Isabelle Le Viol

More and more generalists: two decades of changes in the European avifauna.

Biotic homogenization (BH) is a process whereby some species (losers) are systematically replaced by others (winners). While this process has been related to the effects of anthropogenic activities, whether and how BH is occurring across regions and the role of native species as a driver of BH has hardly been investigated. Here, we examine the trend in the community specialization index (CSI) for 234 native species of breeding birds at 10 111 sites in six European countries from 1990 to 2008. Unlike many BH studies, CSI uses abundance information to estimate the balance between generalist and specialist species in local assemblages. We show that bird communities are more and more composed of native generalist species across regions, revealing a strong, ongoing BH process. Our result suggests a rapid and non-random change in community composition at a continental scale is occurring, most likely driven by anthropogenic activities.

Use of Large‐Scale Acoustic Monitoring to Assess Anthropogenic Pressures on Orthoptera Communities

Biodiversity monitoring at large spatial and temporal scales is greatly needed in the context of global changes. Although insects are a species-rich group and are important for ecosystem functioning, they have been largely neglected in conservation studies and policies, mainly due to technical and methodological constraints. Sound detection, a nondestructive method, is easily applied within a citizen-science framework and could be an interesting solution for insect monitoring. However, it has not yet been tested at a large scale. We assessed the value of a citizen-science program in which Orthoptera species (Tettigoniidae) were monitored acoustically along roads. We used Bayesian model-averaging analyses to test whether we could detect widely known patterns of anthropogenic effects on insects, such as the negative effects of urbanization or intensive agriculture on Orthoptera populations and communities. We also examined site-abundance correlations between years and estimated the biases in species detection to evaluate and improve the protocol. Urbanization and intensive agricultural landscapes negatively affected Orthoptera species richness, diversity, and abundance. This finding is consistent with results of previous studies of Orthoptera, vertebrates, carabids, and butterflies. The average mass of communities decreased as urbanization increased. The dispersal ability of communities increased as the percentage of agricultural land and, to a lesser extent, urban area increased. Despite changes in abundances over time, we found significant correlations between yearly abundances. We identified biases linked to the protocol (e.g., car speed or temperature) that can be accounted for ease in analyses. We argue that acoustic monitoring of Orthoptera along roads offers several advantages for assessing Orthoptera biodiversity at large spatial and temporal extents, particularly in a citizen science framework.

First description of underwater acoustic diversity in three temperate ponds

The past decade has produced an increased ecological interest in sonic environments, or soundscapes. However, despite this rise in interest and technological improvements that allow for long-term acoustic surveys in various environments, some habitats’ soundscapes remain to be explored. Ponds, and more generally freshwater habitats, are one of these acoustically unexplored environments. Here we undertook the first long term acoustic monitoring of three temperate ponds in France. By aural and visual inspection of a selection of recordings, we identified 48 different sound types, and according to the rarefaction curves we calculated, more sound types are likely present in one of the three ponds. The richness of sound types varied significantly across ponds. Surprisingly, there was no pond-to-pond daily consistency of sound type richness variation; each pond had its own daily patterns of activity. We also explored the possibility of using six acoustic diversity indices to conduct rapid biodiversity assessments in temperate ponds. We found that all indices were sensitive to the background noise as estimated through correlations with the signal-to-noise ratio (SNR). However, we determined that the AR index could be a good candidate to measure acoustic diversities using partial correlations with the SNR as a control variable. Yet, research is still required to automatically compute the SNR in order to apply this index on a large data set of recordings. The results showed that these three temperate ponds host a high level of acoustic diversity in which the soundscapes were variable not only between but also within the ponds. The sources producing this diversity of sounds and the drivers of difference in daily song type richness variation both require further investigation. Such research would yield insights into the biodiversity and ecology of temperate ponds.

Impact of urbanization and gardening practices on common butterfly communities in France

Abstract We investigated the interacting impacts of urban landscape and gardening practices on the species richness and total abundance of communities of common butterfly communities across France, using data from a nationwide monitoring scheme. We show that urbanization has a strong negative impact on butterfly richness and abundance but that at a local scale, such impact could be mitigated by gardening practices favoring nectar offer. We found few interactions among these landscape and local scale effects, indicating that butterfly‐friendly gardening practices are efficient whatever the level of surrounding urbanization. We further highlight that species being the most negatively affected by urbanization are the most sensitive to gardening practices: Garden management can thus partly counterbalance the deleterious effect of urbanization for butterfly communities. This holds a strong message for park managers and private gardeners, as gardens may act as potential refuge for butterflies when the overall landscape is largely unsuitable.

