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Les articles de Timothée Schwartz
de Timothée Schwartz, Aurélien Besnard, Christophe Pin, Olivier Scher, Thomas Blanchon, Arnaud Béchet, Nicolas Sadoul
In Conservation Biology, Online (September, 2022)
En ligne : onlinelibrary.wiley.com[...]
By rapidly modifying key habitat components, habitat restoration is at risk of producing attractive cues for animals without providing habitats of sufficient quality. As such, individual fitness components such as reproduction could be reduced and restored habitats could become ecological traps. This risk notably appears by using artificial constructions in restoration projects, yet few studies have evaluated their efficacy in a robust way. In this study, we investigated this by analysing 154 islets that were created or restored in order to improve the conservation status of seven colonial Laridae species in the south of France. During a 10-year study period (2007 to 2016), we compared occupancy dynamics and breeding parameters of these species between the restored sites and 846 unmanaged nesting sites. We also explored species’ preference for different nesting site characteristics and their respective effect on breeding parameters. We found that restored nesting sites were more attractive than unmanaged sites for all species except the black-headed gull. Colonization probability was higher in sites already used by other species the previous year. Abandonment probability was lower when breeding was successful the previous year in all species except the Sandwich tern, and decreased with the size of the colony the previous year in four of the seven species. Breeding parameters were significantly higher on managed sites. Distance from the shore was an important attractive characteristic of artificial nesting sites in all species. Other nesting site characteristics had species-specific effects on colonization, abandonment and breeding success. These results indicate that managed nesting sites are successful conservation tools for colonial Laridae in the Mediterranean and do not act as ecological traps. Our study shows that the test of the ecological trap hypothesis is a robust way to evaluate the success of restoration projects of breeding habitats.
de Timothée Schwartz, Aurélien Besnard, Jesus M. Aviles, Teresa Catry, Andrzej Gorski, Orsolya Kiss, Deseada Parejo, Edmunds Račinskis, Laimonas Sniauksta, Milda Šniaukštienė, et al.
In Oecologia, 197 (August, 2021), 167–178
En ligne : doi.org[...]
Life-history theory predicts that animals should develop adaptive trade-offs between survival and reproduction to maximize their fitness. This results in a continuum of life-history strategies among species, ranging from slow to fast paces-of-life. The optimal pace-of-life has been shown to vary within environmental gradients, with a commonly observed pattern of a slow-to-fast continuum from the tropics to the poles. Within species, pace-of-life variability has however received much less attention. In this study, we investigated whether or not the pace-of-life of populations within a species follows the expected slow–fast continuum associated with latitude. We analysed the variability of life-history strategies among populations of the European roller Coracias garrulus, a long-distance migratory species, comparing breeding parameters and adult survival between populations across a latitudinal gradient. The findings showed a negative correlation between survival and clutch size in roller populations, with a slower pace-of-life in the northern populations and a faster pace-of-life in the southern populations: a reverse gradient to what might be expected from inter-specific studies. These results suggest that northern populations would benefit from measures enhancing adult survival probability, such as reduction in harvesting rates, while southern populations would respond better to actions favouring reproductive success, such as nesting site provisioning. This study highlights that life-history traits can vary substantially between populations of a single species with a large latitudinal breeding range, and pinpoint how knowledge about this variability may be key in anticipating different populations’ responses to threats as well as to conservation strategies.
de Timothée Schwartz, Arnaud Genouville, Aurélien Besnard
In Ecology and Evolution, 10(24) (December, 2020), 13649-13663
En ligne : onlinelibrary.wiley.com[...]
