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Leonida Fusani - One of the best experts on this subject based on the ideXlab platform.
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energy stores oxidative balance and sleep in migratory garden warblers Sylvia Borin and whitethroats Sylvia communis at a spring stopover site
Integrative organismal biology (Oxford England), 2020Co-Authors: Leonida Fusani, Scott R. Mcwilliams, Massimiliano Cardinale, Ivan Maggini, Andrea Ferretti, Niels Christian RattenborgAbstract:Twice a year, thousands of migratory bird species cover huge distances between their wintering and breeding grounds. Prior to migration, birds become hyperphagic and accumulate large energy reserves (King and Farner 1965; Odum 1960; McWilliams and Karasov 2005). During the crossings of large ecological barriers such as deserts or seas, birds perform multi-hour flights that can lead to depletion of their energy stores and to a generalized physiological stress, forcing them to make stopovers at the first suitable sites found after the barrier to rest and restore energy reserves (Schmaljohann et al. 2007). The physiological condition at arrival, in particular the extent of fat reserves, has a major influence on stopover behavior (Fusani et al. 2009; Goymann et al. 2010) and, time spent at the stopover site depends on the interplay between body condition at arrival (Dierschke and Delingat 2001; Goymann et al. 2010; Cohen et al. 2014; Smith and McWilliams 2014; Dossman et al. 2018) and the speed at which birds can restore their energy reserves (Lindstrom 2003; Gomez et al. 2017). Migration is one of the most intense energy demanding life history stages, during which the highest mortality occurs (Sillett and Holmes 2002; Alerstam et al. 2003). Moreover, it is often associated with drastic physiological and behavioral changes other than the rapid gain and loss of energy stores. Several diurnal species, including a large proportion of passerine birds, become nocturnal migrants (Berthold 1973, 1996; Gwinner 1996). Flying at night and eating to accumulate energy reserves during the day limits the time available to sleep, which may become a constraint during this life history stage. Sleep is essential for all organisms (Shaw et al. 2002) and its deprivation may have dramatic consequences (Karni et al. 1994; Stickgold et al. 2000; Van Dongen et al. 2003), leading in the worst case to death (Rechtschaffen et al. 1983; Rechtschaffen and Bergmann 2002; Shaw et al. 2002). A large part of a bird’s life is spent sleeping (Toates 1980) but the function of this behavior is, in general, poorly understood. Several functions have been hypothesized, such as physiological restoration (Adam 1980; Reimund 1994; Mignot 2008), energy conservation (Berger 1975) and allocation (Schmidt 2014), clearance of metabolic waste products (Xie et al. 2013; Lim et al. 2013; Fultz et al. 2019), or memory consolidation (Maquet 2001; Stickgold et al. 2001). Among these, metabolic clearance has attracted considerable attention (Xie et al. 2013; Zhang et al. 2018). One group of molecules that might require clearance are the so-called reactive oxygen species (ROS) (Reimund 1994), atoms, or molecules with an unpaired electron. Given their chemical nature, these metabolites are highly reactive with biological molecules (i.e., proteins, lipids, and DNA) and can cause serious damage to the organism (Kregel and Zhang 2007; Cooper-Mullin and McWilliams 2016; Skrip and McWilliams 2016). Organisms can build antioxidant capacity (AOX), which can counteract ROS by reducing their reactivity, by upregulating antioxidant enzymes (enzymatic AOX) and by consuming dietary antioxidants (non-enzymatic AOX). According to the “free radical flux theory of sleep,” sleep clears ROS that have accumulated in the brain during wakefulness by reducing neurons’ activity and increasing enzymatic antioxidant mechanisms (Reimund 1994). Some evidence supporting the free radical flux theory has been found in Drosophila, where high ROS concentration in neurons directly triggers sleep (Hill et al. 2020). Moreover, the brain oxidative balance could be influenced by ROS produced in other tissues (e.g., liver, muscles, and red blood cells) and circulating antioxidants transported by the bloodstream. In this perspective, sleep may provide a direct antioxidant benefit to the brain and also play an important role in the maintenance of the oxidative balance in the periphery of the body. If sleep functions as, or allocates energy to, an antioxidant defense for the whole organism, it should be responsive to circulating ROS and thus may influence the oxidative status of the organism. Although endurance migratory flights have been shown to increase ROS production (Costantini et al. 2008; Jenni-Eiermann et al. 2014), whether intense refueling bouts (Lindstrom 2003; Maggini et al. 2015) influence ROS concentration remains debated. Previous studies conducted on mammals showed that a high caloric intake is associated with high oxidative damage (Masoro 2000; Sohal and Weindruch 1996; Weindruch and Sohal 1997). Eikenaar et al. (2016) found that northern wheatears (Oenanthe oenanthe) that were experimentally fasted and refed and thus rapidly refueling did not increase oxidative damage, at least in part because of increased AOX. Skrip et al. (2015) also found that two species of free-living warblers that were fattening in preparation for fall migration increased AOX as they built fat stores; however, oxidative damage was also higher in fatter birds suggesting an inescapable hazard of using primarily fats as fuel. Moreover, sleep restriction experienced during migratory periods (Rattenborg et al. 2004) should reduce ROS clearance