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Camera-traps have revolutionized the way ecologists monitor biodiversity and population abundances. Their full potential is however only realized when the hundreds of thousands of images collected can be rapidly classified with minimal human intervention. Machine learning approaches, and in particular deep learning methods, have allowed extraordinary progress towards this end. Trained classification models remain rare however, and for instance are only emerging for the European fauna. This can be explained by the technical expertise they require but also by the limited availability of large datasets of annotated pictures, which are key to obtaining successful recognition models. In this context, we set-up the DeepFaune initiative ( https://deepfaune.cnrs.fr ), a large-scale collaboration between dozens of partners involved in research, conservation and management of wildlife in France. The aim of DeepFaune is to aggregate individual datasets of annotated pictures to train species classification models based on convolutional neural networks, an established deeplearning approach. Here we report on our first milestone, a two-step pipeline built upon the MegaDetector algorithm for detection (discarding empty pictures and cropping the animal) and a classification model for 18 species or higher-level taxa as well as people and vehicles. The classification model achieved 92% validation accuracy and showed > 90% sensitivity and specificity for many classes. Most importantly, these performances were generally conserved when tested on an independent out-of-sample dataset. In addition, we developed a cross-platform graphical-user-interface that allows running the pipeline on images stored locally on a personal computer. In conclusion, the DeepFaune initiative provides a freely available (for non-commercial purposes) toolbox with high performance to classify the French fauna in camera-trap images.

This is the peer reviewed version of the following article: Vitasse, Y., Ursenbacher, S., Klein, G., Bohnenstengel, T., Chittaro, Y., Delestrade, A., ... Lenoir, J. (2021). Phenological and elevational shifts of plants, animals and fungi under climate change in the European Alps. Biological Reviews, 96, 1816-1835, which has been published in final form at https://doi.org/10.1111/brv.12727. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited. Mountain areas are biodiversity hotspots and provide a multitude of ecosystem services of irreplaceable socio-economic value. In the European Alps, air temperature has increased at a rate of about 0.36°C decade−1 since 1970, leading to glacier retreat and significant snowpack reduction. Due to these rapid environmental changes, this mountainous region is undergoing marked changes in spring phenology and elevational distribution of animals, plants and fungi. Long-term monitoring in the European Alps offers an excellent natural laboratory to synthetize climate-related changes in spring phenology and elevational distribution for a large array of taxonomic groups. This review assesses the climatic changes that have occurred across the European Alps during recent decades, spring phenological changes and upslope shifts of plants, animals and fungi from evidence in published papers and previously unpublished data. Our review provides evidence that spring phenology has been shifting earlier during the past four decades and distribution ranges show an upwards trend for most of the taxonomic groups for which there are sufficient data. The first observed activity of reptiles and terrestrial insects (e.g. butterflies) in spring has shifted significantly earlier, at an average rate of −5.7 and −6.0 days decade−1, respectively. By contrast, the first observed spring activity of semi-aquatic insects (e.g. dragonflies and damselflies) and amphibians, as well as the singing activity or laying dates of resident birds, show smaller non-significant trends ranging from −1.0 to +1.3 days decade−1. Leaf-out and flowering of woody and herbaceous plants showed intermediate trends with mean values of −2.4 and −2.8 days decade−1, respectively. Regarding species distribution, plants, animals and fungi (N = 2133 species) shifted the elevation of maximum abundance (optimum elevation) upslope at a similar pace (on average between +18 and +25 m decade−1) but with substantial differences among taxa. For example, the optimum elevation shifted upward by +36.2 m decade−1 for terrestrial insects and +32.7 m decade−1 for woody plants, whereas it was estimated to range between −1.0 and +11 m decade−1 for semi-aquatic insects, ferns, birds and wood-decaying fungi. The upper range limit (leading edge) of most species also shifted upslope with a rate clearly higher for animals (from +47 to +91 m decade−1) than for plants (from +17 to +40 m decade−1), except for semi-aquatic insects (−4.7 m decade−1). Although regional land-use changes could partly explain some trends, the consistent upward shift found in almost all taxa all over the Alps is likely reflecting the strong warming and the receding of snow cover that has taken place across the European Alps over recent decades. However, with the possible exception of terrestrial insects, the upward shift of organisms seems currently too slow to track the pace of isotherm shifts induced by climate warming, estimated at about +62 to +71 m decade−1 since 1970. In the light of these results, species interactions are likely to change over multiple trophic levels through phenological and spatial mismatches. This nascent research field deserves greater attention to allow us to anticipate structural and functional changes better at the ecosystem level.

