Showing papers by "Vincent Bretagnolle published in 2012"

Analyzing the Design Process of Farming Practices Ensuring Little Bustard Conservation: Lessons for Collective Landscape Management

Abstract: Effective solutions for integrating development of agriculture and conservation of biodiversity at a landscape scale remain to be identified. This article presents a case study on an intensively farmed French cereal plain, where the reintroduction of grasslands has been proposed to protect the Little Bustard, a threatened European bird species. Although this solution may seem trivial at first glance, we analyze the design reasoning from which it resulted in order to highlight the innovative paths it opened. We apply C-K theory, a design theory that distinguishes concepts (i.e., unknown proposals) from knowledge. Our analysis reveals the links between the production of scientific knowledge and the generation of various solutions. It also highlights that specifying the ecological functions of grasslands facilitates their management. In the cereal plain, some of these functions give grasslands the status of common goods. This consideration opens new possibilities for managing agricultural landscapes in a way...

Vegetation height and egg coloration differentially affect predation rate and overheating risk: an experimental test mimicking a ground-nesting bird

Abstract: Avian eggs need to be laid in protected environments to develop and survive. Nest predation is known as the main cause of breeding failure for many birds, but nest microclimate conditions are also ...

Centaurea cyanus as a biological indicator of segetal species richness in arable fields

Abstract: Bellanger S, Guillemin J-P, Bretagnolle V & Darmency H (2012). Centaurea cyanus as a biological indicator of segetal species richness in arable fields. Weed Research52, 551–563. Summary Agricultural intensification has resulted in a loss of biological diversity within European agroecosystems. Biological indicator species are important tools for monitoring species diversity. The aim of this study was to determine whether cornflower, Centaurea cyanus, an arable land specialist segetal species that is easily identified in the countryside, is an appropriate indicator of weed species diversity in the Poitou-Charentes region of western France. The study zones selected were those in which C. cyanus was present in agricultural fields when monitoring was conducted in both 2006 and 2007. All plant species in sample fields sown with winter crops (cereals and oilseed rape) within the study zones were then inventoried in two consecutive years: 2008 and 2009. For these winter crops, C. cyanus presence was not a good indicator of overall species richness within the fields. However, C. cyanus presence did correlate with the presence of other arable land specialists, herein called segetal species. Reciprocally, the presence of most other segetal species found at low frequencies in the study zones also correlated with higher segetal richness. We discuss the conditions for using C. cyanus as an indicator of segetal diversity with regards to conservation and ecosystem services.

The complete phylogeny of Pseudobulweria, the most endangered seabird genus: systematics, species status and conservation implications

Abstract: Pseudobulweria is one of the least known and most endangered of all seabird genera. It comprises six taxa, of which two are extinct, three are critically endangered and one is near threatened. Phylogenetic relationships between these taxa and position of the genus in the Order Procellariiformes have never been studied, and the taxonomic status of several taxa remains unsettled. Conservation management of Pseudobulweria taxa will be enhanced if these uncertainties are resolved. We used a multilocus gene tree approach with two mitochondrial DNA markers (cytochrome oxidase subunit 1 and cytochrome b gene) and one nuclear intron (β Fibrinogen intron 7) to investigate phylogenetic relationships within the genus using sequences from all taxa. We combined gene trees to estimate a phylogeny of the genus using a multispecies coalescent methodology. We confirmed the link between Pseudobulweria and a clade comprising Puffinus and Bulweria genera. The Fiji petrel’s status, as belonging to the genus, is confirmed, as is the specific status of newly rediscovered Beck’s petrel. Maintenance of the two sub-species of Tahiti petrel as currently described is not supported. Discovering the breeding grounds of all taxa is the key for their conservation, which is vital to both the marine and fragile insular tropical ecosystems where Pseudobulweria are apical predators.

Carotenoid-Based Coloration, Condition, and Immune Responsiveness in the Nestlings of a Sexually Dimorphic Bird of Prey

Abstract: In many birds, nestlings exhibit brightly colored traits that are pigmented by carotenoids. Carotenoids are diet limited and also serve important health-related physiological functions. The proximate mechanisms behind the expression of these carotenoid-pigmented traits are still poorly known, especially in nestlings with sexual size dimorphism. In these nestlings, intrabrood competition levels and growth strategies likely differ between sexes, and this may in turn influence carotenoid allocation rules. We used dietary carotenoid supplementation to test whether wild marsh harrier (Circus aeruginosus) nestlings were carotenoid limited and whether carotenoid allocation strategies varied between sexes, which differ in their size and growth strategies. When supplemented, nestlings used the supplemental carotenoids to increase their coloration independently of their sex. We showed that the condition dependence of the carotenoid level and the response to an immune challenge (phytohemagglutinin test) diff...