Artificial devices are increasingly used in conservation measures to mitigate the disappearance of natural habitats. However, few studies have demonstrated their benefits for the target species, and they may pose a risk of creating ecological traps. This occurs when lower individual fitness is found in artificial habitats that are more attractive than their natural equivalents. In this study, we tested the ecological trap hypothesis on a dense population of European rollers Coracias garrulus breeding in both natural cavities and nest boxes. Our initial prediction was that the more stressful microclimatic conditions of nest boxes would lead to reduced fitness of European rollers, thus creating an ecological trap. The results showed that nest boxes were preferred over natural cavities. Despite significantly more extreme microclimatic conditions in nest boxes, we found similar breeding parameters between artificial and natural nest types. Our results also suggest that European rollers selected the nest boxes which best buffered the temperature, thus avoiding potential ecological traps. Overall our results led to the conclusion that nest boxes do not create ecological traps for European rollers in this study area. However, other species may be more sensitive to microclimatic variations or less able to avoid the least favorable nest boxes. These findings could help to inform the placement of nest boxes in order to reduce extreme temperatures and variation in humidity rates. Future studies could compare nest types for other fitness parameters, such as juvenile body condition or survival. We also recommend the ecological trap hypothesis as a useful framework to evaluate the outcomes of artificial devices used for conservation.Geographic variation in body size among French populations of the European pond turtle
de Fabien Mignet, Jean-Yves Barnagaud, Laurent Barthe, Albert Bertolero, Valerie Bosc, Florine Escot, Romain Fleuriau, Laurent Joubert, André Joyeux, Damien Lerat, et al.
In Amphibia-Reptilia, 42(2) (October, 2020), 1-11
En ligne : brill.com[...]
The processes underlying macroecological gradients in body size are widely debated, in part because their intraspecific variability remains poorly described even in well-studied taxa such as vertebrates. In this study, we investigated how climate, habitat, genetic lineage and sex explain body size variations in French populations of the European pond turtle (Emys orbicularis). We measured 7016 adult individuals captured in 41 populations, covering most of the species’ distribution in metropolitan France, including Corsica. Body size variation in our sample was wide and comparable to that found across the species’ worldwide range. Variation was similar in magnitude at regional and local levels, suggesting that body size is influenced by local factors as much as by regional factors such as climate or genetic lineage. Smaller sizes were associated with Mediterranean or altered oceanic climates, and with two lineages (E. o. galloitalica and E. o. galloitalica/E. o. orbicularis), while larger sizes were associated with northern environments and the orbicularis lineage. Body size variations recorded at local level reflect an adaptive response to environmental constraints, suggesting that habitat is also an important factor in understanding size variation.
de Orsolya Kiss, Ines Catry, Jesus M. Aviles, Sanja Barisic, Tatiana Kuzmenko, Svilen Cheshmedzhiev, Ana Teresa Marques, Angelo Meschini, Timothée Schwartz, Béla Tokody, et al.
In Bird Study, 67(2) (July, 2020), 1-17
En ligne : www.tandfonline.com[...]
We used MaxEnt for species distribution modelling based on the reconstructed distribution map of the species.
Our results suggest that during glacial periods Rollers persisted in small southern refugia, and then spread and colonized northern latitudes during the mid-Holocene. In the future, our models forecast a shift in climatically suitable range towards northern latitudes and an overall small range contraction (4.5–5.5%). Warmer temperatures will increase climate suitability in northern countries where the species is currently declining or became locally extinct. On the other hand, wide suitable areas under current climatic conditions are predicted to become unsuitable in the future (35–38% by 2050 and 2070, respectively), significantly impacting large populations such as those in Romania, Spain, Bulgaria and Hungary. French and Italian populations are identified to be future key populations for Roller conservation.
Our findings suggest that future climate changes will likely amplify the impacts of existing threats on the majority of large European Roller populations in Europe.
de Timothée Schwartz
Paris : Université Paris sciences et lettres, 2020, 308
En ligne : www.theses.fr[...]
