Facteurs environnementaux et sociaux influençant la gestion des réserves énergétiques chez le plectrophane des neiges (Plectrophenax nivalis) en hiver

RÉSUMÉ: Une des stratégies d'acclimatation hivernale adoptée par plusieurs passereaux résidents des régions nordiques est l'augmentation journalière et saisonnière des réserves lipidiques. En puisant dans les réserves accumulées pendant la journée, les oiseaux obtiennent l'énergie nécessaire pour survivre les nuits longues et froides et peuvent aussi subsister quand des tempêtes imprévisibles restreignent l'accès à la nourriture. La taille des réserves accumulées en hiver peut varier au sein d’une même espèce en fonction de plusieurs facteurs, principalement 1) les conditions météorologiques (court-terme), 2) les conditions climatiques (long-terme) et 3) le rang social des individus. Cependant, les connaissances sur comment ces trois facteurs peuvent interagir pour influencer la gestion des réserves énergétiques restent limitées. Nous avons utilisé un jeu de données à long-terme reécoltées dans plusieurs sites d'hivernage de l'est du Canada afin d'examiner la gestion des réserves énergétiques en fonction de l'interaction potentielle de facteurs environnementaux et sociaux chez le plectrophane des neiges. Nos résultats ont montré que les oiseaux font des ajustements précis de leurs réserves en fonction des conditions locales à court-terme, en s'engraissant d'avantage les journées où la météo est plus sévère. De plus, nos résultats montrent que les individus occupant les régions de leur aire d'hivernage présentant un climat (tendances historiques) plus froid et neigeux sont plus gras que ceux hivernant dans des régions plus clémentes. Deux mécanismes, mutuellement non-exclusifs, pourraient expliquer ces observations : (1) la présence chez l'espèce de flexibilité phénotypique à court-terme dans l'ajustement des réserves ainsi que (2) la sélection naturelle ayant favorisé l'engraissement chez les populations qui font face à un climat hivernal plus exigeant sur le plan énergétique. Finalement, notre étude a aussi montré que l'environnement social semble avoir un effet régulateur sur les stratégies de gestion des réserves chez l'espèce. Pour un site donneé, les femelles (sexe subordonné) avaient plus de réserves en moyenne que les mâles (sexe dominant) relativement à leur taille structurelle. Notre étude renseigne sur les mécanismes sous-jacents à l'engraissement des passereaux et offre des pistes de réflexion quant aux stratégies d'adaptation qui pourraient permettre au plectrophane des neiges de se maintenir face aux changements climatiques annoncés. -- Mot(s) clé(s) en français : écologie hivernale, écophysiologie des oiseaux, réserves énergétiques, acclimatation hivernale, engraissement hivernal, plectrophane des neiges. -- ABSTRACT: Many small songbirds increase lipid reserves during the wintering period. These reserves are accumulated during the day, acting as the principal source of energy to survive enforced fasting through the night, while also offering a safety margin against starvation in case finding food becomes difficult during the subsequent day(s). Within species, energy reserves are prone to vary with a range of factors, mainly 1) short-term (daily) changes in weather, 2) long-term (historic) climate conditions and 3) social rank of individuals. However, little is known regarding how these factors might interact to influence energy reserve management in passerine birds. Using a long-term (7 year) winter banding dataset from 7 locations across eastern Canada, we examined the relative role of environmental and social factors in influencing winter energy reserve management in the snow bunting (Plectrophenax nivalis). Our results indicate that birds respond to short-term changes in weather by making fine-tuned adjustments of the size of their energy reserves, in that they accumulate more fat on days where the weather is more severe (i.e. heavy snowfall, low temperature). Furthermore, mean energy reserves also increased as long-term trends in climate harshness at a given location increased. Together these results suggest that both short-term phenotypic flexibility in the management of energy reserves as well as selection for phenotypes with differential capacities for fattening across wintering sites are two non- mutually exclusive mechanisms that enable wintering buntings to respond to variation in climatic conditions. We also found that for a given location, females (subordinate sex) consistently exhibited higher fat reserves than males (dominant sex) relative to their body size, potentially suggesting that social dominance may play an additional role in explaining variation in energy reserves in this species. Our findings are also an important first step in determining the adjustments that may allow this species to adapt to future climatic stressors, considering projected climate change in its wintering habitat. Globally, our study expands our knowledge on the winter ecology of the snow bunting and also provides information on the underlying mechanisms regulating fattening in small passerines. -- Mot(s) clé(s) en anglais : winter ecology, avian energetics, energy reserves, winter acclimatization, snow bunting, winter fattening