Carotenoid limitation and allocation priorities in asynchronous raptor nestlings

Abstract: The evolution and maintenance of conspicuous animal traits and communication signals have long fascinated biologists. Many yellow–red conspicuous traits are coloured by carotenoid pigments, and in some species they are displayed at a very young age. In nestling birds, the functions and proximate mechanisms of carotenoid-pigmented traits are probably different and not as well known as those of adults. Here we investigated how Montagu’s harrier (Circus pygargus) nestlings within structured families used a limited resource, carotenoid pigments, and whether they used these for increasing coloration (deposition in integuments) or for mounting a response to a phytohaemagglutinin (PHA) challenge, which measures pro-inflammatory potential and aspects of cellular immune responsiveness. We manipulated carotenoid availability, using dietary carotenoid supplementations, and show that when supplemented, nestlings primarily allocated supplemental carotenoids to increase their coloration, irrespective of their sex, but depending of their position within the brood. Responses to PHA challenge were condition-dependent, but depending on carotenoid availability. Moreover, how nestlings allocated carotenoids depended on their rank within the brood, which in turn influenced their level of carotenoid limitation (first-hatched nestlings being less constrained than later-hatched nestlings). We discuss why nestlings would use supplemental carotenoids for increasing bare parts coloration rather than for responding to a PHA challenge, and the potential benefits for doing so in a parent–offspring communication context. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 13–24.

Adaptive significance of permanent female mimicry in a bird of prey

Abstract: Permanent female mimicry, in which adult males express a female phenotype, is known only from two bird species. A likely benefit of female mimicry is reduced intrasexual competition, allowing female-like males to access breeding resources while avoiding costly fights with typical territorial males. We tested this hypothesis in a population of marsh harriers Circus aeruginosus in which approximately 40 per cent of sexually mature males exhibit a permanent, i.e. lifelong, female plumage phenotype. Using simulated territorial intrusions, we measured aggressive responses of breeding males towards conspecific decoys of females, female-like males and typical males. We show that aggressive responses varied with both the type of decoys and the type of defending male. Typical males were aggressive towards typical male decoys more than they were towards female-like male decoys; female-like male decoys were attacked at a rate similar to that of female decoys. By contrast, female-like males tolerated male decoys (both typical and female-like) and directed their aggression towards female decoys. Thus, agonistic responses were intrasexual in typical males but intersexual in female-like males, indicating that the latter not only look like females but also behave like them when defending breeding resources. When intrasexual aggression is high, permanent female mimicry is arguably adaptive and could be seen as a permanent ‘non-aggression pact’ with other males.

Spatial Autocorrelation in Farmland Grasshopper Assemblages (Orthoptera: Acrididae) in Western France

Abstract: Agricultural intensification in western Europe has caused a dramatic loss of grassland surfaces in farmlands, which have resulted in strong declines in grassland invertebrates, leading to cascade effects at higher trophic levels among consumers of invertebrates. Grasshoppers are important components of grassland invertebrate assemblages in European agricultural ecosystems, particularly as prey for bird species. Understanding how grasshopper populations are distributed in fragmented landscapes with low grassland availability is critical for both studies in biodiversity conservation and insect management. We assessed the range and strength of spatial autocorrelation for two grasshopper taxa (Gomphocerinae subfamily and Calliptamus italicus L.) across an intensive farmland in western France. Data from surveys carried out over 8 yr in 1,715 grassland fields were analyzed using geostatistics. Weak spatial patterns were observed at small spatial scales, suggesting important local effects of management practices on grasshopper densities. Spatial autocorrelation patterns for both grasshopper taxa were only detected at intermediate scales. For Gomphocerinae, the range of spatial autocorrelation varied from 802 to 2,613 m according to the year, depending both on grasshopper density and on grassland surfaces in the study site, whereas spatial patterns for the Italian locust were more variable and not related to grasshopper density or grassland surfaces. Spatial patterns in the distribution of Gomphocerinae supported our hypothesis that habitat availability was a major driver of grasshopper distribution in the landscape, and suggested it was related to density-dependent processes such as dispersal.