Les activités humaines sont à l'origine des changements environnementaux actuels et de la crise d'extinction d'espèces qui en découle. Pour y faire face, de nombreuses politiques publiques de protection de la nature ont été mises en place au cours du dernier siècle. L'évaluation environnementale en particulier est apparue dans les années 70 afin de pouvoir éviter, réduire et compenser les impacts des projets de développement et d'infrastructures sur l'environnement, mais les mesures compensatoires qui en découlent font largement appel à l'intervention directe de l'Homme. Au-delà des questions éthiques qu'ils soulèvent, il est possible que les habitats ainsi créés ou restaurés par l'Homme se révèlent défavorables à la survie ou à la reproduction des individus qu'ils attirent, et qu'ils soient donc au final contreproductifs, devenant ce que l'on appelle des pièges écologiques. Ce risque est particulièrement grand pour les dispositifs artificiels, comme les nichoirs et autres gîtes à destination des vertébrés. Vu l'engouement que ces dispositifs suscitent, il est aujourd'hui crucial d'évaluer leur impact réel sur les populations ciblées. Il est aussi urgent de produire des recommandations pour leur utilisation optimale dans une optique de conservation des espèces visées par ces dispositifs. Cette thèse aura donc pour but d'évaluer la pertinence d'un certain nombre de dispositifs artificiels de conservation des vertébrés utilisés actuellement pour la conservation des espèces et notamment dans le cadre de la compensation écologique. Elle s'intéressera en particulier aux gîtes artificiels qui sont très utilisés dans ces contextes. Pour ce faire, nous chercherons tout d'abord à évaluer dans quelle mesure ces dispositifs peuvent constituer des pièges écologiques, en particulier en les comparant à leurs équivalents naturels. Nous comparerons d'une part la dynamique de colonisation et d'abandon entre différents types de sites (artificiels ou non), et d'autre part l'impact de ces dispositifs sur la survie et la reproduction des individus qui les utilisent. Dans un deuxième temps, nous travaillerons à identifier les causes de l'impact négatif de ces dispositifs, le cas échéant, afin de formuler des recommandations de bonnes pratiques pour leur utilisation. Pour cela nous nous intéresserons aux facteurs d'origine humaine : détectabilité des dispositifs, positionnement spatial par rapport aux habitats d'alimentation, caractéristiques physiques et structurelles et microclimat dans les gîtes. Nous étudierons également les stratégies d'évitement des pièges écologiques par les espèces utilisant ces dispositifs et nous mènerons une étude totalement inédite sur l'impact du type de nid sur le microbiote des rolliers. Notre principal modèle d'étude sera le rollier d'Europe Coracias garrulus étudié par l'association A Rocha France depuis plus de quinze ans. Nous nous intéresserons également à trois groupes de vertébrés qui utilisent des dispositifs artificiels : un reptile (le lézard ocellé), un cortège de mammifères (les chauves-souris) et un cortège d'oiseaux d'eau (les laro-limicoles coloniaux).
Context-dependent conservation of the cavity-nesting European Roller
de Tom Finch, Claire Branston, Harriet Clewlow, Jamie Dunning, Aldina M. A. Franco, Edmunds Račinskis, Timothée Schwartz, Simon J. Butler
In Ibis, 161(3) (July 2018), 1-17
En ligne : onlinelibrary.wiley.com[...]
To maximize the effectiveness of conservation interventions, it is crucial to have an understanding of how intraspecific variation determines the relative importance of potential limiting factors. For bird populations, limiting factors include nest-site availability and foraging resources, with the former often addressed through the provision of artificial nestboxes. However, the effectiveness of artificial nestboxes depends on the relative importance of nest-site vs. foraging resource limitations. Here, we investigate factors driving variation in breeding density, nestbox occupation and productivity in two contrasting study populations of the European Roller Coracias garrulus, an obligate cavity-nesting insectivorous bird. Breeding density was more than four times higher at the French study site than at the Latvian site, and there was a positive correlation between breeding density (at the 1-km2 scale) and nest-site availability in France, whereas there was a positive correlation between breeding density and foraging resource availability in Latvia. Similarly, the probability of a nestbox being occupied increased with predicted foraging resource availability in Latvia but not in France. We detected no positive effect of foraging resource availability on productivity at either site, with most variation in breeding success driven by temporal effects: a seasonal decline in France and strong interannual fluctuations in Latvia. Our results indicate that the factors limiting local breeding density can vary across a species' range, resulting in different conservation priorities. Nestbox provisioning is a sufficient short-term conservation solution at our French study site, where foraging resources are typically abundant, but in Latvia the restoration of foraging habitat may be more important.