The alarming decline of amphibians around the world calls for complementary studies to better understand their responses to climate change. In mountain environments, water resources linked to snowmelt play a major role in allowing amphibians to complete tadpole metamorphosis. As snow cover duration has significantly decreased since the 1970s, amphibian populations could be strongly impacted by climate warming, and even more in high elevation sites where air temperatures are increasing at a higher rate than at low elevation. In this context, we investigated common frog (Rana temporaria) breeding phenology at two different elevations and explored the threats that this species faces in a climate change context. Our objectives were to understand how environmental variables influence the timing of breeding phenology of the common frog, and explore the threats that amphibians face in the context of climate change in mountain areas. To address these questions, we collected 11 years (2009–2019) of data on egg-spawning date, tadpole development stages, snowmelt date, air temperature, rainfall and drying up of wetland pools at ∼1,300 and ∼1,900 m a.s.l. in the French Alps. We found an advancement of the egg-spawning date and snowmelt date at low elevation but a delay at high elevations for both variables. Our results demonstrated a strong positive relationship between egg-spawning date and snowmelt date at both elevations. We also observed that the risk of frost exposure increased faster at high elevation as egg-spawning date advanced than at low elevation, and that drying up of wetland pools led to tadpole mortality at the high elevation site. Within the context of climate change, egg-spawning date is expected to happen earlier in the future and eggs and tadpoles of common frogs may face higher risk of frost exposure, while wetland drying may lead to higher larval mortality. However, population dynamics studies are needed to test these hypotheses and to assess impacts at the population level. Our results highlight climate-related threats to common frog populations in mountain environments, but additional research should be conducted to forecast how climate change may benefit or harm amphibian populations, and inform conservation and land management plans in the future.

International audience; Many phenology models have been developed to explain historical trends in plant phenology and to forecast future ones. Two main types of model can be distinguished: correlative models, that statistically relate descriptors of climate to the date of occurrence of a phenological event, and process-based models that build upon explicit causal relationships determined experimentally. While process-based models are believed to provide more robust projections in novel conditions, it is still unclear whether this assertion always holds true and why. In addition, the efficiency and robustness of the two model categories have rarely been compared. Here we aimed at comparing the efficiency and the robustness of correlative and process-based phenology models with contrasting levels of complexity in both historical and future climatic conditions. Models were calibrated, validated and compared using budburst dates of five tree species across the French Alps collected during 8 years by a citizen-science program. Process-based models were less efficient, yet more robust than correlative models, even when their parameter estimates relied entirely on inverse modeling, i.e. parameter values estimated using observed budburst dates and optimization algorithms. Their robustness further slightly increased when their parameter estimates relied on forward estimation, i.e. parameter values measured experimentally. Our results therefore suggest that the robustness of process-based models comes both from the fact that they describe causal relationships and the fact that their parameters can be directly measured. Process-based models projected a reduction in the phenological cline along the elevation gradient for all species by the end of the 21st century. This was due to a delaying effect of winter warming at low elevation where conditions will move away from optimal chilling conditions that break bud dormancy vs an advancing effect of spring warming at high elevation where optimal chilling conditions for dormancy release will persist even under the most pessimistic emissions scenario RCP 8.5. These results advocate for increasing efforts in developing process-based phenology models as well as forward modelling, in order to provide accurate projections in future climatic conditions.