Group size modulates time budget and foraging efficiency in captive Skylarks, Alauda arvensis

Abstract: Skylarks (Alauda arvensis) are known to adopt a typical aggregative behaviour during the wintering period. A further benefit is that individuals in larger groups can decrease the amount of time they spent being vigilant, while maintaining a high probability of predator detection. Using wild birds temporarily housed in outdoor aviaries, we investigated the influence of group size (1, 2 and 4 individuals) on individual time budget (vigilance vs. foraging), and the pecking (number of pecks) and intake rates (number of seeds consumed). Results showed that individuals reduced their vigilance and increased their pecking rate when group size increased. However, the intake rate was not maximised in the largest group suggesting that large flocks would negatively affect individual foraging efficiency. A consideration of the whole set of costs and benefits will be necessary before the adaptive value of group living in any species can be fully assessed.

Large-scale geographic variation in iridescent structural ornaments of a long-distance migratory bird

Abstract: Iridescent colours produced during moult likely play an important role in pair formation in birds. We sought to quantify geographic variation in such colouration in a duck species, Eurasian teal Anas crecca , in winter (when mating occurs) to evaluate whether this variation refl ects birds ' breeding origins or diff erential individual migration strategies in both males and females. We combined information on feather production region and individual attributes (body size, sex and age) of Eurasian teal from 82 wintering sites in France. Feather production region (moult site or natal origin) was inferred using feather deuterium values ( δ D f ). We performed spectral measurements to evaluate speculum colour and brightness contrasts for 1052 teal collected over four years. Colouration diff ered strongly among wintering regions, with birds wintering in eastern France exhibiting higher colour contrast than those wintering in the west. Body size and colouration were positively related. Th ere were no diff erences in cohort-specifi c δ D f values between separate wintering regions in France, indicating that within a winter quarter teal originated from areas across the entire breeding range. Overall, patterns of spatial variation in feather colouration were related most closely to body size which was consistent with predictions of a diff erential migration hypothesis, with larger and more colour-contrasting birds wintering closer to their breeding grounds. Because moult speed is also known to aff ect colour production, early breeders or individuals that skipped reproduction may have invested more or earlier in their feather quality to gain potential advantages in monopolizing future mates.

Phenotypic variation in nestlings of a bird of prey under contrasting breeding and diet conditions

Abstract: Environmental conditions often vary in space and time, and this may explain variation in the expression of phenotypic traits related to individual quality, such as ornamental coloration. Furthermore, the direction and strength of the relationship between coloured trait expression and individual quality might vary under contrasting conditions. These issues have been explored in adult birds but much less so in nestlings, which are more likely to experience different selective pressures and different physiological trade-offs than adults. Here, we empirically investigated the effects of contrasting breeding and diet conditions on the expression of carotenoid-based colour traits displayed by marsh harrier (Circus aeruginosus) nestlings. We studied the variation in coloration, body condition, and immune responsiveness of nestlings in four populations over a 5-year period. We characterized spatiotemporal differences in rearing conditions experienced by C. aeruginosus nestlings in terms of breeding (laying date, clutch size, and number of nestlings hatched and fledged) and diet (percentage of mammal in diet and prey diversity) conditions. We found that breeding conditions influenced the co-variation between coloration and immune responsiveness in female nestlings, and that diet conditions influenced the condition-dependence of nestling coloration in later-hatched nestlings. In addition, breeding conditions influenced nestling body condition and immune responsiveness, whereas diet conditions influenced nestling coloration and body condition. Our study highlights that nestling phenotype (levels of signalling, circulating carotenoids, and immunity) varies both spatially and temporally, and that some of this variation is related to differences in breeding and diet conditions. Moreover, under contrasting conditions, the direction of the relationships between nestling carotenoid-based coloration and nestling quality may also vary. In order to fully understand the evolution and maintenance of colour traits in nestling birds, studies and experiments should ideally be replicated under contrasting rearing conditions. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ••, ••–••.