and lead to a further increase in circulating ROS levels. According to the hypothesis of an antioxidant function of sleep (Reimund 1994), sleeping during stopovers might help to reduce ROS concentration. A few field observations are in line with this hypothesis. Several European migratory species were reported to show diurnal sleep after crossing ecological barriers such as the Sahara Desert (Jenni-Eiermann et al. 2011) and the Mediterranean (Schwilch et al. 2002). For example, at Saharan stopover sites, migratory birds in good condition sleep during most of the day, despite having sufficient energy reserves to continue migration (Bairlein 1985; Biebach et al. 1986). The proportion of time spent sleeping/active, during both day and night, is strongly dependent on the physiological condition at arrival (Fusani et al. 2009; Ferretti et al. 2019b). Altogether, these studies suggest that migratory warblers, during both fall (Bairlein 1985; Biebach et al. 1986) and spring (Fusani et al. 2009; Ferretti et al. 2019b) migration, profit from stopover sites after crossing large ecological barriers to recover from sleep loss accumulated during non-stop flights. In addition, recent work from our group has shown that the posture adopted during sleep may influence energy conservation (Ferretti et al. 2019b). Birds can sleep in a tucked posture, in which the head is turned backward and tucked in the scapular feathers, or untucked, with the head pulled toward the body facing forward (Amlaner and Ball 1983). Lean migrating garden warblers (Sylvia Borin) sleep mainly tucked in to reduce heat loss through the head, and this posture reduces conductance and, therefore, metabolic rate. By contrast, birds with large energy reserves expend more energy while sleeping untucked but react more quickly to threats. Thus, sleep posture preference during migration is the result of a trade-off between energy consumption and anti-predator vigilance (Ferretti et al. 2019b). In the present study, we investigated the relationship between oxidative status, energy stores, food intake, and sleep in two migratory songbird species, the garden warbler and the whitethroat (Sylvia communis), at a Mediterranean stopover site during spring migration. Both species are long-distance migrants that cross similar large ecological barriers, and are abundant at our field site. Based on previous studies (Fusani et al. 2009; Goymann et al. 2010; Eikenaar and Schlafke 2013; Lupi et al. 2016), we expected birds with poor energy reserves to invest more time in energy recovery during the day and to sleep during most of the night with the head tucked. Birds with a large amount of energy reserves, on the contrary, should show a mainly untucked diurnal sleep pattern and higher nocturnal restlessness. Within this scenario, we hypothesized that there is a correlation between the oxidative status and the amount and type of sleep. Birds that land at the stopover site after an endurance flight are likely to have high ROS concentration. If sleep facilitates recovery from increased ROS, we predict that birds with higher levels of ROS will sleep longer, unless these birds also have a high antioxidant capacity. Moreover, birds with a high oxidative unbalance where pro-oxidant exceed antioxidants are expected to display a tucked sleep posture more often, which allows for deeper sleep and probably more efficient recovery from oxidative stress.
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Effects of body condition and food intake on stop-over decisions in Garden Warblers and European Robins during spring migration
Journal of Ornithology, 2017Co-Authors: Sara Lupi, Wolfgang Goymann, Massimiliano Cardinale, Alfonso Rojas Mora, Ivan Maggini, Leonida FusaniAbstract:During migration, birds need to optimize their time and/or energy management, especially during stop-overs. Previous studies with caged birds under controlled condition support the notion that departure decisions are condition-dependent, but they did not take into account the availability or the actual intake of food. In the study reported here we investigated whether food intake interacts with condition in influencing migratory disposition in temporarily caged wild migrants. We conducted the study on Garden Warblers (Sylvia Borin) and European Robins (Erithacus rubecula) at a spring stop-over site that is reached after a long non-stop flight over the Mediterranean Sea. The birds were held in cages during the day and the first night following capture, and their locomotor activity, food intake, and body mass change were recorded. In both species, food intake was positively correlated with body mass change. Body condition was positively correlated with migratory restlessness (Zugunruhe) in both species and was also negatively related to diurnal activity in Garden Warblers. Food intake was negatively correlated with diurnal activity in Garden Warblers. When only birds with low fat scores were considered, we found a positive effect of food intake on Zugunruhe in Garden Warblers. In general, European Robins consumed less food than Garden Warblers and no significant effects on Zugunruhe were found. Our results show that food intake interacts with condition in affecting migratory behavior during stop-overs. In particular, food intake may induce Garden Warblers with low fat stores at arrival to leave a stop-over site earlier. The large individual variability in food consumption supports the notion that birds vary in their capacity to refuel soon after arrival at a stop-over site. Overall, our work suggests that the decision to stay at the stop-over site or to resume migration depends on the interaction of condition, refueling capacity and rate, and migratory strategy.
