Reassessment of the size of the Scopoli’s Shearwater population at its main breeding site resulted in a tenfold increase: implications for the species conservation

Rau, Pierre Defos du; Bourgeois, Karen; Thévenet, Mathieu; Ruffino, Lise; Dromzée, Sylvain; Ouni, Ridha; Abiadh, Awatef; Estève, Roger; Durand, Jean-Patrick; Anselme, Lorraine; Faggio, Gilles; Yahya, Jaber Mohamed; Rguibi, Hamid; Renda, Michel; Miladi, Bayrem; Hamrouni, Hennabaal; Alilech, Slim; Nefla, Aymen; Jaouadi, Wahbi; Agrebi, Sofiene; Renou, S.

doi:10.1007/s10336-015-1187-4

Cited by 19 publications

(13 citation statements)

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“…Only birds from Tunisia returned consistently earlier (over the two annual cycles) and arrived earlier to the breeding grounds. Such unexpected pattern was likely related to the size of the sampled colony (i.e., Zembra Island), the largest in the Mediterranean, that hosts more than 75% of the world's breeding population of the species (Defos du Rau et al, ), concentrated in an island of less than 450 ha. Thus, in Zembra, competition for finding a breeding site within the colony may be stronger than in other colonies and individuals may have a greater pressure to migrate earlier in their prebreeding movements than individuals from any other colony (Sparks et al, ).…”

Section: Discussionmentioning

confidence: 97%

“…A Scopoli's shearwater ( Calonectris diomedea ) sampled in this study inside its burrow in the colony of Zembra Island, Tunisia. The population size of this colony is the largest throughout the Mediterranean Basin, and hosts more than 75% of the world's breeding population of the species with more than 140,000 breeding pairs (Defos du Rau et al, ). Photograph by Raül Ramos…”

Section: Introductionmentioning

confidence: 99%

“…From what was known from previous studies, I would expected that different populations of adult Scopoli's shearwaters concentrate around SoG, still in the Mediterranean, and cross it massively and within a few days during their autumn passage F I G U R E 1 A Scopoli's shearwater (Calonectris diomedea) sampled in this study inside its burrow in the colony of Zembra Island, Tunisia. The population size of this colony is the largest throughout the Mediterranean Basin, and hosts more than 75% of the world's breeding population of the species with more than 140,000 breeding pairs (Defos du Rau et al, 2015). Photograph by Raül Ramos Tellería, 1980).…”

Section: Introductionmentioning

confidence: 99%

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Crossing the Pillars of Hercules: Understanding transoceanic migrations of seabirds throughout their breeding range

Ramos

2019

Ecology and Evolution

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Variability in long‐distance migration strategies is still poorly understood due to the fact that individuals are often tracked from a single colony/population. Transoceanic migrations of Scopoli's shearwaters ( Calonectris diomedea ) across the Strait of Gibraltar (SoG) have been tracked from several breeding colonies isolatedly, and factors related to the variability in phenological schedules among different populations remain, therefore, not well‐understood. Using light‐level geolocator data, I examined the autumn (postbreeding) and spring (prebreeding) migratory passage dates through SoG of four populations of Scopoli's shearwater spread along the longitudinal breeding range of the species. Additionally, I also estimated the at‐sea activity patterns (from immersion data) during both migratory passages, as well as the body size (from morphometric data) of the individuals of these populations. On average, Scopoli's shearwaters leave the Mediterranean (cross SoG) on 31 October ± 1.8 days on their autumn migrations and return on 03 March ± 1.6 days on their spring migrations. At the population level, there was a clear gradient in the timing of crossing SoG: birds from the westernmost populations (Murcia, SE Spain) were the first ones in leaving the Mediterranean while easternmost breeders (Paximada, Crete) were the last ones. In spring, only birds from the largest breeding population (Zembra, Tunisia) seemed to advance their return and crossed SoG significantly earlier than birds tracked at the remaining populations. In both passages, shearwaters from central and eastern populations spent more time flying than their conspecifics from the western Mediterranean. Scopoli's shearwater populations display a differential phenology and behavior in their migratory passages through SoG. The longitudinal gradient in body size already reported for the species could be an evolutionary response to an obvious trade‐off between sharing common wintering grounds in the Atlantic Ocean and the temporal constraints of restoring physiological condition in those grounds. OPEN RESEARCH BADGES This article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://hdl.handle.net/2445/128784 .

