Effet du rang social sur les stratégies hivernales de gestion de l'energie chez le junco ardoise (Junco hyemalis)

L'objectif de la présente étude était d'explorer les stratégies hivernales de gestion de l'énergie chez les passereaux dans un contexte social. Les prédictions émises étaient que dans un groupe social soumis à des conditions hivernales, le rang hiérarchique devrait affecter 1) le taux métabolique des individus, 2) l'accès à la ressource alimentaire et donc le niveau d'engraissement journalier et 3) le déficit énergétique en conditions difficiles impliquant une utilisation de l'hypothermie facultative variable en fonction des rangs. Durant les hivers 1996 et 1997, des groupes de juncos ardoisés, Junco hyemalis, ont été suivis en conditions expérimentales. La première année, la totalité des expériences se sont déroulées en volière sur le campus de l'Université de Sherbrooke. L'année suivante, une section respirométrie en laboratoire, pour évaluer l'effet du rang social sur le métabolisme, a été ajoutée. Les groupes formés étaient composés de quatre individus et suivis durant des périodes de cinq jours. Les rangs sociaux étaient déterminés par observations directes. Chaque oiseau portait un émetteur thermosensible permettant d'enregistrer en continu sa température corporelle par télémétrie. Un perchoir installé face à une mangeoire était raccordé à un système d'enregistrement de la masse et d'identification. De cette façon, le nombre de visites à la mangeoire, la durée des visites de même que la masse de chaque individu au moment précis de ces visites ont pu être enregistrés durant chaque expérience.--Résumé abrégé par UMI

Chronique : Nouveau Code civil du Québec

«L'action paulienne, rebaptisée «action en inopposabilité» à l'occasion de la réforme du Code civil, peut s'avérer fort utile au créancier désireux de sauvegarder le patrimoine de son débiteur. Considéré sous un autre angle, ce recours se présente plutôt comme une immixtion grave dans les affaires du débiteur et des tiers qui acceptent de contracter avec lui. L'un des aspects les plus intéressants de l'action en inopposabilité réside donc dans la recherche d'un équilibre entre les intérêts des différentes parties au litige. Or, en matière de contrats à titre onéreux, l'identification de ce point d'équilibre passe traditionnellement par la notion de bonne foi des parties à l'acte attaqué. […]

No common pesticides detected in snow buntings utilizing a farmland landscape in eastern Québec

Many species of migratory birds are declining worldwide, including throughout North America. Some of the most cited causes of decline are linked to climate change, urbanization, and growth in agriculture. Across eastern Canada, a number of insecticides and herbicides are commonly sprayed before and during the grain growing season to control pests and foliage competitors. During wintering and migration, a declining Arctic-breeding songbird, the snow bunting (Plectrophenax nivalis), utilizes open farmlands of southern Canada; therefore, this could be a period when the species is most exposed to these pesticides. We tested snow bunting tissues (blood and liver) for the 4 pesticides most commonly used in grain agriculture in Canada: atrazine, chlothianidin, imidacloprid, and glyphosate, as well as a glyphosate derivative (aminomethylphosphic acid, AMPA). Although this species is thought to forage in grain fields during autumn through spring, we found no detectable traces of any of the five substances. Wintering buntings may either not be exposed to these pesticides during their presence in agriculture fields or, given the rapid turnover of these pesticides in the blood and tissues, be exposed to doses below detection level in samples

One-pot photochemical ring-opening/cleavage approach for the synthesis and decoding of cyclic peptide libraries

A novel dual ring-opening/cleavage strategy to determine the sequence of cyclic peptides from one bead, one compound libraries is described. The approach uses a photolabile residue within the macrocycle and as a linker to allow a simultaneous ring opening and cleavage from the beads upon UV irradiation and provide linearized molecules. Cyclic peptides of five to nine residues were synthesized and the generated linear peptides successfully sequenced by tandem mass spectrometry

Chickadees Faced with Unpredictable Food Increase Fat Reserves but Certain Components of Their Immune Function Decline