Temperatures in mountain areas are increasing at a higher rate than the Northern Hemisphere land average, but how fauna may respond, in particular in terms of phenology, remains poorly understood. The aim of this study was to assess how elevation could modify the relationships between climate variability (air temperature and snow melt‐out date), the timing of plant phenology and egg‐laying date of the coal tit (Periparus ater). We collected 9 years (2011–2019) of data on egg‐laying date, spring air temperature, snow melt‐out date, and larch budburst date at two elevations (~1,300 m and ~1,900 m asl) on a slope located in the Mont‐Blanc Massif in the French Alps. We found that at low elevation, larch budburst date had a direct influence on egg‐laying date, while at high‐altitude snow melt‐out date was the limiting factor. At both elevations, air temperature had a similar effect on egg‐laying date, but was a poorer predictor than larch budburst or snowmelt date. Our results shed light on proximate drivers of breeding phenology responses to interannual climate variability in mountain areas and suggest that factors directly influencing species phenology vary at different elevations. Predicting the future responses of species in a climate change context will require testing the transferability of models and accounting for nonstationary relationships between environmental predictors and the timing of phenological events., Our study focuses on how the environmental predictors (air temperature, snow melt‐out date, and plant phenology) of breeding phenology (egg‐laying date) differ with elevation in a common woodland bird species, the coal tit.

This is a post-peer-review, pre-copyedit version of an article published in International Journal of Biometeorology. The final authenticated version is available online at: http://dx.doi.org/https://doi.org/10.1007/s00484-018-1636-x. Quantifying shifts in plant phenology in response to climate change represents an ongoing challenge, particularly in mountain ecosystems. Because climate change and phenological responses vary in space and time, we need long-term observations collected at a broad spatial scale. While data collection by volunteers is a promising approach to achieve this goal, one major concern with citizen science programs is the quality and reliability of data. Using a citizen science program (Phenoclim) carried out in the western European Alps, the goals of this study were to analyze (1) factors influencing participant retention rates, (2) the efficacy of a citizen science program for detecting temporal changes in the phenology of mountain trees, (3) differences in budburst date trends among different observer categories, and (4) the precision of trends quantified by different categories of participants. We used 12years of annual tree phenology measurements recorded by volunteers (schools and private individuals) and professionals within the Phenoclim program. We found decadal-scale shifts in budburst date consistent with the results from other studies, including significant advances in budburst date for the common birch and European ash (-4.0 and -6.5days per decade respectively). In addition, for three of six species, volunteers and professionals detected consistent directional trends. Finally, we show how differences in precision among the categories of participants are determined by the number of years of participation in the program, the number of sites surveyed, and the variability in trends among sites. Overall, our results suggest that participants with a wide range of backgrounds are capable of collecting data that can significantly contribute to the study of the impacts of climate change on mountain plant phenology.

Mountain regions are particularly susceptible and influenced by the effects of climate change. In the Alps, temperature increased two times faster than in the Northern Hemisphere during the 20th century. As an immediate response in certain tree species, spring phenological phases, such as budburst and flowering, have tended to occur earlier. However, recent studies have shown a slowing down of phenological shifts during the last two decades compared to earlier periods, which might be caused by warmer winters. Indeed, cold temperatures are required to break bud dormancy that occurs in early fall; and dormancy break is a prerequisite for cell elongation to take place in spring when temperature conditions are warm enough. Here we aimed at evaluating the effects of winter warming vs. spring warming on the phonological shift along mountain elevation gradients. We tested the hypothesis that a lack of chilling temperature during winter delayed dormancy release and subsequently spring phonological phases. For this, we used eight years of temperature and phenological records for five tree species (Betula penctula, Fraxinus excelsior, Corylus avellana, Picea abies and Larix deridna) gathered with the citizen science program Phenoclim (www.phenoclim.org) deployed over the French Alps. Our results showed that for similar preseason (i.e. after dormancy break) temperatures, warmer winters significantly delayed budburst and flowering along the elevation gradient (+ 0.9 to + 5.6 days degrees C-1) except for flowering of Corylus and budburst of Picea. For similar cold winter temperatures, warmer preseasons significantly advanced budburst and flowering along the elevation gradient (- 5.3 to -8.4 days degrees C-1). On average, the effect of winter warming was 2.3 times lower than the effect of spring warming. We also showed that warmer winter temperature conditions have a significantly larger effect at lower elevations. As a consequence, the observed delaying effect of winter warming might be beneficial to trees by reducing the risk of exposure to late spring frost on a short term. This could further lead to partial dormancy break at lower elevations before the end of the 21st century, which, in turn, may alter bud development and flowering and so tree fitness.