Decomposing the heterogeneity of species distributions into multiple scales: a hierarchical framework for large-scale count surveys

Abstract: We introduce a novel spatially explicit framework for decomposing species distributions into multiple scales from count data. These kinds of data are usually positively skewed, have non-normal distributions and are spatially autocorrelated. To analyse such data, we propose a hierarchical model that takes into account the observation process and explicitly deals with spatial autocorrelation. The latent variable is the product of a positive trend representing the non-constant mean of the species distribution and of a stationary positive spatial field representing the variance of the spatial density of the species distribution. Then, the different scales of emergent structures of the distribution of the population in space are modelled from the latent density of the species distribution using multi-scale variogram models. Multi-scale kriging is used to map the spatial patterns previously identified by the multi-scale models. We show how our framework yields robust and precise estimates of the relevant scales both for spatial count data simulated from well-defined models, and in a real case-study based on seabird count data (the common guillemot Uria aalge) provided by large-scale aerial surveys of the Bay of Biscay (France) performed over a winter. Our stochastic simulation study provides guidelines on the expected uncertainties of the scales estimates. Our results indicate that the spatial structure of the common guillemot can be modelled as a three-level hierarchical system composed of a very broad-scale pattern (∼ 200 km) with a stable location over time that might be environmentally controlled, a broad-scale pattern (∼ 50 km) with a variable shape and location, that might be related to shifts in prey distribution, and a fine-scale pattern (∼ 10 km) with a rather stable shape and location, that might be controlled by behavioural processes. Our framework enables the development of robust, scale-dependent hypotheses regarding the potential ecological processes that control species distributions.

Rôle des prairies temporaires pour la gestion de la flore adventice dans les systèmes céréaliers

Abstract: La complementarite entre les productions cerealieres (sensu lato) et les productions fourrageres liees a l'elevage est un levier majeur de gestion de la flore adventice, par la diversification des successions culturales qu'elle permet. Cet article synthetise les connaissances actuelles sur les effets sur la flore de l'insertion de prairies temporaires dans les successions cerealieres, sur la base d'une etude bibliographique et de travaux menes en France. Les releves de flore en parcelle agricole et les experimentations en station convergent pour demontrer l'effet precedent repressif des prairies temporaires (en particulier la luzerne) sur de nombreuses especes adventices tres problematiques dans les systemes cerealiers. Les prairies temporaires peuvent favoriser certaines especes, mais peu problematiques en grandes cultures : especes a port rampant ou en rosette, a cycle court, peu competitives, ou especes vivaces perturbees par les travaux du sol pendant les phases de la succession de cultures annuelles. Une enquete sur les pratiques des agriculteurs de la Zone Atelier " Plaine & Val de Sevre " a montre que la diversification des successions par des cultures fourrageres et des legumineuses permet de concilier la reduction de la dependance aux herbicides, la reduction desimpacts environnementaux, la reduction des consommations d'energie a l'echelle du systeme, et la rentabilite economique.

Managing grasslands biodiversity at a landscape level to foster ecosystem services in intensive cereal systems: from ecological knowledge to collective action

Abstract: Effective solutions for integrating agricultural development and conservation of biodiversity at the landscape scale remain to be identified. We present a case study in an intensively farmed French cereal plain, where the reintroduction of grasslands has been proposed first for conservation purposes in order to protect the Little Bustard, a highly threatened bird species. In these highly fragmented and disturbed habitats, the presence, abundance and distribution of grasslands therefore have a critical role in ecological and environmental regulatory processes. To restore these processes, it is critical to rationalize the inclusion of grasslands in the cropping system (in time, space and according to management practices). However, currently, grasslands are severely depleted by farmers who privilege cereal crops for economic reasons . We therefore raise the issue of whether crop allocation at the landscape scale can be changed without public funding, in order to increase the proportion of grasslands. A solution explored here is to identify the interdependencies between farmers related to the ecosystem services grasslands provide at the landscape scale. The recognition of grassland emergent functions when considered at the landscape scale gives them a status of common good: a good that should be collectively managed to maximize ecosystem services. This consideration leads to involve new stakeholders such as citizens, scientists, government bodies or NGOs in the collective management of grasslands and opens an innovative way to reconcile agriculture and conservation at the landscape scale.