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ghrelin affects stopover decisions and food intake in a long distance migrant
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Wolfgang Goymann, Sara Lupi, Massimiliano Cardinale, Hiroyuki Kaiya, Leonida FusaniAbstract:Abstract Billions of birds migrate long distances to either reach breeding areas or to spend the winter at more benign places. On migration, most passerines frequently stop over to rest and replenish their fuel reserves. To date, we know little regarding how they decide that they are ready to continue their journey. What physiological signals tell a bird’s brain that its fuel reserves are sufficient to resume migration? A network of hormones regulates food intake and body mass in vertebrates, including the recently discovered peptide hormone, ghrelin. Here, we show that ghrelin reflects body condition and influences migratory behavior of wild birds. We measured ghrelin levels of wild garden warblers (Sylvia Borin) captured at a stopover site. Further, we manipulated blood concentrations of ghrelin to test its effects on food intake and migratory restlessness. We found that acylated ghrelin concentrations of garden warblers with larger fat scores were higher than those of birds without fat stores. Further, injections of unacylated ghrelin decreased food intake and increased migratory restlessness. These results represent experimental evidence that appetite-regulating hormones control migratory behavior. Our study lays a milestone in migration physiology because it provides the missing link between ecologically dependent factors such as condition and timing of migration. In addition, it offers insights in the regulation of the hormonal system controlling food intake and energy stores in vertebrates, whose disruption causes eating disorders and obesity.
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Access to water affects the condition dependency of nocturnal restlessness in Garden Warblers on a Mediterranean island stopover
Journal of Ornithology, 2015Co-Authors: Megan M. Skrip, Ulf Bauchinger, Wolfgang Goymann, Leonida Fusani, Scott R. McwilliamsAbstract:During migration, many songbirds encounter large ecological barriers, like deserts and seas that require substantial fuel to cross and can lead to dehydration during passage. If muscle is not catabolized to generate metabolic water, birds must seek free water on a subsequent stopover to replenish the water lost. Yet, no work has examined if birds crossing large migration barriers use access to free water in concert with energy or protein stores to make stopover decisions. We captured 61 free-living Garden Warblers (Sylvia Borin) in spring at a frequently used stopover site in the Mediterranean Sea, housed them with or without drinking water, and measured nocturnal rest- lessness (Zugunruhe) in relation to energy stores at capture. Both groups lost equivalent flight muscle mass overnight, suggesting that water-deprived birds did not preferentially catabolize this tissue to produce metabolic water. Fat score and body mass, but not flight muscle mass, were positively correlated with nocturnal activity in both treatment groups. However, the slope of the relationship between nocturnal activity and fat score differed between groups, with water- deprived birds of high fat score showing the highest Zu- gunruhe activity. Our results suggest that birds with large energy stores use access to drinking water to inform their decisions about when to depart from a stopover site. Indi- viduals with higher fat scores might be expected, regardless of flight muscle size, to depart a dry stopover site more readily than a site with freely available water. We suggest follow-up studies to further elucidate the mechanisms of this phenomenon and establish its prevalence in free-living birds.
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Condition-Dependent Nocturnal Hypothermia in Garden Warblers Sylvia Borin at a Spring Stopover Site
Ardea, 2014Co-Authors: Marco Cianchetti Benedetti, Leonida Fusani, Massimiliano Cardinale, Roberto Bonanni, Claudio CarereAbstract:Migratory birds have evolved physiological and behavioural adaptations for crossing large ecological barriers through the accumulation of large amounts of fat and protein during the pre-migratory phase. Nevertheless, most migrant passerines usually need several stopovers en route to replenish their energy reserves and to rest. Migratory decisions at a stopover site strongly depend on body condition at arrival. Previous studies showed that lean birds prolong their stopover compared with fat birds that leave after a very short time. During the stopover, lean birds may reduce their metabolic costs by lowering body temperature (adaptive hypothermia hypothesis). However, it is not clear whether hypothermia can be an active economising strategy or just an unavoidable consequence of bad condition to avoid starvation. We used temperature loggers to measure skin temperature of 19 Garden Warblers Sylvia Borin caught at a spring stopover site (Ponza Island, Tyrrhenian Sea) and kept overnight in cotton bags. We found...
Herbert Biebach - One of the best experts on this subject based on the ideXlab platform.