Aim To incorporate changes in alpine land cover (tree line shift, glacier retreat and primary succession) into species distribution model (SDM) predictions for a selection of 31 high-elevation plants. Location Chamonix Valley, French Alps. Methods We fit linear mixed effects (LME) models to historical changes in forest and glacier cover and projected these trends forward to align with 21st century IPCC climate scenarios. We used a logistic function to model the probability of plant establishment in glacial forelands zones expected to become ice free between 2008 and 2051–2080. Habitat filtering consisted of intersecting land cover maps with climate-driven SDMs to refine habitat suitability predictions. SDM outputs for tree, heath and alpine species were compared based on whether habitat filtering during the prediction period was carried out using present-day (static) land cover, future (dynamic) land cover filters or no land cover filter (unfiltered). Species range change (SRC) was used to measure differences in habitat suitability predictions across methods. Results LME predictions for 2021–2080 showed continued glacier retreat, tree line rise and primary succession in glacier forelands. SRC was highest in the unfiltered scenario (−10%), intermediate in the dynamic scenario (−15%) and lowest in the static scenario (−31%). Tree species were the only group predicted to gain overall range by 2051–2080. Although alpine plants lost range in all three land cover scenarios, new habitat made available by glacier retreat in the dynamic land cover scenario buffered alpine plant range loss due to climate change. Main conclusions We provide a framework for combining trajectories of land cover change with SDM predictions. Our pilot study shows that incorporating shifts in land cover improves habitat suitability predictions and leads to contrasting outcomes of future mountain plant distribution. Alpine plants in particular may lose less suitable habitat than standard SDMs predict due to 21st century glacier retreat.

A participatory network was set up to study tree phenology in the Western Alps. We used data collected in 2006 and 2007 on birch, ash, hazel, spruce and larch to assess how local air temperature, altitude and other topographic variables influenced dates of budburst and leaf unfolding. Altitude was, as expected, a main predictor variable of budburst and leafing dates with delays ranging from 2.4 to 3.4 days per 100 m. Ash was the only species with strong evidence of a year difference in the altitudinal gradient with the warm year (2007) characterized by a weaker altitudinal gradient. We found a latitudinal gradient in the appearance of budburst for one coniferous species (larch) and curvature affected leafing in ash. Thermal sum (sum of Degree-Days above 0 °C) was increasing with altitude for budburst (birch, ash and larch) and leafing (birch and ash). Understanding of altitude and topography effects in addition to temperature in phenological models should improve projections of future changes in mountain regions.

The Alpine Chough Pyrrhocorax graculus is a social corvid which now uses food provided by tourist activities in mountain regions (e.g. at ski stations, refuse dumps, picnic areas). Foraging flock size, flock distribution and flock structure of Alpine Choughs were studied in the northern French Alps between 1988 and 1992. Flock size varied during the year, being larger in winter than in summer. Alpine Choughs were not evenly distributed in space, and their numbers depended principally on site-specific factors, such as seasonal human presence. A significant positive correlation existed between Alpine Chough foraging flock size and the local human population. Immature birds gathered in winter in the largest flocks and principally frequented sites with the greatest food availability (e.g. refuse dump). In summer, immatures dispersed, joined small breeding groups and were more homogeneously distributed.

