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31 results on '"Vezina, Francois"'

12. Avian Behavioral and Physiological Responses to Challenging Thermal Environments and Extreme Weather Events

Author

Swanson, David L., Vezina, Francois, Nord, Andreas, McKechnie, Andrew, Swanson, David L., Vezina, Francois, Nord, Andreas, and McKechnie, Andrew

Abstract

Birds occupy habitats ranging from Antarctic ice shelves and Arctic tundra to low-latitude deserts and lowland rainforests, and so are exposed to the full range of climates present on Earth. Cold, hot, or variable (on a variety of temporal scales) thermal conditions can present significant thermoregulatory challenges to birds, which typically must maintain body temperatures within narrow physiological tolerance limits. Such challenges may occur in all stages of the annual cycle and in all life stages of birds, so the ability to adjust to these conditions is required to maintain stable populations through time. For this Research Topic, we broadly define a challenging thermal environment as one necessitating behavioral or physiological adjustments to maintain body temperatures at levels appropriate for continued physiological function.Avian abilities to respond to extreme cold and heat are defined by thermoregulatory capacities for heat production or dissipation, respectively. Behavioral responses to temperature challenges can reduce the necessity for and magnitude of physiological adjustments, so together, physiological capacities and behavioral responses determine the probability of survival in thermally challenging situations. Moreover, thermal conditions experienced during reproduction can affect parental investment in the nesting effort and, independently, alter the course of nestling development, with potentially long-term consequences. Behavioral responses to these conditions as well as physiological responses at multiple levels of organization, from organisms to molecules, allow birds to tolerate thermal challenges. Our knowledge of the mechanisms by which birds respond, the time course for such responses, and the impacts on fitness, however, remain incompletely understood. Studies examining behavioral and physiological responses of birds to extreme and/or seasonally variable climates have been a research focus for decades, but recent advances in methods of me

Published
2022

25. Thermogenic side effects to migratory predisposition in shorebirds

Author

Vezina, Francois, Jalvingh, Kirsten M., Dekinga, Anne, and Piersma, Theunis

Subjects
Shore birds -- Physiological aspects, Animal heat -- Analysis, Basal metabolism -- Physiological aspects, Biological sciences
Abstract

In the calidrine sandpiper red knot (Calidris canutus), the weeks preceding takeoff for long-distance migration are characterized by a rapid increase in body mass, largely made up of fat but also including a significant proportion of lean tissue. Before takeoff, the pectoral muscles are known to hypertrophy in preparation for endurance flight without any specific training. Because birds facing cold environments counterbalance heat loss through shivering thermogenesis, and since pectoral muscles represent a large proportion of avian body mass, we asked the question whether muscle hypertrophy in preparation for long-distance endurance flight would induce improvements in thermogenic capacity. We acclimated red knots to different controlled thermal environments: 26[degrees]C, 5[degrees]C, and variable conditions tracking outdoor temperatures. We then studied within-individual variations in body mass, pectoral muscle size (measured by ultrasound), and metabolic parameters [basal metabolic rate (BMR) and summit metabolic rate ([M.sub.sum])] throughout a 3-mo period enclosing the migratory gain and loss of mass. The gain in body mass during the fattening period was associated with increases in pectoral muscle thickness and thermogenic capacity independent of thermal acclimation. Regardless of their thermal treatment, birds showing the largest increases in body mass also exhibited the largest increases in [M.sub.sum.]. We conclude that migratory fattening is accompanied by thermoregulatory side effects. The gain of body mass and muscle hypertrophy improve thermogenic capacity independent of thermal acclimation in this species. Whether this represents an ecological advantage depends on the ambient temperature at the time of fattening. muscle mass; summit metabolic rate; basal metabolic rate; thermogenic capacity; phenotypic flexibility

Published
2007

31. Phenotypic compromises in a long-distance migrant during the transition from migration to reproduction in the High Arctic

Author

Vezina, Francois, Williams, Tony D., Piersma, Theunis, Morrison, R. I. Guy, and Piersma group

Subjects
energetics, polar environment, phenotypic flexibility, thermoregulation, BODY-COMPOSITION, arrival biology, EGG-PRODUCTION, SEASONAL-VARIATION, BASAL METABOLIC-RATE, PECTORAL MUSCLE MASS, ENERGY-EXPENDITURE, RED KNOTS, KNOTS CALIDRIS-CANUTUS, reproduction, COST-BENEFIT-ANALYSIS, breeding, basal metabolic rate, life-history stages, AEROBIC PERFORMANCE VARIATION, physiological conflicts
Abstract

1. Seasonal carry-over effects may be important structuring components of avian life-history cycles. However, little is known on physiological transitions between stages and on phenotypic compromises that may be made at such time to improve fitness. 2. We studied postmigratory body remodelling in red knots (Calidris canutus islandica) arriving on the Arctic breeding grounds. Our objectives were to determine the effects of body reconstruction and preparation for breeding on maintenance energy costs and to determine whether weather conditions can force compromises between functions required for postmigration recovery of body composition, thermoregulation and breeding. 3. During two consecutive springs at the northernmost land on Earth (Alert, Ellesmere Island, Canada, 82 degrees 30' N), we monitored changes in knots post- arrival body stores. Using ultrasonography, we also tracked changes in gizzard size, an indicator of gut size, and pectoral muscle thickness, not only an endogenous protein source but also a thermogenic organ. We measured basal metabolic rate (BMR) throughout reconstruction and compared it with BMR of nonbreeding red knots wintering in the Dutch Wadden Sea. 4. Arriving knots faced temperatures up to 13 degrees C lower than during midwinter. Birds arrived with large body stores and pectoral muscles, which declined in size while they grew their gizzard and prepared for breeding. BMR at arrival was indistinguishable from winter BMR and increased linearly throughout reconstruction. BMR increased up to 69% faster in females than males, likely due to the development of their reproductive organs. 5. Birds had lower body stores but larger muscles in the colder year, and muscle loss was correlated with the warming of spring temperatures. Therefore, muscles would not only serve as a nutrient source, but their thermogenic function could also provide the flexibility to cope with high thermostatic costs in the spring. However, retaining muscles for shivering may limit protein recirculation and delay the onset of breeding. 6. Postmigratory recovery therefore involves significant energy costs and arriving birds likely have to make physiological compromises, depending on spring conditions, which may impact on fitness. Although this period is clearly critical in the life cycle of red knots, it is one of the least understood life- history stages in Arctic- breeding shorebirds.

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