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time place learning by garden warblers Sylvia Borin route or map
Ethology, 2010Co-Authors: John R Krebs, Herbert BiebachAbstract:1 Garden warblers are able to learn to go to four different feeding places at different times of day (time-place learning). We investigated whether or not the birds rely on a fixed route by preventing them from entering one of the places at the normal time (blocking experiments). At the end of the blocking period the birds were allowed to visit any of the four feeding places. 2 In two such blocking experiments, one in which the blocking period was first thing in the morning (from 06.00–10.00 h), the other in which it was later in the day (from 12.00–16.00 h), there was no subsequent shift in the phase of visiting the places during the rest of the day, apart from a tendency to go to the first place of the day after the morning block. These results suggest that the birds do not rely on following a fixed route, but instead use a time-place map.
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Migratory stopover conditions affect the developmental state of male gonads in garden warblers (Sylvia Borin)
Hormones and behavior, 2008Co-Authors: Ulf Bauchinger, Thomas J. Van't Hof, Herbert BiebachAbstract:Long-distance migrants face the challenge of a short window for reproduction that requires optimal timing and full functional gonads. Male garden warblers (Sylvia Borin) meet these demands by initiating testicular recrudescence during spring migration, enabling them to reproduce immediately after arrival at the breeding grounds. In a combined field and laboratory study, we investigated testicular size, plasma levels of luteinizing hormone (LH), androstenedione (AE), 5α-dihydrotestosterone (DHT), testosterone and nocturnal migratory restlessness (Zugunruhe) under different stopover conditions. We manipulated food availability, the duration of stopover and simulated migration by food deprivation. Garden warblers showed significantly retarded testicular development after nine days of stopover under limited food conditions compared to birds that had ad libitum access to food. However, there was no significant difference in Zugunruhe between the two groups. Thus, the degree of Zugunruhe was unaffected by the quality of the stopover site and migration continued independent of the developmental state of the testis. We suggest that male garden warblers face the necessity to either compensate for slowed testicular recrudescence during the subsequent leg of migration and delay arrival at the breeding grounds, or arrive with less developed testes. Either of these may reduce annual reproductive success.
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flexible remodeling of organ size during spring migration of the garden warbler Sylvia Borin
Zoology, 2005Co-Authors: Ulf Bauchinger, Anke Wohlmann, Herbert BiebachAbstract:Abstract The energetic demands of long-distance migratory birds change drastically, depending on the stage of their life cycle. Changing demands are reflected in the up and down regulation of adipose tissue and organ mass. This paper presents new data on organ size changes during different stages of spring migration of garden warblers ( Sylvia Borin ). Phenotypic mass changes were quantified in 13 organs of birds caught in Tanzania, Ethiopia and Egypt. We also sampled birds after a simulated stopover in Egypt. Some organs increased in mass up to about 1.5-fold during migration from Tanzania to Ethiopia, while some remained unchanged or even decreased in mass. During flight across the Sahara, nearly all organ masses including heart and flight muscles were reduced. Exceptionally large reductions (∼50%) were observed for liver, bile, spleen, kidney and digestive tract organs. The only exceptions were the testes, which increased 4-fold in mass. During the simulated stopover in Egypt, a significant recovery was observed for kidney, liver, heart, proventriculus, and small intestine. The testes continued to increase in mass. Flexible remodeling of organ size in the course of spring migration thus comprises significant changes for all quantified organs, with a variety of organ-specific patterns. Individual organ patterns are differentially shaped by functional aspects according to the different organ requirements in the alternation of flight and stopover phases, energetics, future demands, and protein requirements. Anticipatory mechanisms account for the size change of the testes, and we suggest the same for the kidney and the gall bladder.
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energetic savings by organ adjustment during long migratory flights in garden warblers Sylvia Borin
2003Co-Authors: Herbert Biebach, Ulf BauchingerAbstract:During the migratory period, birds are confronted with many physiological challenges that may change dramatically in short succession. Flight phases with voluntary anorexia and simultaneous high metabolic turnover for flight are interrupted by stopover phases with intense foraging behaviour and high intake and processing of food. Functionally, the digestive system plays the important role during stopover and becomes irrelevant during flight. On the other hand, exercise organs have an inverse role, being highly active during flight but much less so during stopover. In the course of migration, these temporary functional differences are reflected in phenotypic organ changes (Piersma and Lindstrom 1997; Biebach 1998; Mc Williams and Karasov 2001). Several hypotheses have been put forward to explain the costs and benefits of this functional and structural flexibility, some of which are not mutually exclusive (Bauchinger and Biebach 1998). Here, we present data on structural changes in the digestive system, the leg muscles, the liver and the exercise organs — such as the flight and heart muscles — of garden warblers (Sylvia Borin) during the long flight across the Sahara desert within one season during spring 1998. The benefits of these structural adjustments are estimated quantitatively with respect to the energetic savings during flight.