In accordance with their mission and as part of their long-term observation work, Ecrins National Park (NP) is making important contributions to the study and moni-toring of phenomena related to climate change. Its work takes information collected at different meteorological stations and supplements it with analyses of vegetation changes through aerial and satellite images, measuring and monitoring of glaciers, and interdisciplinary programmes focused on high-altitude lakes, mountain pastures and indicator species. Through its mission and long-term observations, Ecrins NP (http://www.ecrins-parcnational.fr/) contributes to the environmental surveillance of many ecosystems. Working within many different networks and in partnership with various research teams, the park participates in the development of a better understanding of the important changes taking place.

Telomeres are specialized non-coding DNA sequences that cap the end of chromosomes and protect genome integrity. Because telomeres shorten during development and their length at maturity is often associated with survival, one hypothesis is that telomere erosion during early growth is closely associated with life history trajectories of individuals and species. Elevation gradients lead to systematic changes in environmental factors, and thus they provide unique opportunities to explore how life history trajectories and telomere dynamics can covary under various environmental conditions. Here, we address this question in chicks of two tit species distributed foremost at low elevation (the great tit Parus major) or at high elevation (the coal tit Periparus ater). With increasing elevation, great tits showed delayed breeding, and their chicks a slower development, higher telomere erosion and shorter telomere length at day 16. Although coal tit parents delayed also their breeding with increasing elevation, their chicks had a faster development, higher telomere erosion but no reduced telomere length at day 16. This last result is explained by coal tit chicks having longer telomeres at day 7 at high than low elevation, thus mitigating effects of fast telomere erosion before fledging. Our findings on life histories support the idea that great tits and coal tits are best adapted to low and high elevation, respectively. Our data on telomere provide however no support for a direct link between early growth rate and telomere dynamics, but underline complex interplays between telomere dynamics and environmental conditions experienced early in life, thereby urging for studies identifying how early life conditions actually determine fledgling’s telomere length

The degree of sexual size dimorphism in a number of different morphological characters was examined in a social corvid, the Alpine Chough, using measurements taken on 178 males and 144 females. A small amount of size dimorphism appeared in all morphological characters, and weight was the most dimorphic character. To identify if Alpine Choughs mate assortatively, measurements of mates were compared in 76 pairs. A positive assortative mating was found on tarsus length, and a small positive trend is suggested between body condition of partners, but that needs to be confirmed with a larger sample size.

I conducted feeding experiments to determine the effect of variations in food availability on individual flocking behaviour and foraging efficiency in a social corvid, the alpine chough Pyrrhocorax graculus, which lives in large flocks all year round. In 37 trials I varied both food quantity and the number of food patches. A decrease in the amount of available food reduced the mean flock size, the proportion of birds that had access to food, and their mean pecking rate. A decrease in the number of patches, on the other hand, reduced only the proportion of birds that had access to food. The number of choughs foraging was not influenced by food competition but depended only on the number visiting the site. Females competed less well than males: when food was made scarce, they frequented the site in the same proportion as did males, but had less access to food. I suggest that in this social corvid, long-term advantages to flocking related to social bonds, such as the maintenance of pair bonds, may compensate for short-term costs such as a reduction in foraging efficiency. Copyright 1999 The Association for the Study of Animal Behaviour.

International audience; The short favorable period of time available for the growth in seasonal environments could constrain the resources allocation between growth and other life-history traits, and the short-term fitness benefits of increased growth rate may prevail over other functions. Accelerated growth rates have been associated with long-term deleterious consequences (e.g., decreased lifespan), and recently oxidative stress (the imbalance between pro-oxidants generation and antioxidant defenses) has been suggested as a mediator of these effects. Here, we examined the impact of elevation on growth rate and self-maintenance parameters (resting metabolism, oxidative damage, and antioxidant defenses) of coal tit chicks (Periparus ater). We predicted that the shorter favorable season at the higher-elevation site could lead to a reallocation of resources towards growth at the expense of self-maintenance processes. We found that chicks at high elevation grew significantly faster in terms of body mass and body size. Chicks from the high-elevation site presented higher resting metabolism, higher oxidative damage level, but similar antioxidant defenses, compared to low-elevation chicks. Interestingly, the chicks exhibiting the better antioxidant defenses at 7 days were also those with the highest resting metabolic rate, and the chicks that grew at the faster rate within the high-elevation site were those with the highest levels of oxidative damage on DNA. Our study supports the idea that increasing elevation leads to a higher growth rate in coal tit chicks, possibly in response to a shorter favorable season. In accordance with life-history theory, a bigger investment in growth was done at the expense of body maintenance, at least in terms of oxidative stress.