In winter, temperate resident birds are often faced with periodic low natural food availability. This reduction or unpredictability in resource availability might then have a negative impact on immune function, given that immune system support is highly resource dependent. We investigated the balance between energetic and immune management in captive black-capped chickadees (Poecile atricapilus) by manipulating the predictability of resources. The control group received food ad lib. every day, while the experimental group received a reduced amount of food on random days and food ad lib. on all other days. We measured two key metrics of energetic management (body and fat mass) as well as a suite of immune system components. Compared with control birds, experimental birds maintained significantly higher total body and fat mass, had lower acute phase protein concentrations, and had decreased body temperature and lost more body mass during the fever response following injection with lipopolysaccharides. Interestingly, birds in both groups had similar levels of complement lysis, delayed-type hypersensitivity response (phytohemagglutinin), and primary antibody production (keyhole limpet hemocyanin). This experiment demonstrates that black-capped chickadees strategically increase their fat mass in response to decreased food availability and that this might allow the birds to maintain most of the immune system unaltered, except some of the most costly immune components

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

Chickadees faced with unpredictable food increase fat reserves but certain components of their immune function decline

In winter, temperate resident birds are often faced with periodic low natural food availability. This reduction or unpredictability in resource availability might then have a negative impact on immune function, given that immune system support is highly resource dependent. We investigated the balance between energetic and immune management in captive black-capped chickadees (Poecile atricapilus) by manipulating the predictability of resources. The control group received food ad lib. every day, while the experimental group received a reduced amount of food on random days and food ad lib. on all other days. We measured two key metrics of energetic management (body and fat mass) as well as a suite of immune system components. Compared with control birds, experimental birds maintained significantly higher total body and fat mass, had lower acute phase protein concentrations, and had decreased body temperature and lost more body mass during the fever response following injection with lipopolysaccharides. Interestingly, birds in both groups had similar levels of complement lysis, delayed-type hypersensitivity response (phytohemagglutinin), and primary antibody production (keyhole limpet hemocyanin). This experiment demonstrates that black-capped chickadees strategically increase their fat mass in response to decreased food availability and that this might allow the birds to maintain most of the immune system unaltered, except some of the most costly immune components

Early life neonicotinoid exposure results in proximal benefits and ultimate carryover effects

Neonicotinoids are insecticides widely used as seed treatments that appear to have multiple negative effects on birds at a diversity of biological scales. Adult birds exposed to a low dose of imidacloprid, one of the most commonly used neonicotinoids, presented reduced fat stores, delayed migration and potentially altered orientation. However, little is known on the effect of imidacloprid on birds growth rate despite studies that have documented disruptive effects of low imidacloprid doses on thyroid gland communication. We performed a 2 × 2 factorial design experiment in Zebra finches, in which nestling birds were exposed to a very low dose (0.205 mg kg body mass - 1) of imidacloprid combined with food restriction during posthatch development. During the early developmental period, imidacloprid exposure resulted in an improvement of body condition index in treated nestlings relative to controls. Imidacloprid also led to compensatory growth in food restricted nestlings. This early life neonicotinoid exposure also carried over to adult age, with exposed birds showing higher lean mass and basal metabolic rate than controls at ages of 90–800 days. This study presents the first evidence that very low-dose neonicotinoid exposure during early life can permanently alter adult phenotype in birds

Consequences of being phenotypically mismatched with the environment: Rapid muscle ultrastructural changes in cold-shocked black-capped chickadees (Poecile atricapillus)

Phenotypic flexibility has received considerable attention in the last decade; however, whereas many studies have reported amplitude of variation in phenotypic traits, much less attention has focused on the rate at which traits can adjust in response to sudden changes in the environment. We investigated whole animal and muscle phenotypic changes occurring in black-capped chickadees (Poecile atricapillus) acclimated to cold (-5°C) and warm (20°C) temperatures in the first 3 h following a 15°C temperature drop (over 3 h). Before the temperature change, cold-acclimated birds were consuming 95% more food, were carrying twice as much body fat, and had 23% larger pectoralis muscle fiber diameters than individuals kept at 20°C. In the 3 h following the temperature drop, these same birds altered their pectoralis muscle ultrastructure by increasing the number of capillaries per fiber area and the number of nuclei per millimeter of fiber by 22%, consequently leading to a 22% decrease in myonuclear domain (amount of cytoplasm serviced per nucleus), whereas no such changes were observed in the warm-acclimated birds. To our knowledge, this is the first demonstration of such a rapid adjustment in muscle fiber ultrastructure in vertebrates. These results support the hypothesis that chickadees maintaining a cold phenotype are better prepared than warm-phenotype individuals to respond to a sudden decline in temperature, such as what may be experienced in their natural wintering environment