Caractérisation de modèles murins de la maladie de Parkinson (MPTP, PITX3) et modification des cellules souches hématopoïétiques pour stimuler la production du " Brain-derived neurotrophic factor " (BDNF)

La maladie de Parkinson est une maladie neurodégénérative caractérisée par des dysfonctions locomotrices causées, en grande partie, par la perte de neurones dopaminergiques de la substance noire. Les patients atteints de la maladie de Parkinson présentent un déficit en « brain-derived neurotrophic factors » (BDNF). Cette neurotrophine est nécessaire pour le développement, le maintien et la survie des neurones dopaminergiques. Nous avons utilisé la capacité naturelle des cellules souches hématopoïétiques à infiltrer les régions lésées du cerveau pour libérer ce facteur neurotrophique. Nous avons démontré que la modification des cellules de la moelle osseuse pour favoriser la production du BDNF permet d’améliorer les déficits locomoteurs des souris parkinsoniennes. De plus, la modification des cellules hématopoïétiques permet d’augmenter les niveaux de BDNF dans la substance noire, le cortex et le thalamus. La surproduction de BDNF permet également de stimuler la production de la dopamine au niveau de la substance noire.Parkinson’s disease is a common neurodegenerative disorder characterized by locomotor dysfunctions. These motor symptoms are due to a severe loss of dopaminergic neurons in the substantia nigra pars compacta. Parkinson’s patients also have a deficit in the expression of the brain-derived neurotrophic factor (BDNF). This neurotrophin plays an important role in the development, survival and neurotransmission of dopaminergic neurons. Considering that hematopoietic stem cells can infiltrate damaged brain regions, we have modified these cells to deliver the neurotrophic factor in Parkinson’s disease mouse models. We have demonstrated that modification of bone marrow cells attenuates the locomotor dysfonctions in Parkinson’s mice. In addition, overproduction of BDNF by hematopoietic cells increases BDNF levels in the substantia nigra, cortex and thalamus. Overproduction of BDNF also stimulates biosynthesis of dopamine in the substantia nigra

Tracking Landscape-Scale Movements of Snow Buntings and Weather-Driven Changes in Flock Composition During the Temperate Winter

Nomadic movements of migratory birds are difficult to study, as the scale is beyond the capabilities of hand-held telemetry (10 s of kms) but too fine-scale for long-range tracking devices like geolocators (50–100 km accuracy). Recent widespread installation of automated telemetry receiving stations allowed us, for the first time, to quantify and test predictions about within-winter movements of a presumed nomadic species, the Snow Bunting (Pletrophenax nivalis). We deployed coded radio-transmitters on 40 individual Snow Buntings during two winters (2015-16 and 2016-17) in southern Ontario, Canada, and tracked movements over a 300 by 300 km area with 69–77 active radio-receiving stations (Motus Wildlife Tracking Network). To complement our tracking data, we also examined the influence of weather on the demographics of winter flocks at a single wintering site over 6 consecutive years (n = 9312 tagged birds). We recorded movements of 25 Snow Buntings from the deployment sites to 1–6 different radio recievers (mean 2.68 locations/bird). Birds traveled a minimum average distance of 49 km between detections (range: 3 to 490 km) in the core wintering period of Dec-Feb, and cumulative total movements ranged from 3 to 740 km (average 121 ± 46 km). In March distances between detections increased to an average of 110 km, suggesting an extended early-migration period. Overall, older birds (after-second year or older) tended to move more (higher cumulative distances traveled) than younger (first winter) birds, even during the Dec-Feb period. The long-term banding data revealed that larger, male birds were more likely to be captured in colder and snowier weather, relative to female and smaller birds, suggesting that they can withstand these conditions more easily owing to their body size. We have provided the first direct-tracking data on nomadic winter movements of Snow Buntings, and tested the hypothesis that winter weather drives flock composition at a single site. Site-specific banding data suggest that weather-related changes in flock composition could explain the nomadic, landscape-scale movements of Snow Buntings we observed by using automated telemetry. Future work should explore the importance of resource availability, competition, and predation risk as drivers of winter movements in Snow Buntings

Snow Buntings Maintain Winter-Level Cold Endurance While Migrating to the High Arctic