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spleen size variation during long distance migration in the garden warbler Sylvia Borin
2002Co-Authors: Charlotte Deerenberg, Herbert Biebach, Ulf BauchingerAbstract:Long-distance migratory passerines show extreme flexibility in body and organ mass in adaptation to the demands of their annual spring and autumn migrations. The extent of observed mass changes commonly entails temporary organ dysfunction. We collected garden warblers Sylvia Borin at various phases during their spring and autumn migration in order to explore a potential trade-off between investment in migration and immune function by examining spleen size. The avian spleen is the principal organ for resistance to disease and parasitic infection in birds and spleen size is assumed to be reflective of immune activity, especially antibody production. If spleen size indeed reflects spleen function, and thus immune activity, there may be a trade-off between immune function and migration, both during the migratory flight itself when there is no nutritional intake, as well as during the stopover phase when depleted tissues necessary to continue migration are being restored. Spleen mass remained at the low level observed immediately after a flight across a major ecological barrier, in contrast to both body mass and other organ masses, which were readily restored during stopover. Clear benefits of a reduced spleen are most likely to occur if spleen maintenance and
Franz Bairlein - One of the best experts on this subject based on the ideXlab platform.
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garden warbler Sylvia Borin detect carotenoids in food but differ strongly in individual food choice
Journal of Ornithology, 2011Co-Authors: Carlo Catoni, Benjamin Metzger, Martin H Schaefer, Franz BairleinAbstract:The concept of optimal foraging has been used to show how animals can increase their fitness by actively regulating the ingestion of nutrients or by avoiding detrimental plant metabolites, such as alkaloids. There is, however, considerably less information available on whether and, if so, how animals actively select beneficial secondary compounds, such as dietary antioxidants. In the last two decades, carotenoids have been the most intensively studied dietary antioxidants in behavioural ecology, and the expression of carotenoid-based ornamentation has become a model for studying the condition dependence of sexually selected traits. In a series of experiments in which we offered individual Garden Warblers (Sylvia Borin) a choice between two foods, one with and one without carotenoids, we found that individual birds did not select food for the maximum amount of carotenoids, rather they choose for a highly consistent carotenoid intake during the course of different dual-choice experiments in which the food offered differed in carotenoid content. However, it remains unclear whether the individual birds were able to optimise their carotenoid intake and, therefore, the expression of life history traits—even though individuals differed consistently in their carotenoid intake. In particular, females tended to avoid food with high carotenoid contents. Based upon the highly consistent carotenoid intake of individual birds, we conclude that our birds were able to perceive the presence of carotenoids in the food without the use of visual cues. We suggest that these results may shed new light on the mechanisms that birds may use to regulate the ingestion of these antioxidants and, consequently, possibly affect the expression of life history traits, such as immunocompetence or sexually selected traits.
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isotopic fractionation and turnover in captive garden warblers Sylvia Borin implications for delineating dietary and migratory associations in wild passerines
Canadian Journal of Zoology, 2003Co-Authors: Keith A Hobson, Franz BairleinAbstract:There is currently a great deal of interest in using stable-isotope methods to investigate diet and migratory connections in wild passerines. To apply these methods successfully, it is important to...
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the autumnal fattening of the long distance migratory garden warbler Sylvia Borin is stimulated by intermittent fasting
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2000Co-Authors: U Totzke, A Hubinger, J Dittami, Franz BairleinAbstract:To investigate the proximate influence of a changing food availability on the seasonal fattening of migratory birds, garden warblers (Sylvia Borin) following postnuptial moult were food restricted once a week. Body mass, food intake, plasma hormone and metabolite levels were measured and compared to birds which always had ad libitum food access. The food-restricted birds increased their body mass significantly earlier than the controls. The accelerated fattening was initially not accompanied by hyperphagia and may be due to either an increased food utilisation efficiency or a reduced metabolic rate. An increase of basal glucagon and corticosterone and a decrease of insulin levels prior to fattening were not significant, however, they resulted in a significant decrease of the insulin:glucagon ratio. This ratio was also lower in food-restricted birds than in control birds and may account for the difference in the fattening progress. We conclude that seasonal fattening may be stimulated by a catabolic impulse which could be imposed in free-living birds by a decrease of food availability and/or by an increase of energy expenditure. A negative energy balance is hypothesised to be a common proximate factor affecting migratory as well as winter fattening.