Alpine ecosystems will be greatly impacted by climatic change, but other factors, such as land use and invasive species, are likely to play an important role too. Climate can influence ecosystems at several levels. We describe some of them, stressing methodological approaches and available data. Climate can modify species phenology, such as flowering date of plants and hatching date in insects. It can also change directly population demography (survival, reproduction, dispersal), and therefore species distribution. Finally it can effect interactions among species – snow cover for example can affect the success of some predators. One characteristic of alpine ecosystems is the presence of snow cover, but surprisingly the role played by snow is relatively poorly known, mainly for logistical reasons. Even if we have made important progress regarding the development of predictive models, particularly so for distribution of alpine plants, we still need to set up observational and experimental networks which properly take into account the variability of alpine ecosystems and of their interactions with climate.Les écosystèmes alpins vont être grandement influencés par les changements climatiques à venir, mais d’autres facteurs, tels que l’utilisation des terres ou les espèces invasives, pourront aussi jouer un rôle important. Le climat peut influencer les écosystèmes à différents niveaux, et nous en décrivons certains, en mettant l’accent sur les méthodes utilisées et les données disponibles. Le climat peut d’abord modifier la phénologie des espèces, comme la date de floraison des plantes ou la date d’éclosion des insectes. Il peut ensuite affecter directement la démographie des espèces (survie, reproduction, dispersion) et donc à terme leur répartition. Il peut enfin agir sur les interactions entre espèces – le couvert neigeux par exemple modifie le succès de certains prédateurs. Une caractéristique des écosystèmes alpins est la présence d’un manteau neigeux important et pourtant l’influence de la neige reste relativement mal connue, en particulier pour des raisons logistiques. Même si nous avons fait des progrès importants dans le développement de modèles prédictifs, surtout pour ce qui est de la répartition des plantes alpines, il reste à mettre en place des réseaux d’observations et d’expériences permettant de mieux tenir compte de la variabilité des écosystèmes alpins et des interactions avec le climat.

Les écosystèmes alpins vont être grandement influencés par les changements climatiques à venir, mais d’autres facteurs, tels que l’utilisation des terres ou les espèces invasives, pourront aussi jouer un rôle important. Le climat peut influencer les écosystèmes à différents niveaux, et nous en décrivons certains, en mettant l’accent sur les méthodes utilisées et les données disponibles. Le climat peut d’abord modifier la phénologie des espèces, comme la date de floraison des plantes ou la date d’éclosion des insectes. Il peut ensuite affecter directement la démographie des espèces (survie, reproduction, dispersion) et donc à terme leur répartition. Il peut enfin agir sur les interactions entre espèces – le couvert neigeux par exemple modifie le succès de certains prédateurs. Une caractéristique des écosystèmes alpins est la présence d’un manteau neigeux important et pourtant l’influence de la neige reste relativement mal connue, en particulier pour des raisons logistiques. Même si nous avons fait des progrès importants dans le développement de modèles prédictifs, surtout pour ce qui est de la répartition des plantes alpines, il reste à mettre en place des réseaux d’observations et d’expériences permettant de mieux tenir compte de la variabilité des écosystèmes alpins et des interactions avec le climat.Alpine ecosystems will be greatly impacted by climatic change, but other factors, such as land use and invasive species, are likely to play an important role too. Climate can influence ecosystems at several levels. We describe some of them, stressing methodological approaches and available data. Climate can modify species phenology, such as flowering date of plants and hatching date in insects. It can also change directly population demography (survival, reproduction, dispersal), and therefore species distribution. Finally it can effect interactions among species –snow cover for example can affect the success of some predators. One characteristic of alpine ecosystems is the presence of snow cover, but surprisingly the role played by snow is relatively poorly known, mainly for logistical reasons. Even if we have made important progress regarding the development of predictive models, particularly so for distribution of alpine plants, we still need to set up observational and experimental networks which properly take into account the variability of alpine ecosystems and of their interactions with climate.