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Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Crossing the Pillars of Hercules: Understanding transoceanic migrations of seabirds throughout their breeding range

Ramos

2019

Ecology and Evolution

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“…; Defos du Rau et al . ); and here we estimate population size of shearwaters by capture–recapture of chicks in and outside nests (see details in Appendix S1). Our approach to estimate proportion of monitored nests (β) can be used in other species in which fledglings/juveniles wander far from their nests (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…However, this type of information can be obtained or estimated by other methods alternative to the individual capture-markrecapture programs on fixed breeding sites (Williams, Nichols & Conroy 2002;Thomas et al 2010). For example, Cannell et al (2011) combined count at beaches and capture-mark-recapture to estimate the population size of little penguins Eudyptula minor; a distance sampling procedure was used to estimate the number of breeding pairs at the world' largest colony of Scopoli's shearwater (Thomas et al 2010;Defos du Rau et al 2015); and here we estimate population size of shearwaters by capture-recapture of chicks in and outside nests (see details in Appendix S1). Our approach to estimate proportion of monitored nests (b) can be used in other species in which fledglings/juveniles wander far from their nests (e.g.…”

Section: O D E L L I M I T a T I O N Smentioning

confidence: 99%

Estimating recruitment and survival in partially monitored populations

Sanz‐Aguilar

Igual

Oró

et al. 2015

Journal of Applied Ecology

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Summary1. In evolutionary and ecological studies, demographic parameters are commonly derived from detailed information collected on a limited number of individuals or in a confined sector of the breeding area. This partial monitoring is expected to underestimate survival and recruitment processes because individuals marked in a monitored location may move to or recruit in an unobservable site. 2. We formulate a multi-event capture-recapture model using E-SURGE software which incorporates additional information on breeding dispersal and the proportion of monitored sites to obtain unbiased estimates of survival and recruitment rates. Using simulated data, we assessed the biases in recruitment, survival and population growth rate when monitoring 10-90% of the whole population in a short-and a long-lived species with low breeding dispersal. Finally, we illustrate the approach using real data from a long-term monitoring program of a colony of Scopoli's shearwaters Calonectris diomedea. 3. We found that demographic parameters estimated without considering the proportion of the area monitored were generally underestimated. These biases caused a substantial error in the estimated population growth rate, especially when a low proportion of breeding individuals were monitored. 4. The proposed capture-recapture model successfully corrected for partial monitoring and provided robust demographic estimates. 5. Synthesis and applications. In many cases, animal breeding populations can only be monitored partially. Consequently, recruitment and immature survival are underestimated, but the extent of these biases depends on the proportion of the area that remains undetected and the degree of breeding dispersal. We present a new method to obtain robust and unbiased measures of survival and recruitment processes from capture-recapture data. The method can be applied to any monitored population regardless of the type of nests (e.g. artificial or natural) or breeding system (e.g. colonial or territorial animals), and it only relies on an estimate of the proportion of the monitored area. The unbiased estimates obtained by this method can be used to improve the reliability of predictions of demographic population models for species' conservation and management.

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Uncertainty in population estimates: A meta‐analysis for petrels

Bird

Woodworth

Fuller

et al. 2021

Ecol Sol and Evidence

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1. Population estimates are commonly generated and used in conservation science.All estimates carry inherent uncertainty, but little attention has been given to when and how this uncertainty limits their use. This requires an understanding of the specific purposes for which population estimates are intended, an assessment of the level of uncertainty each purpose can tolerate, and information on current uncertainty.2. We conducted a review and meta-analysis for a widespread group of seabirds, the petrels, to better understand how and why population estimates are being used.Globally petrels are highly threatened, and aspects of their ecology make them difficult to survey, introducing high levels of uncertainty into population estimates.3. We found that by far the most common intended use of population estimates was to inform status and trend assessments, while less common uses were trialling methods to improve estimates and assessing threat impacts and conservation outcomes.4. The mean coefficient of variation for published estimates was 0.17 (SD = 0.14), with no evidence that uncertainty has been reduced through time. As a consequence of this high uncertainty, when we simulated declines equivalent to thresholds commonly used to trigger management, only 5% of studies could detect significant differences between population estimates collected 10 years apart for populations declining at a rate of 30% over three generations. Reporting of uncertainty was variable with no dispersion statistics reported with38% of population estimates and most not reporting key underlying parameters: nest numbers/density and nest occupancy. We also found no correlation between uncertainty in petrel population estimates and either island size, body size or species threat status -potential predictors of uncertainty. 6. Key recommendations for managers are to be mindful of uncertainty in past population estimates if aiming to collect contemporary estimates for comparison, to report uncertainty clearly for new estimates, and to give careful consideration to whether a proposed estimate is likely to achieve the requisite level of certainty for the This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Reassessment of the size of the Scopoli’s Shearwater population at its main breeding site resulted in a tenfold increase: implications for the species conservation

Cited by 19 publications

References 33 publications

Crossing the Pillars of Hercules: Understanding transoceanic migrations of seabirds throughout their breeding range

Crossing the Pillars of Hercules: Understanding transoceanic migrations of seabirds throughout their breeding range

Estimating recruitment and survival in partially monitored populations

Uncertainty in population estimates: A meta‐analysis for petrels

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