Palacín, C., Martín, B., Onrubia, A. & Alonso, J. C. 2016. Assessing the extinction risk of the great bustard Otis tarda in Africa. Endang Species Res 30: 73–82. doi: 10.3354/esr00726 (Open Access)
We studied the dynamics and trend of the last extant population of great bustards Otis tarda in Africa. Moroccan great bustards are the southernmost population of this species, and thus show the characteristics of a peripheral population: small size, isolation and low gene flow. Available counts indicate a severe population decline (62% in the last 15 yr), as well as a contraction of the species’ distribution. We used a population viability analysis (PVA) to evaluate the quasi-extinction risk and to identify the most important threats. The estimated geometric growth rate of the more realistic of a set of possible scenarios was 0.87 (95% CI: 0.85, 0.89). This implies a 13% annual decline over 50 yr. However, projections derived from these results should be interpreted with caution, because models have a great deal of uncertainty and vital rates from Iberian populations may be different from those of the Moroccan population. PVA showed the negative consequence of human-induced mortality. According to the model that best fits our census data and if present threats remain in the coming years, this peripheral population could go extinct in ca. 20 yr. Agricultural intensification, infrastructure developments and new power lines in rural areas where the species occurs are causing habitat destruction and fragmentation and increasing artificial mortality. Urgent conservation measures, especially to reduce human-induced mortality, are needed to save African great bustards from extinction. We suggest that these findings can be generalized to other peripheral great bustard populations living in highly humanized landscapes.
Great Bustards are still vulnerable to agricultural intensification, power line collision, and other human-induced landscape changes. Their world population is estimated to be between 44,000 and 57,000 individuals, showing a stable demographic trend at present in the Iberian peninsula, its main stronghold, but uncertain trends in Russia and China, and alarming declines in Iran and Morocco, where it will go extinct if urgent protection measures are not taken immediately. Our knowledge of the behaviour and ecology of this species has increased considerably over the last three decades, allowing us to control the major threats and secure its conservation in an appropriately managed cereal farmland. This species became ‘The Bird of the Year’ in Hungary in 2014.
Except from the article:
“Interestingly, numbers of Great Bustards in Iran and Morocco are at present similar to the minimum numbers reached two decades ago in Germany and Austria (in both countries, ca. 60 individuals in the 1990’s; http://www.grosstrappe.at, http://www.grosstrappe.de), which shows that extinction could theoretically be avoided in Iran and Morocco. Unfortunately however, socio-economic conditions in Iran and Morocco are not equal to those in the two central European countries, making the recovery of the species much more difficult. International efforts should be urgently devoted to try to save the Iranian and Moroccan bustards from extinction”.
Horreo, J. L., Alonso, J. C., Palacín, C., & Milá, B. (2014). Genetic structure in Iberian and Moroccan populations of the globally threatened great bustard Otis tarda: a microsatellite perspective. Journal of Avian Biology 45(5): 507–513. doi:10.1111/jav.00401
Patterns of genetic structure and gene flow among populations help us understand population dynamics and properly manage species of concern. Matrilineal mtDNA sequence data have been instrumental in revealing genetic structure at the intraspecific level, but bi-parentally inherited markers are needed to confirm patterns at the genome level and to assess the potential role of sex-biased dispersal on gene flow, particularly in species where males are known to be the main dispersing sex. Here we use microsatellite loci to examine patterns of genetic structure across the range of the great bustard in Iberia and Morocco, an area representing 70% of the world population of this globally threatened species. We used population differentiation statistics and Bayesian analysis of population structure to analyse data from 14 microsatellite loci. These data provide greater resolution than mtDNA sequences, and results reveal the existence of three main genetic units corresponding to Morocco, the northeastern part of Spain, and the rest of the Iberian Peninsula. Our results, together with previous mtDNA data, confirm the genetic differentiation of the northern Africa population and the importance of the Strait of Gibraltar as a barrier to gene flow for both males and females, rendering the Moroccan population a separate management unit of high conservation concern.