We analysed the call repertoires of the Red-billed Chough (Pyrrhocorax pyrrhocorax) and the Alpine Chough (Pyrrhocorax graculus) across three continents (Europe, Asia, and Africa) for intraspecific and interspecific differences in call-repertoire size and discuss the factors that could have promoted its evolution. The overall call reper - toire of the Red-billed Chough was twice as large as that of the Alpine Chough, but the number of calls recorded in each population did not differ significantly between the two species. The greater fragmentation of the range of the Red- billed Chough possibly induced its remarkable call-repertoire diversification. Some populations (i.e., those from Ethio - pia, Central Asia, Canaries) had a peculiar call repertoire that overlapped very little with those from other regions; con - sequently, the overall numbers of call types within the species were heavily influenced by these unusual populations and were very large. The call-repertoire size and call-repertoire similarity of populations of both species were affected and constrained by geographic distance. More closely situated or continental populations tended to have a more similar pool of calls (this is probably due to mingling among close populations). Resume : Nous avons analyse le repertoire des cris chez le Crave a bec rouge (Pyrrhocorax pyrrhocorax )e t le Cho- card a bec jaune (Pyrrhocorax graculus) sur trois continents (Europe, Asie et Afrique) par estimation des differences intraspecifiques et interspecifiques dans l'importance du repertoire des cris et par examen des facteurs qui peuvent avoir favorise son evolution. Dans l'ensemble, le repertoire des cris du Crave a bec rouge est deux fois plus important que celui du Chocard a bec jaune, mais le nombre de cris enregistres chez chacune des populations ne differe pas significa- tivement chez les deux especes. La fragmentation plus importante de l'aire de repartition du Crave a bec rouge est sans doute responsable de la diversification remarquable de son repertoire. Certaines populations (i.e., celles de l'Ethiopie, de l'Asie centrale et des iles Canaries) ont des repertoires bizarres avec tres peu de chevauchement avec des oiseaux d'autres regions; en consequence, le nombre global de types de cris au sein de l'espece est fortement influence par ces populations particulieres et est donc tres eleve. L'importance du repertoire et la similarite du repertoire chez les popula- tions des deux especes sont affectees et restreintes par la distance geographique. Les populations proches les unes des autres ou les populations continentales ont tendance a avoir un repertoire plus semblable (probablement a cause des melanges entre populations rapprochees). (Traduit par la Redaction) 1576

The fréquentation of a clumped food resource by a foraging flock of a social corvid species, the Alpine Chough Pyrrhocorax graculus was studied between November 1990 and May 1991 at a refuse tip according to sex and season. Site fréquentation, interactions and success rates were shown to vary with sex and season. Females were less aggressive than males, their success rate was lower, and they principally used low bird density areas where interaction rates were low. Female attendance increased in spring in parallel to their interaction success rate. Among females, those whose weight exceeded the median value were most frequently seen, especially in the area where highest interaction rates were observed. This suggests that alpine choughs use different foraging strategies in order to exploit clumped resources according to their social status (i.e. sex, physical caracteristics) and season., Delestrade Anne. Stratégies d'exploitation des ressources en fonction du sexe et de la saison chez une espèce grégaire, le chocard à bec jaune (Pyrrhocorax graculus). In: Revue d'Écologie (La Terre et La Vie), tome 48, n°2, 1993. pp. 199-206.