, the true population size is likely to be much lower, and a full population census is needed to accurately establish current numbers.

Trend justification
Based on collision rates with power lines from two areas, the best-case scenario indicates a decline of 51% over three generations in South Africa which holds 50-75% of the global population (A. Jenkins et al. in litt. 2009). Given that power lines collisions also occur in Nambia (A. Scott and M. Scott in litt. 2010), and effective mitigation measures are yet to be implemented, a decline of 50-79% is estimated over the 31 year period from 1994-2025 (three generations).

Ecology
This species inhabits open lowland and upland plains with grass and light thornbush, sandy open shrub veld and semi-desert in the arid and semi-arid Namib and Karoo biomes. The breeding season spans from August to December, nesting on bare ground with a clutch of 2-3 eggs. Chick-rearing is conducted solely by females5. Its diet includes invertebrates, some small vertebrates and vegetable matter, including the berries of Lycium oxycladum. There is strong evidence that the species undergoes movement with rains in pursuit of Orthoptera hatchlings, though vegetation remains important. Flocks of up to 70 individuals have been recorded.

Threats
Snares set for mammals on farms have been identified as a threat, however the major threat for the species is collisions with overhead power lines. Collision rates on high voltage transmission lines in the De Aar area of the Karoo may exceed one Ludwig’s Bustard per kilometre per year, and a recent survey found preliminary evidence for this level of mortality on transmission lines across the Karoo, indicating that the problem is widespread7. Given that the extent of power lines in the Karoo is vast and expanding, with already over 25,000 km of lines in place, it is estimated that such collisions alone are already enough to cause a rapid decline in the population and may increase in the future. This threat may be exacerbated as males are more prone to power line collisions than females, which may lead to a reduced effective population size.

Conservation measures underway
Mitigation measures for power line collisions consisting of visual deterrents have been implemented in South Africa by energy supplier Eskom, but have as of yet proved unsuccessful. There is however anecdotal evidence that there has been some success with new variations of migitation measures at certain sites5. In Namibia, NamPower are also working to implement effective mitigation measures.

Conservation measures proposed
Obtain an updated population estimate Measure bustard collision rates across the whole range of Karoo habitats. Improve knowledge of annual movements. Improve knowledge of how the species visually perceives power lines.

 

http://www.birdlife.org/datazone/speciesfactsheet.php?id=2762

http://www.fitzpatrick.uct.ac.za/pdf/Project_LudwigsBustard.pdf

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