The contribution of agent-based simulations to conservation management on a Natura 2000 site.

The conservation of biodiversity today must include the participation and support of local stakeholders. Natura 2000 can be considered as a conservation system that, in its application in most EU countries, relies on the participation of local stakeholders. Our study proposes a scientific method for participatory modelling, with the aim of contributing to the conservation management of habitats and species at a Natura 2000 site (Crozon Peninsula, Bretagne, France) that is representative of in landuse changes in coastal areas. We make use of companion modelling and its associated tools (scenario-planning, GIS, multi-agent modelling and simulations) to consider possible futures through the co-construction of management scenarios and the understanding of their consequences on different indicators of biodiversity status (habitats, avifauna, flora). The maintenance of human activities as they have been carried out since the creation of the Natura 2000s zone allows the biodiversity values to remain stable. Extensive agricultural activities have been shown to be essential to this maintenance, whereas management sustained by the multiplication of conservation actions brings about variable results according to the indicators. None of the scenarios has a positive incidence on the set of indicators. However, an understanding of the modelling system and the results of the simulations allow for the refining of the selection of conservation actions in relation to the species to be preserved.

Understanding Bat-Habitat Associations and the Effects of Monitoring on Long-Term Roost Success using a Volunteer Dataset

In gregarious species, the choice of colony location is especially crucial as the costs associated with breeding near conspecifics are important and the quality of a breeding patch is known to affect individual fitness. Consequently one could expect robust decisionmaking rules regarding colony location. The conceptual framework of animal aggregation with regards to habitat selection emphasizes that the presence and success of conspecifics are cues to habitat selection. Based on this, we explored how the distribution of breeding colonies could inform us about how habitat selection operates in bats. The data set we used was provided by a volunteer network whose first aim is to advise citizens facing bats in distress or bats in their homes. The dataset contained information on the locations of 105 serotine (Eptesicus serotinus) breeding colonies in a French region primarily dominated by an agricultural landscape. The methodology used for calculating habitat availability was based on the comparison of habitats surrounding serotine colonies to habitats surrounding random points. We found that serotine bats positively select pastoral and aquatic habitats regardless of the comparison used. The strong correlation between our results and those obtained with radio-tracking or acoustic methods underlines the robustness of this spatial distribution approach. The analysis of the history of the serotine colonies over a period of nearly 20 years showed that when attics are restored by the owners without the help of the bat rescue network, the probability of a departure of colony is greater. In addition, monitoring reduces the occurrence of an unsympathetic building restoration.

Dynamics of a northern fulmar (Fulmarus glacialis) population at the southern limit of its range in Europe

In the context of global changes, defining the source–sink dynamics of populations of emblematic species, such as seabirds, within the limits of their distribution range is often crucial to optimize the priorities of surveys and conservation management, especially in protected areas. However, ringing is often not possible and only simple survey methods, such as the ‘apparently occupied sites’ method, can be utilized by managers of protected areas and threatened species. Using data collected between 1997 and 2005, we investigated the population dynamics of the northern fulmar (Fulmarus glacialis) at the southern limit of its range on the western French coast, which hosts increasing populations. Using a robust design spatial occupancy model, we estimated the proportion of occupied nests, the rates of nest colonization, nest extinction and the population growth rates of four colonies of the largest population (Ouessant Island). The estimated annual growth rate was high (average 1.049). A deterministic population dynamics model indicated that the observed rapid increase of Ouessant populations cannot be explained by their intrinsic dynamics, which suggested an important role for immigration. Different demographic scenarios provide several lines of evidence that the large northern fulmar population in this Man and Biosphere Reserve is a sink population. The strong increase in a population located at the limits of the species distributional range implies that it functions as a population sink. Inexpensive effective survey methods could allow investigation of the demographic status of seabird populations and provide relevant information for the hierarchization of conservation priorities.