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fasting increases the plasma glucagon response in the migratory garden warbler Sylvia Borin
General and Comparative Endocrinology, 1999Co-Authors: Uwe Totzke, Achim Hubinger, Gerda Korthaus, Franz BairleinAbstract:Abstract Acute pancreatic hormonal responses to oral glucose loads were investigated in garden warblers during the prolonged fast that follows their autumnal migratory fattening. Plasma glucose, free fatty acids, β-hydroxybutyrate, insulin (INS), and glucagon (GLN) were measured prior to and 10 min after an oral glucose load in three groups of birds: One had food ad libitum, and the other two were either food restricted or food deprived down to a given (low) body mass level. Ten minutes after the glucose load, plasma glucose levels increased significantly in all three groups (range of mean values: basal, 15.1–16.0; glucose-stimulated, 19.1–23.7 mmol/L). A smaller increase in food-restricted/deprived groups was not statistically significant. Free fatty acid levels (1.0–1.5 mmol/L) after 10 min were unchanged, while β-hydroxybutyrate decreased to similar levels in food-restricted/deprived and control groups (basal, 3.3–4.2; glucose-stimulated, 1.9–2.4 mmol/L). Insulin increased and glucagon decreased in response to oral glucose loads. However, initial levels and responses of plasma insulin to glucose were lower, and those of glucagon were higher in the food-restricted/deprived groups (INS, both 2.7; ΔINS, 0.1–0.3 mIU/L; GLN, 2.8–3.3; ΔGLN, 1.4–2.2 μg/L) than in the control group (means ± SE; INS, 3.8 ± 0.8; ΔINS, 1.4 ± 0.7 mIU/L; GLN, 2.5 ± 0.5; ΔGLN, 0.7 ± 0.5 μg/L), resulting in similar increases in the insulin:glucagon ratio. Impaired insulin secretion may thus be compensated for by a greater glucagon response and the decreased glucose utilization rates of fasting garden warblers may result from insulin resistance and/or delayed glucose absorption.
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the effect of diet composition on migratory fuelling in garden warblers Sylvia Borin
Journal of Avian Biology, 1998Co-Authors: Franz BairleinAbstract:Prior to migration, many migratory birds accumulate large stores of lipids as the prime energy for their migratory flights. Although this phenomenon is well known, comparatively little is known about the mechanisms of fat accumulation, and the nutritional demands and nutritional adaptations of fattening migrants. This paper shows recent findings on the role of nutrients in fattening, and how migrants are likely to achieve optimal rates of fattening by diet selection. Dietary energy and nutrient composition of foods clearly influenced the rate of daily body mass gain during migratory fattening. However, it was neither energy nor a single nutrient alone which accounted for migratory fattening. Most of the variation in body mass gain was explained by the combined effects of high energy intake, where the energy was provided by fat, and by protein intake, whereas the role of carbohydrates is less clear. The data are discussed with respect to the adaptive role of seasonal shifts in diet selection during fattening periods known for many species, and the consequences of diet for fat deposition time, fat deposition rates, and fat loads at departure as major predictors in optimal migration models.
Michael Widmer - One of the best experts on this subject based on the ideXlab platform.
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are long distance migrants constrained in their evolutionary response to environmental change causes of variation in the timing of autumn migration in a blackcap s atricapilla and two garden warbler Sylvia Borin populations
Annals of the New York Academy of Sciences, 2005Co-Authors: Francisco Pulido, Michael WidmerAbstract:Long-distance migratory birds often show little phenotypic variation in the timing of life-history events like breeding, molt, or migration. It has been hypothesized that this could result from low levels of heritable variation. If this were true, the adaptability of long-distance migratory birds would be limited, which would explain the vulnerability of this group of birds to environmental changes. The amount of phenotypic, environmental, and genetic variation in the onset of autumn migratory activity was assessed in two garden warbler (Sylvia Borin) populations differing in breeding phenology and the length of the breeding season with the aim of investigating the effects of selection on the adaptability of long-distance migrants. High heritabilities and additive genetic variance components for the timing of autumn migration were found in both populations. Although genetic variation in the mountain population was lower than in the lowlands, this difference was not statistically significant. Moreover, no evidence was found for reduced levels of genetic variation in the garden warbler as compared to its sister species, the blackcap (S. atricapilla). Environmental variation, however, was markedly reduced in the garden warbler, suggesting that low levels of phenotypic variation typically found in long-distance migrants may be a consequence of environmental canalization of migratory traits. The buffering of environmental variation may be an adaptive response to strong stabilizing selection on the timing of migration. High environmental canalization of migration phenology in long-distance migrants could potentially explain low rates of immediate phenotypic change in response to environmental change.