Arctic breeding songbirds migrate early in the spring and can face winter environments requiring cold endurance throughout their journey. One such species, the snow bunting (Plectrophenax nivalis), is known for its significant thermogenic capacity. Empirical studies suggest that buntings can indeed maintain winter cold acclimatization into the migratory and breeding phenotypes when kept captive on their wintering grounds. This capacity could be advantageous not only for migrating in a cold environment, but also for facing unpredictable Arctic weather on arrival and during preparation for breeding. However, migration also typically leads to declines in the sizes of several body components linked to metabolic performance. As such, buntings could also experience some loss of cold endurance as they migrate. Here, we aimed to determine whether free-living snow buntings maintain a cold acclimatized phenotype during spring migration. Using a multi-year dataset, we compared body composition (body mass, fat stores, and pectoralis muscle thickness), oxygen carrying capacity (hematocrit) and metabolic performance (thermogenic capacity – Msum and maintenance energy expenditure – BMR) of birds captured on their wintering grounds (January–February, Rimouski, QC, 48°N) and during pre-breeding (April–May) in the Arctic (Alert, NU, 82°). Our results show that body mass, fat stores and Msum were similar between the two stages, while hematocrit and pectoralis muscle thickness were lower in pre-breeding birds than in wintering individuals. These results suggest that although tissue degradation during migration may affect flight muscle size, buntings are able to maintain cold endurance (i.e., Msum) up to their Arctic breeding grounds. However, BMR was higher during pre-breeding than during winter, suggesting higher maintenance costs in the Arctic

Facteurs environnementaux et sociaux influençant la gestion des réserves énergétiques chez le plectrophane des neiges (Plectrophenax nivalis) en hiver

RÉSUMÉ: Une des stratégies d'acclimatation hivernale adoptée par plusieurs passereaux résidents des régions nordiques est l'augmentation journalière et saisonnière des réserves lipidiques. En puisant dans les réserves accumulées pendant la journée, les oiseaux obtiennent l'énergie nécessaire pour survivre les nuits longues et froides et peuvent aussi subsister quand des tempêtes imprévisibles restreignent l'accès à la nourriture. La taille des réserves accumulées en hiver peut varier au sein d’une même espèce en fonction de plusieurs facteurs, principalement 1) les conditions météorologiques (court-terme), 2) les conditions climatiques (long-terme) et 3) le rang social des individus. Cependant, les connaissances sur comment ces trois facteurs peuvent interagir pour influencer la gestion des réserves énergétiques restent limitées. Nous avons utilisé un jeu de données à long-terme reécoltées dans plusieurs sites d'hivernage de l'est du Canada afin d'examiner la gestion des réserves énergétiques en fonction de l'interaction potentielle de facteurs environnementaux et sociaux chez le plectrophane des neiges. Nos résultats ont montré que les oiseaux font des ajustements précis de leurs réserves en fonction des conditions locales à court-terme, en s'engraissant d'avantage les journées où la météo est plus sévère. De plus, nos résultats montrent que les individus occupant les régions de leur aire d'hivernage présentant un climat (tendances historiques) plus froid et neigeux sont plus gras que ceux hivernant dans des régions plus clémentes. Deux mécanismes, mutuellement non-exclusifs, pourraient expliquer ces observations : (1) la présence chez l'espèce de flexibilité phénotypique à court-terme dans l'ajustement des réserves ainsi que (2) la sélection naturelle ayant favorisé l'engraissement chez les populations qui font face à un climat hivernal plus exigeant sur le plan énergétique. Finalement, notre étude a aussi montré que l'environnement social semble avoir un effet régulateur sur les stratégies de gestion des réserves chez l'espèce. Pour un site donneé, les femelles (sexe subordonné) avaient plus de réserves en moyenne que les mâles (sexe dominant) relativement à leur taille structurelle. Notre étude renseigne sur les mécanismes sous-jacents à l'engraissement des passereaux et offre des pistes de réflexion quant aux stratégies d'adaptation qui pourraient permettre au plectrophane des neiges de se maintenir face aux changements climatiques annoncés. -- Mot(s) clé(s) en français : écologie hivernale, écophysiologie des oiseaux, réserves énergétiques, acclimatation hivernale, engraissement hivernal, plectrophane des neiges. -- ABSTRACT: Many small songbirds increase lipid reserves during the wintering period. These reserves are accumulated during the day, acting as the principal source of energy to survive enforced fasting through the night, while also offering a safety margin against starvation in case finding food becomes difficult during the subsequent day(s). Within species, energy reserves are prone to vary with a range of factors, mainly 1) short-term (daily) changes in weather, 2) long-term (historic) climate conditions and 3) social rank of individuals. However, little is known regarding how these factors might interact to influence energy reserve management in passerine birds. Using a long-term (7 year) winter banding dataset from 7 locations across eastern Canada, we examined the relative role of environmental and social factors in influencing winter energy reserve management in the snow bunting (Plectrophenax nivalis). Our results indicate that birds respond to short-term changes in weather by making fine-tuned adjustments of the size of their energy reserves, in that they accumulate more fat on days where the weather is more severe (i.e. heavy snowfall, low temperature). Furthermore, mean energy reserves also increased as long-term trends in climate harshness at a given location increased. Together these results suggest that both short-term phenotypic flexibility in the management of energy reserves as well as selection for phenotypes with differential capacities for fattening across wintering sites are two non- mutually exclusive mechanisms that enable wintering buntings to respond to variation in climatic conditions. We also found that for a given location, females (subordinate sex) consistently exhibited higher fat reserves than males (dominant sex) relative to their body size, potentially suggesting that social dominance may play an additional role in explaining variation in energy reserves in this species. Our findings are also an important first step in determining the adjustments that may allow this species to adapt to future climatic stressors, considering projected climate change in its wintering habitat. Globally, our study expands our knowledge on the winter ecology of the snow bunting and also provides information on the underlying mechanisms regulating fattening in small passerines. -- Mot(s) clé(s) en anglais : winter ecology, avian energetics, energy reserves, winter acclimatization, snow bunting, winter fattening