Weed control method drives conservation tillage efficiency on farmland breeding birds

Abstract Crops management is known to influence biodiversity, especially conservation tillage (CT, no-till) often found as a positive method compared to conventional tillage (T, inversion of soil) but without controlling for underlying farming practices. There are many ways to perform CT, in particular concerning the control of weeds, but few studies have taken into account these methods, which could explain the lack of consensus about the effect of CT compared to T. We tested differences in breeding birds abundance between CT and T while accounting for weed control methods in oilseed rape and wheat CT fields. During the intercrop period, one CT system used a cover crop to control weeds (CTcc), the other used herbicides (CTh) and the control (T) system only used a tillage. We made CTcc/T and CTh/T comparisons by sampling bird abundance (respectively 49 CTcc/51 T and 30 CTh/33 T point counts). We show substantial differences between CTcc/T and CTh/T comparisons as we detected greater bird abundances in CTcc than T for 5 species (2.3–4.1 times more individuals) and a lower abundance in CTh than T for 2 species (2.1–2.2 times less individuals). Our results demonstrate the importance to account for system features to ensure the CT efficiency for farmland birds, declining strongly in Europe since 1980 (−55 to −67%). Results also highlight an even more negative impact of herbicides than tillage, showing that stopping tillage to intensify herbicide use is not a promising way.

Potential of bat pass duration measures for studies of bat activity

Abstract Acoustic detectors have become increasingly used by bat workers to investigate bat ecology and assess the impacts of anthropogenic pressures. Within these studies, the metric used, ‘bat activity’, is based on the number of bat passes, without considering the bat pass duration (i.e. each event of a bat detected within the range of an ultrasonic detector). We expected that bat pass duration may contain information about site quality in terms of foraging potential. Because bats are expected to have a more sinuous trajectory and slower velocity when they exhibit foraging behaviour, as opposed to commuting behaviour, we hypothesize a longer bat pass duration in favourable habitats; during seasons with important energetic demands; or during night peak activity. We used datasets from a large-scale acoustic bat survey (n = 2890 sites), with a total of 24,597 bat pass measures from 6 taxa, and performed GLMM modelling. We detected a significant effect of habitat type on bat pass duration for five taxa. Shorter bat pass durations were detected at the beginning of the night. We detected longer pass durations during the lactation period or just before hibernating, while weather conditions or ageing and wear of the detector rarely influenced bat pass duration. Bat pass duration appears to be a simple and easy measure for position calls on a gradient between commuting vs. foraging behaviour. We suggest that the traditional measure of bat activity may be weighted by bat pass duration by giving more weight to events with potentially stronger links to foraging behaviour.

Tillage and herbicide reduction mitigate the gap between conventional and organic farming effects on foraging activity of insectivorous bats

Abstract The increased use of pesticides and tillage intensification is known to negatively affect biodiversity. Changes in these agricultural practices such as herbicide and tillage reduction have variable effects among taxa, especially at the top of the trophic network including insectivorous bats. Very few studies compared the effects of agricultural practices on such taxa, and overall, only as a comparison of conventional versus organic farming without accurately accounting for underlying practices, especially in conventional where many alternatives exist. Divergent results founded in these previous studies could be driven by this lack of clarification about some unconsidered practices inside both conventional and organic systems. We simultaneously compared, over whole nights, bat activity on contiguous wheat fields of one organic and three conventional farming systems located in an intensive agricultural landscape. The studied organic fields (OT) used tillage (i.e., inversion of soil) without chemical inputs. In studied conventional fields, differences consisted of the following: tillage using few herbicides (T), conservation tillage (i.e., no inversion of soil) using few herbicides (CT), and conservation tillage using more herbicide (CTH), to control weeds. Using 64 recording sites (OT = 12; T = 21; CT = 13; CTH = 18), we sampled several sites per system placed inside the fields each night. We showed that bat activity was always higher in OT than in T systems for two (Pipistrellus kuhlii and Pipistrellus pipistrellus) of three species and for one (Pipistrellus spp.) of two genera, as well as greater species richness. The same results were found for the CT versus T system comparison. CTH system showed higher activity than T for only one genus (Pipistrellus spp.). We did not detect any differences between OT and CT systems, and CT showed higher activity than CTH system for only one species (Pipistrellus kuhlii). Activity in OT of Pipistrellus spp. was overall 3.6 and 9.3 times higher than CTH and T systems, respectively, and 6.9 times higher in CT than T systems. Our results highlight an important benefit of organic farming and contrasted effects in conventional farming. That there were no differences detected between the organic and one conventional system is a major result. This demonstrates that even if organic farming is presently difficult to implement and requires a change of economic context for farmers, considerable and easy improvements in conventional farming are attainable, while maintaining yields and approaching the ecological benefits of organic methods.