Assessing the extinction risk of the great bustard Otis tarda in Africa

Abstract

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.

Changes in bird‐migration patterns associated with human‐induced mortality

“…; Palacín et al. ). Many of their populations are declining, and all 26 bustard species are threatened (IUCN ).…”

“…Collision with power lines is also a main cause of mortality for other threatened bustards species (Jenkins et al 2010;Silva et al 2010;Dutta et al 2011;Martin 2011). In these species, migration mortality may limit population growth because bustards' demography is sensitive to small changes in adult survival (Combreau et al 2001;Palacín et al 2016). Many of their populations are declining, and all 26 bustard species are threatened (IUCN 2015).…”

Conservation Strategy and Action Plan for the Great Bustard (Otis tarda) in Morocco 2016-2025

“…Additional censuses were conducted in 2003, 2004, 2006 and 2007 yielding total counts respectively of 45, 42, 60 and 77 birds (Arhzaf 2010) (these data are not shown in Table 1, which focuses on the total estimated population size). The dynamics and trend of the Moroccan Great Bustard population between 1999 and 2014 were studied by Palacín et al (2016), who provide additional total counts of 49 birds in 2009, 41 in 2011 and 34 in 2014. During the census of the Moroccan population of Great Bustard on 9-13 March 2015 covering the seven previously identified lek areas, 40-44 bustards were found only in two areas -Araoua and Tleta-Rissana (Figures 2 and 3), although all previous lek areas were visited, resulting in a new population estimate of 45-50 birds (Alonso et al 2015).…”

“…Threats have been described and detailed by Hellmich and Idaghdour (2002), Alonso et al (2005), Arzahf 2010and Qninba (2016), and were also listed and ranked by the stakeholder workshop participants. In addition, Palacín et al (2016) analysed the growth in infrastructure between 2005 and 2014. Full accounts of threats are thus not given below, rather an overview of threats to guide the development of the action plan.…”

“…• Agricultural intensification, including use of chemicals Great Bustards cannot survive in an intensively managed agricultural landscape, especially large expanses of monoculture, where there is the added threat of mechanical harvesting. Palacín et al (2016) • Loss of habitat Loss of habitat is largely due to agricultural intensification. A particular threat is the loss of natural cover.…”