Snow bunting winter banding data and associated daily weather variables for each individual capture

Snow bunting winter (Nov 1 to Mar 20) banding data (including age, sex, banding location, body mass, wing chord, fat score and time of capture) merged to associated daily weather data (including mean temperature, minimal temperature, maximal temperature, snow depth, total snowfall, absolute humidity, maximal wing gust and cloud cover (for the period 2009-2015 for 8 locations in eastern Canada. Banding data were obtained from both the Canadian bird banding office and the citizen science project Canadian Snow Bunting Network. Daily weather variables were merged to banding data and were extracted from the following three sources : 1) environment and climate change weather office online, 2) ministère du développement durable de l'environnement et de la lutte contre les changements climatiques et 3) National snow and ice data center. Only individual record for which a complete set of information was available for every individual (i.e. sex, age, wing chord, fat score, body mass, time of capture) and only banding entries with an associated complete set of weather variables were kept in the dataset. Excel was used to calculate weather averaged over the three days preceding capture. R Software (3.2.1) was used to create the datafile and do all other manipulations

Data from: Flexible response to short-term weather in a cold-adapted songbird

To improve survival during winter, temperate species use a variety of behavioural and physiological adaptations. Among songbirds, the maintenance of lipid reserves is a widely-used strategy to cope with the severity of winter; however, little is known regarding how multiple synchronously acting environmental mechanisms work together to drive these effects. In a context where temperate winter conditions are becoming more variable, it is important to widen our understanding regarding the flexible adaptations that may allow wintering species to adjust to projected climate change. Using a long-term dataset collected across multiple wintering populations (7 years; 8 locations), we analyzed the effects of daily variation in weather (e.g., temperature, snowfall) on the variation in energy reserves (i.e., fat stores) of wintering snow buntings (Plectrophenax nivalis). Our results support the prediction that birds carry more reserves to increase the safety margin against starvation when conditions are energy-demanding and access to food is unpredictable (i.e., colder, snowier conditions). Birds responded to daily changes in weather by increasing their reserves as conditions deteriorated, with maximal temperatures and snow depth being the most important predictors of fattening decisions. We also found that females consistently exhibited higher fat reserves than males relative to their body size, suggesting that differential physiological adaptations among sexes or social dominance may play an additional role in explaining variation in energy reserves across individuals in this species. Overall, our findings increase knowledge on phenotypic adjustments used by species wintering in temperate zones to match variation in their environment