Gestion de la biodiversité en milieu céréalier intensif : importance des prairies aux échelles locales et régionales

Abstract: Des solutions efficaces pour integrer le developpement agricole et la conservation de la biodiversite a l'echelle du paysage restent a identifier. Nous presentons une etude de cas dans une plaine cerealiere francaise exploitee de facon intensive, ou la reintroduction des prairies a ete propose d'abord pour des fins de conservation afin de proteger l'outarde canepetiere, une espece d'oiseau tres menacee. Les prairies ont ete mises en place grâce a l’outil « Mesures Agri-environnementales (MAE) », a titre experimental. L’efficacite des MAE sur les outardes a ete totale. Leur mise en oeuvre a revele d'autres effets benefiques sur pratiquement toutes les composantes du reseau trophique dans ces agroecosystemes, en particulier au niveau du paysage. En effet, dans les systemes cerealiers intensifs, les habitats perennes telles que les prairies sont radicalement differentes de cultures annuelles en termes de niveau et de frequence des perturbations (labour, semis, pulverisation, etc.). Nos resultats montrent que les prairies, en particulier la luzerne, sont le support de nombreux services ecosystemiques. Cependant, actuellement, les prairies sont peu utilisees par les agriculteurs qui privilegient les cultures de cereales pour des raisons economiques (y compris les subventions de la PAC). Nous soulevons la question de savoir si la repartition des cultures a l'echelle du paysage (par exemple l’introduction de prairies) peut etre modifiee sans financement public, afin d'en augmenter la proportion. En d'autres termes, comment surmonter la reticence des producteurs de cereales pour produire des cultures fourrageres.

Managing grasslands biodiversity at a landscape level to foster ecosystem services in intensive cereal systems: from ecological knowledge to collective action

Abstract: Effective solutions for integrating agricultural development and conservation of biodiversity at the landscape scale remain to be identified. We present a case study in an intensively farmed French cereal plain, where the reintroduction of grasslands has been proposed first for conservation purposes in order to protect the Little Bustard, a highly threatened bird species. In these highly fragmented and disturbed habitats, the presence, abundance and distribution of grasslands therefore have a critical role in ecological and environmental regulatory processes. To restore these processes, it is critical to rationalize the inclusion of grasslands in the cropping system (in time, space and according to management practices). However, currently, grasslands are severely depleted by farmers who privilege cereal crops for economic reasons . We therefore raise the issue of whether crop allocation at the landscape scale can be changed without public funding, in order to increase the proportion of grasslands. A solution explored here is to identify the interdependencies between farmers related to the ecosystem services grasslands provide at the landscape scale. The recognition of grassland emergent functions when considered at the landscape scale gives them a status of common good: a good that should be collectively managed to maximize ecosystem services. This consideration leads to involve new stakeholders such as citizens, scientists, government bodies or NGOs in the collective management of grasslands and opens an innovative way to reconcile agriculture and conservation at the landscape scale.

Governance challenges raised by the design of multiple ecosystem services in agricultural landscapes

Abstract: While Ecosystem services have become the subject of wide attention at the academic and political level, knowledge gaps, complexity and uncertainty make them hard to manage in practice (Seppelt at al., 2011). This presentation proposes an innovative methodological tool to help stakeholders optimize the provision of ecosystem services at a landscape scale, a relevant scale to study both collective action and ecological processes (Prager et al., 2012). We present the results of an on-going case study carried out in a cereal plain in the West of France. It focuses on a pioneering initiative of a cooperative aiming to reconcile agricultural production with environmental protection. Our group of researchers in social and ecological sciences developed a method based on one of the most recent design theories, the Concept-Knowledge theory (Hatchuel & Weil, 2009) with local stakeholders, to involve them in the collective exploration of ecosystem services. Efforts were focused on the reintroduction of grasslands in the cereal crop rotations to improve ecological regulation services (Berthet et al., in press). "Grassland" is a subject of controversy, considered as a natural habitat by ecologists vs. a forage production area by farmers. The collective design method made it possible to identify a conceptual model of grassland and to explore its potential properties, some of which were not known by stakeholders initially. Innovative farming practices were developed, not focused on trade-offs between production and conservation, but rather on the identification of new values that could be created by farmers through a renewed management of ecosystem services. This collective exploration process revealed new interdependences between stakeholders. This paper brings together ecological and managerial knowledge to develop an innovative method aimed at fostering the collective design of ecosystem services at a landscape scale. It also gives useful insights to develop ad-hoc governance strategies.