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Are long-distance migrants constrained in their evolutionary response to environmental change? Causes of variation in the timing of autumn migration in a blackcap (S-atricapilla) and two garden warbler (Sylvia Borin) populations
Annals of the New York Academy of Sciences, 2005Co-Authors: Francisco Pulido, Michael WidmerAbstract:Long-distance migratory birds often show little phenotypic variation in the timing of life-history events like breeding, molt, or migration. It has been hypothesized that this could result from low levels of heritable variation. If this were true, the adaptability of long-distance migratory birds would be limited, which would explain the vulnerability of this group of birds to environmental changes. The amount of phenotypic, environmental, and genetic variation in the onset of autumn migratory activity was assessed in two garden warbler (Sylvia Borin) populations differing in breeding phenology and the length of the breeding season with the aim of investigating the effects of selection on the adaptability of long-distance migrants. High heritabilities and additive genetic variance components for the timing of autumn migration were found in both populations. Although genetic variation in the mountain population was lower than in the lowlands, this difference was not statistically significant. Moreover, no evidence was found for reduced levels of genetic variation in the garden warbler as compared to its sister species, the blackcap (S. atricapilla). Environmental variation, however, was markedly reduced in the garden warbler, suggesting that low levels of phenotypic variation typically found in long-distance migrants may be a consequence of environmental canalization of migratory traits. The buffering of environmental variation may be an adaptive response to strong stabilizing selection on the timing of migration. High environmental canalization of migration phenology in long-distance migrants could potentially explain low rates of immediate phenotypic change in response to environmental change. [KEYWORDS: heritability ; zugunruhe ; climate change ; adaptation ; canalization]
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phanologie siedlungsdichte und populationsokologie der gartengrasmucke Sylvia Borin in einem subalpinen habitat der zentralalpen
Journal of Ornithology, 1996Co-Authors: Michael WidmerAbstract:A population of Garden Warbler was studied in a natural habitat in the Urseren valley (1500 m a. s. l.) for 7 years. The aim of this study was to describe the migration phenology and to evaluate if a self-sustainable population of this long distance migrant can exist under unfavourable climatic conditions. In spring, the Garden Warblers arrive about 3 weeks later, but in late summer they leave their territories at the same time as their conspecifics in the lowlands. Possible consequences of the restricted breeding period for juvenile development and migration schedule are discussed. In the study area, a very high breeding density (25 territories/10 ha) was recorded. The birds show a remarkable breeding and natal site fidelity (48 % of adults and 6 % of nestlings returned the following year). The overall breeding success was 48 %. The main causes of failure were predation and bad weather events. The latter were responsible for the annual fluctuations of breeding success. In conclusion, this study confirms that self-sustainable populations of this long-distance migratory species exist in mountain habitats.
Wolfgang Goymann - One of the best experts on this subject based on the ideXlab platform.
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Effects of body condition and food intake on stop-over decisions in Garden Warblers and European Robins during spring migration
Journal of Ornithology, 2017Co-Authors: Sara Lupi, Wolfgang Goymann, Massimiliano Cardinale, Alfonso Rojas Mora, Ivan Maggini, Leonida FusaniAbstract:During migration, birds need to optimize their time and/or energy management, especially during stop-overs. Previous studies with caged birds under controlled condition support the notion that departure decisions are condition-dependent, but they did not take into account the availability or the actual intake of food. In the study reported here we investigated whether food intake interacts with condition in influencing migratory disposition in temporarily caged wild migrants. We conducted the study on Garden Warblers (Sylvia Borin) and European Robins (Erithacus rubecula) at a spring stop-over site that is reached after a long non-stop flight over the Mediterranean Sea. The birds were held in cages during the day and the first night following capture, and their locomotor activity, food intake, and body mass change were recorded. In both species, food intake was positively correlated with body mass change. Body condition was positively correlated with migratory restlessness (Zugunruhe) in both species and was also negatively related to diurnal activity in Garden Warblers. Food intake was negatively correlated with diurnal activity in Garden Warblers. When only birds with low fat scores were considered, we found a positive effect of food intake on Zugunruhe in Garden Warblers. In general, European Robins consumed less food than Garden Warblers and no significant effects on Zugunruhe were found. Our results show that food intake interacts with condition in affecting migratory behavior during stop-overs. In particular, food intake may induce Garden Warblers with low fat stores at arrival to leave a stop-over site earlier. The large individual variability in food consumption supports the notion that birds vary in their capacity to refuel soon after arrival at a stop-over site. Overall, our work suggests that the decision to stay at the stop-over site or to resume migration depends on the interaction of condition, refueling capacity and rate, and migratory strategy.
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ghrelin affects stopover decisions and food intake in a long distance migrant
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Wolfgang Goymann, Sara Lupi, Massimiliano Cardinale, Hiroyuki Kaiya, Leonida FusaniAbstract:Abstract Billions of birds migrate long distances to either reach breeding areas or to spend the winter at more benign places. On migration, most passerines frequently stop over to rest and replenish their fuel reserves. To date, we know little regarding how they decide that they are ready to continue their journey. What physiological signals tell a bird’s brain that its fuel reserves are sufficient to resume migration? A network of hormones regulates food intake and body mass in vertebrates, including the recently discovered peptide hormone, ghrelin. Here, we show that ghrelin reflects body condition and influences migratory behavior of wild birds. We measured ghrelin levels of wild garden warblers (Sylvia Borin) captured at a stopover site. Further, we manipulated blood concentrations of ghrelin to test its effects on food intake and migratory restlessness. We found that acylated ghrelin concentrations of garden warblers with larger fat scores were higher than those of birds without fat stores. Further, injections of unacylated ghrelin decreased food intake and increased migratory restlessness. These results represent experimental evidence that appetite-regulating hormones control migratory behavior. Our study lays a milestone in migration physiology because it provides the missing link between ecologically dependent factors such as condition and timing of migration. In addition, it offers insights in the regulation of the hormonal system controlling food intake and energy stores in vertebrates, whose disruption causes eating disorders and obesity.