Flexible response to short-term weather in a cold-adapted songbird

To improve survival during winter, temperate species use a variety of behavioural and physiological adaptations. Among songbirds, the maintenance of lipid reserves is a widely-used strategy to cope with the severity of winter; however, little is known regarding how multiple synchronously acting environmental mechanisms work together to drive these effects. In a context where temperate winter conditions are becoming more variable, it is important to widen our understanding regarding the flexible adaptations that may allow wintering species to adjust to projected climate change. Using a long-term dataset collected across multiple wintering populations (7 years; 8 locations), we analyzed the effects of daily variation in weather (e.g. temperature, snowfall) on the variation in energy reserves (i.e. fat stores) of wintering snow buntings Plectrophenax nivalis. Our results support the prediction that birds carry more reserves to increase the safety margin against starvation when conditions are energy-demanding and access to food is unpredictable (i.e. colder, snowier conditions). Birds responded to daily changes in weather by increasing their reserves as conditions deteriorated, with maximal temperatures and snow depth being the most important predictors of fattening decisions. We also found that females consistently exhibited higher fat reserves than males relative to their body size, suggesting that differential physiological adaptations among sexes or social dominance may play an additional role in explaining variation in energy reserves across individuals in this species. Overall, our findings increase knowledge on phenotypic adjustments used by species wintering in temperate zones to match variation in their environment

Tracking Landscape-Scale Movements of Snow Buntings and Weather-Driven Changes in Flock Composition During the Temperate Winter

Nomadic movements of migratory birds are difficult to study, as the scale is beyond the capabilities of hand-held telemetry (10 s of kms) but too fine-scale for long-range tracking devices like geolocators (50–100 km accuracy). Recent widespread installation of automated telemetry receiving stations allowed us, for the first time, to quantify and test predictions about within-winter movements of a presumed nomadic species, the Snow Bunting (Pletrophenax nivalis). We deployed coded radio-transmitters on 40 individual Snow Buntings during two winters (2015-16 and 2016-17) in southern Ontario, Canada, and tracked movements over a 300 by 300 km area with 69–77 active radio-receiving stations (Motus Wildlife Tracking Network). To complement our tracking data, we also examined the influence of weather on the demographics of winter flocks at a single wintering site over 6 consecutive years (n = 9312 tagged birds). We recorded movements of 25 Snow Buntings from the deployment sites to 1–6 different radio recievers (mean 2.68 locations/bird). Birds traveled a minimum average distance of 49 km between detections (range: 3 to 490 km) in the core wintering period of Dec-Feb, and cumulative total movements ranged from 3 to 740 km (average 121 ± 46 km). In March distances between detections increased to an average of 110 km, suggesting an extended early-migration period. Overall, older birds (after-second year or older) tended to move more (higher cumulative distances traveled) than younger (first winter) birds, even during the Dec-Feb period. The long-term banding data revealed that larger, male birds were more likely to be captured in colder and snowier weather, relative to female and smaller birds, suggesting that they can withstand these conditions more easily owing to their body size. We have provided the first direct-tracking data on nomadic winter movements of Snow Buntings, and tested the hypothesis that winter weather drives flock composition at a single site. Site-specific banding data suggest that weather-related changes in flock composition could explain the nomadic, landscape-scale movements of Snow Buntings we observed by using automated telemetry. Future work should explore the importance of resource availability, competition, and predation risk as drivers of winter movements in Snow Buntings

Snow Buntings Maintain Winter-Level Cold Endurance While Migrating to the High Arctic

Arctic breeding songbirds migrate early in the spring and can face winter environments requiring cold endurance throughout their journey. One such species, the snow bunting (Plectrophenax nivalis), is known for its significant thermogenic capacity. Empirical studies suggest that buntings can indeed maintain winter cold acclimatization into the migratory and breeding phenotypes when kept captive on their wintering grounds. This capacity could be advantageous not only for migrating in a cold environment, but also for facing unpredictable Arctic weather on arrival and during preparation for breeding. However, migration also typically leads to declines in the sizes of several body components linked to metabolic performance. As such, buntings could also experience some loss of cold endurance as they migrate. Here, we aimed to determine whether free-living snow buntings maintain a cold acclimatized phenotype during spring migration. Using a multi-year dataset, we compared body composition (body mass, fat stores, and pectoralis muscle thickness), oxygen carrying capacity (hematocrit) and metabolic performance (thermogenic capacity – Msum and maintenance energy expenditure – BMR) of birds captured on their wintering grounds (January–February, Rimouski, QC, 48°N) and during pre-breeding (April–May) in the Arctic (Alert, NU, 82°). Our results show that body mass, fat stores and Msum were similar between the two stages, while hematocrit and pectoralis muscle thickness were lower in pre-breeding birds than in wintering individuals. These results suggest that although tissue degradation during migration may affect flight muscle size, buntings are able to maintain cold endurance (i.e., Msum) up to their Arctic breeding grounds. However, BMR was higher during pre-breeding than during winter, suggesting higher maintenance costs in the Arctic