Sex-biased juvenile survival in a bird with extreme size dimorphism, the great bustard Otis tarda

Martín, Carlos A.; Alonso, Juan Carlos; Alonso, Javier; Palacı́n, Carlos; Magaña, Marina; Martín, Beatriz

doi:10.1111/j.0908-8857.2007.03811.x

Cited by 31 publications

(56 citation statements)

References 55 publications

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“…This probably occurs because males are much larger, heavier and less able to avoid aerial obstacles (Janss 2000, and it may explain the female bias among Ludwig's Bustards (Allan 2005). Similar male-biased collision mortality has been suggested to exaggerate female-biased sex ratios among local populations of Great Bustards (Martín et al 2007). Given the polygamous mating system (Allan 2005), loss of males will have less demographic impact than loss of females, provided the population remains reasonably large.…”

Section: Discussionmentioning

confidence: 77%

Estimating the impacts of power line collisions on Ludwig’s Bustards Neotis ludwigii

Jenkins

Shaw

Smallie

et al. 2011

Bird Conservation International

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SummaryLudwig's Bustard Neotis ludwigii, endemic to Africa's south-west arid zone, is susceptible to collisions with overhead power lines. Limited data from the south-eastern part of its range suggest that this factor may threaten its survival. We estimated transmission line collision rates for Ludwig's Bustard across its South African range to assess the effect of this mortality on the population. Conservatively, collision rates averaged at least 0.63 6 0.12 fatal collisions per km of transmission line per year, with relatively little regional variation. Despite being less abundant, the larger males were more collision-prone than females, which might account for the femalebiased population. Extrapolating collision rates across the range of the species suggests that 4,000-11,900 birds are killed annually on high-voltage transmission lines. Actual mortality on overhead lines is probably much greater, given biases in carcass detection (crippling, scavenging and habitat biases), as well as the fact that our estimate excludes mortality on lower voltage distribution lines and telephone wires. Given an estimated global population of 56,000-81,000 birds in the late 1980s, the demographic invariant method suggests that such mortality is unsustainable. This result supports the recent upgrading of the conservation status of Ludwig's Bustard from 'Least Concern' to 'Endangered', and highlights the need for further research on this problem.

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Section: Discussionmentioning

confidence: 77%

Estimating the impacts of power line collisions on Ludwig’s Bustards Neotis ludwigii

Jenkins

Shaw

Smallie

et al. 2011

Bird Conservation International

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“…These land-use changes surely have a negative impact on population survival through a reduction in food availability, but may also, and perhaps more importantly, have an impact through direct mortality due to collisions with power lines. Power line casualties represent the main human-induced mortality factor affecting great bustards (Martín et al 2007, Barrientos et al 2012, Raab et al 2012, and may limit population growth in this species (Martín 2008). Since 2005, at least 19 km of new power lines have been constructed in great bustard core areas in Morocco (Table 1) great bustards, since collision mainly affects adult mortality, which is one of the demographic parameters with the greatest effect on lambda (Martín 2008).…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, input parameters to build the models were based on the best monitored Iberian population inhabiting a similar humanized habitat. This data set was ob tained by long-term monitoring of the population dynamics based on 100s of radiotracked birds and at least 2 seasonal censuses conducted each year from 1995 to the present: one census in spring to count breeding individuals and another in mid-September to determine the annual productivity (Alonso et al 2004a, Martín et al 2007, Martín 2008. When parameters from the study population are not obtainable, it is justified to use reliable VORTEX parameters obtained for other populations of the same species (e.g.…”

Section: Pva Modelmentioning

confidence: 99%

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

Palacı́n

Martín²,

Onrubia³

et al. 2016

Endang. Species. Res.

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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.

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“…Sex ratio in wild populations elsewhere is variable (Oparin et al 2003;Martín et al 2007); in the 167 UK population sex ratio is relatively equal, therefore we have assumed an equal sex ratio in the 168 analysis. We modelled 10 scenarios (Table 4).…”

Section: Population Modelling 160mentioning

confidence: 99%

Impacts of survival and reproductive success on the long-term population viability of reintroduced great bustards Otis tarda in the UK

Ashbrook

Taylor

Jane

et al. 2015

Oryx

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Word count: 6,274 12 13 14 2 Reintroductions aim to re-establish species within their historical ranges through the release of wild-15 or captive-bred individuals following extirpation (or extinction) in the wild. While there is no general 16 agreement on what constitutes a successful reintroduction, the probability of the population achieving 17 long-term persistence should be addressed. Here, we review a 10-year trial reintroduction of the great 18bustard Otis tarda, a globally-threatened bird species, to the UK and assess long-term population 19 viability. Despite changes in rearing and release strategy, initial post-release survival probability 20 remained consistently low, with only 11.3% of bustards (n = 167) surviving from release to one year 21 post-release. Nineteen breeding attempts were made by eight females; however, only one chick 22 survived more than 100 days from hatching, and no wild juveniles have recruited into the population. 23Using demographic rates from the UK population and wild populations elsewhere and stochastic 24 population modelling, we investigate the viability of this reintroduced population by predicting 25 population size over the next ten years. Under current demographic rates the population was predicted 26 to decline rapidly. Self-sufficiency was only predicted using the highest estimates from the UK 27 population both for first-year and adult survival, and recruitment rates from wild populations 28 elsewhere. Although changes have been made in rearing, release strategies, habitat management and 29 release sites used, these changes appear to have modest impact on long-term viability. Substantial 30 improvements in survival rates and productivity are required in order to establish a viable great 31 bustard population in the UK, and we consider this unlikely. 32 33

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Sex-biased juvenile survival in a bird with extreme size dimorphism, the great bustard Otis tarda

Cited by 31 publications

References 55 publications

Estimating the impacts of power line collisions on Ludwig’s Bustards Neotis ludwigii

Estimating the impacts of power line collisions on Ludwig’s Bustards Neotis ludwigii

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

Impacts of survival and reproductive success on the long-term population viability of reintroduced great bustards Otis tarda in the UK

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