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Access to water affects the condition dependency of nocturnal restlessness in Garden Warblers on a Mediterranean island stopover
Journal of Ornithology, 2015Co-Authors: Megan M. Skrip, Ulf Bauchinger, Wolfgang Goymann, Leonida Fusani, Scott R. McwilliamsAbstract:During migration, many songbirds encounter large ecological barriers, like deserts and seas that require substantial fuel to cross and can lead to dehydration during passage. If muscle is not catabolized to generate metabolic water, birds must seek free water on a subsequent stopover to replenish the water lost. Yet, no work has examined if birds crossing large migration barriers use access to free water in concert with energy or protein stores to make stopover decisions. We captured 61 free-living Garden Warblers (Sylvia Borin) in spring at a frequently used stopover site in the Mediterranean Sea, housed them with or without drinking water, and measured nocturnal rest- lessness (Zugunruhe) in relation to energy stores at capture. Both groups lost equivalent flight muscle mass overnight, suggesting that water-deprived birds did not preferentially catabolize this tissue to produce metabolic water. Fat score and body mass, but not flight muscle mass, were positively correlated with nocturnal activity in both treatment groups. However, the slope of the relationship between nocturnal activity and fat score differed between groups, with water- deprived birds of high fat score showing the highest Zu- gunruhe activity. Our results suggest that birds with large energy stores use access to drinking water to inform their decisions about when to depart from a stopover site. Indi- viduals with higher fat scores might be expected, regardless of flight muscle size, to depart a dry stopover site more readily than a site with freely available water. We suggest follow-up studies to further elucidate the mechanisms of this phenomenon and establish its prevalence in free-living birds.
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Food availability but not melatonin affects nocturnal restlessness in a wild migrating passerine.
Hormones and behavior, 2010Co-Authors: Leonida Fusani, Massimiliano Cardinale, Ingrid Schwabl, Wolfgang GoymannAbstract:A large number of passerine species migrate at night, although most of them are diurnal outside the migratory seasons. This diurnal-to-nocturnal transition is a major life-history event, yet little is known about its physiological control. Previous work showed that during the migratory periods captive birds showing nocturnal migratory restlessness (Zugunruhe) have reduced concentrations of circulating melatonin at night compared to non-migratory periods. This suggested that the hormone melatonin, a main component of the avian circadian system, is involved in the expression of Zugunruhe. Other studies demonstrated that the relationship between low melatonin levels and Zugunruhe is not a seasonal correlation. When Zugunruhe was interrupted by exposing birds to a fasting-and-refeeding protocol, melatonin levels increased. Here we studied whether melatonin and food availability influence the intensity of Zugunruhe in wild migrating garden warblers (Sylvia Borin) at a stopover site. Birds were held in recording cages overnight, with or without food available, and either bled to determine melatonin concentrations or treated transdermally with melatonin. We found that melatonin levels at night were correlated with the intensity of diurnal locomotor activity and with condition, but were not correlated with Zugunruhe. Similarly, the melatonin treatment did not have effects on Zugunruhe, whereas food availability increased it. Our study shows that the nocturnal melatonin levels in migrating warblers depend on food availability and are correlated with condition. In addition, it suggests that melatonin does not control Zugunruhe and might rather be involved in energy conservation and/or clock synchronization during migration.
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body fat influences departure from stopover sites in migratory birds evidence from whole island telemetry
Biology Letters, 2010Co-Authors: Wolfgang Goymann, Fernando Spina, Andrea Ferri, Leonida FusaniAbstract:Migration remains one of the great mysteries of animal life. Small migratory birds rely on refuelling stopovers after crossing ecological barriers such as deserts or seas. Previous studies have suggested that fuel reserves may determine stopover duration but this hypothesis could not be tested because of methodological limitations. Here, we provide evidence that subcutaneous fat stores determine stopover duration by measuring the permanence of migratory garden warblers (Sylvia Borin) on a small Mediterranean island during spring migration with telemetry methods. Garden warblers with large amounts of fat stores departed the island significantly sooner than lean birds. All except one fat bird left the island on the same evening after capture, with a mean total stopover estimate of 8.8 hours. In contrast, the mean estimated total stopover duration of lean birds was 41.3 hours. To our knowledge, this is the first study that measures the true minimum stopover duration of a songbird during migration.
