Phenotypic flexibility of body composition in relation to migratory state,age, and sex in the western sandpiper (Calidris mauri)

We investigated the flexibility of body composition in relation to seasonally variable demands for endurance flight capacity and hyperphagia in a migratory shorebird. Migrating western sandpipers were sampled in spring and fall while refueling at a north temperate stopover and were compared with nonmigrating birds captured at a tropical wintering area in Panama. Sandpipers weighed 25% more at stopover, and nearly 40% of migratory mass increase consisted of lean body components. Most organs and flight muscles were 10%-100% larger during migration, and the greatest relative size increases occurred in the digestive system (including liver). Birds preparing to initiate spring migration from Panama deposited only fat, suggesting that changes in lean body components take place after migration has begun, possibly through training effects. Sex did not influence body composition. Juveniles making their first southward migration were similar to adults in structural size and body mass but had substantially enlarged alimentary tracts. Sandpipers appeared to deposit lean mass during stopover in fall but not in spring. The dramatic enlargement of the digestive system in this small species that makes short flights and fuels frequently contrasts with the reduction of digestive components in larger species that fuel only once or twice by making one or two very long flights to their destination.     

Is long-distance bird flight equivalent to a high-energy fast? Body composition changes in freely migrating and captive fasting great knots

We studied changes in body composition in great knots, Calidris tenuirostris, before and after a migratory flight of 5,400 km from northwest Australia to eastern China. We also took premigratory birds into captivity and fasted them down to their equivalent arrival mass after migration to compare organ changes and nutrient use in a low-energy-turnover fast with a high-energy-turnover fast (migratory flight). Migrated birds were as economical as any fasting animal measured yet at conserving protein: their estimated relative protein contribution (RPC) to the energy used was 4.0%. Fasted birds had an estimated RPC of 6.8% and, consequently, a much lower lean mass and higher fat content for an equivalent body mass than migrated birds. Lean tissue was catabolized from most organs in both groups, except the brain. Furthermore, a principal components biplot showed that individuals were grouped primarily on the basis of overall organ fat or lean tissue content rather than by the size of specific organs. This indicates that organ changes during migratory flight are similar to those of a low-energy fast, although the length of the fast in this study probably accentuated organ reductions in some functional groups. Whether the metabolic characteristics of a flying migratory fast follow the three-phase model described in many inactive fasting animals is unclear. We have some evidence for skeletal fat being catabolized without phase 3 of a fast having been reached.     

Empirical evidence for differential organ reductions during trans-oceanic bird flight

Since the early 1960s it has been held that migrating birds deposit and use only fat as fuel during migratory flight, with the non-fat portion of the body remaining homeostatic. Recent evidence from field studies has shown large changes in organ sizes in fuelling birds, and theory on fuel use suggests protein may be a necessary fuel during flight. However, an absence of information on the body condition of migrants before and after a long flight has hampered understanding of the dynamics of organs during sustained flight. We studied body condition in a medium-sized shorebird, the great knot (Calidris tenuirostris), before and after a flight of 5400 km from Australia to China during northward migration. Not only did these birds show the expected large reduction in fat content after migration, there was also a decrease in lean tissue mass, with significant decreases in seven organs. The reduction in functional components is reflected in a lowering of the basal metabolic rate by 42% [corrected]. Recent flight models have tried to separate the 'flexible' part of the body from the constant portion. Our results suggest that apart from brains and lungs no organs are homeostatic during long-distance flight. Such organ reductions may be a crucial adaptation for long-distance flight in birds.     

Early life events carry over to influence pre-migratory condition in a free-living songbird

Conditions experienced during development can have long-term consequences for individual success. In migratory songbirds, the proximate mechanisms linking early life events and survival are not well understood because tracking individuals across stages of the annual cycle can be extremely challenging. In this paper, we first use a 13 year dataset to demonstrate a positive relationship between 1(st) year survival and nestling mass in migratory Savannah sparrows (Passerculus sandwichensis). We also use a brood manipulation experiment to show that nestlings from smaller broods have higher mass in the nest relative to individuals from larger broods. Having established these relationships, we then use three years of field data involving multiple captures of individuals throughout the pre-migratory period and a multi-level path model to examine the hypothesis that conditions during development limit survival during migration by affecting an individual's ability to accumulate sufficient lean tissue and fat mass prior to migration. We found a positive relationship between fat mass during the pre-migratory period (Sept-Oct) and nestling mass and a negative indirect relationship between pre-migratory fat mass and fledging date. Our results provide the first evidence that conditions during development limit survival during migration through their effect on fat stores. These results are particularly important given recent evidence showing that body condition of songbirds at fledging is affected by climate change and anthropogenic changes to landscape structure.     

Body Composition Characteristics During Puberty in Girls and Boys from Eastern Austria

Puberty represents the final stage of sexual differentiation when the individual acquires reproductive capacity. Puberty is not only characterized by maturation of sexual organs and the formation of oocytes and mature spermatozoa, but also by the development of secondary sexual dimorphism. In industrialized countries, the age of puberty has decreased steadily over the last 150 years in association with improved socio-economic conditions. However, the decreased onset of puberty, especially in females, is associated with problematic changes in behaviour such as early onset of sexual activity resulting in high-risk teenage pregnancies. In our study, we analysed the association between body composition (fat tissue and fat-free body mass, estimated by BIA analyses), height, body mass index and fat distribution and signs of puberty such as the timing of menarche in 228 girls and voice breaking and facial hair growth in 191 boys ageing between 10 and 15 years. In both sexes, signs of puberty were associated, highly significantly, with body composition parameters. Nevertheless, marked differences between the two sexes were observed: Female puberty was positively associated with weight status and the absolute and relative amount of body fat, while in males, puberty was positively related with a higher amount of fat-free body mass and a decreased fat mass. Male voice breaking was significantly associated with increased stature, body weight, waist and hip circumference, lean body mass and total body water. In contrast, voice breaking was significantly negatively associated with the fat percentage, the total fat mass and the waist-to-hip ratio. Female menarche was significantly positively associated with increased body weight, weight status, waist and hip circumference and also with increased absolute and relative fat mass, relative hip circumference, lean body mass and total body water. Only the waist-to-hip ratio was significantly negatively associated with the onset of menarche.     

Non-invasive measure of body composition of snakes using dual-energy X-ray absorptiometry

Non-invasive techniques to measure body composition are critical for longitudinal studies of energetics and life histories and for investigating the link between body condition and physiology. Previous attempts to determine, non-invasively, the body composition of snakes have proven problematic. Therefore, we explored whether dual-energy X-ray absorptiometry (DXA) could be used to determine the body composition of snakes. We analyzed 20 adult diamondback water snakes (Nerodia rhombifer) with a DXA instrument and subsequently quantified their body composition by gravimetric and chemical extraction methods. Body composition components scaled with body mass with mass exponents between 0.88 and 1.53. DXA values for lean tissue mass, fat mass and total-body bone mineral mass were significantly correlated with observed masses of lean tissue, fat and ash from chemical analysis. Using regression models incorporating DXA values we predicted the fat-free tissue mass, lean tissue mass, fat mass, ash mass and total body water content for this sample of water snakes. A cross-validation procedure demonstrated that these models estimated fat-free tissue mass, lean tissue mass, fat mass, ash mass and total-body water content with respective errors of 2.2%, 2.3%, 16.0%, 6.6% and 3.5%. Compared to other non-invasive techniques, include body condition indices, total body electrical conductivity (TOBEC) and cyclopropane absorption, DXA can more easily and accurately be used to determine the body composition of snakes.     

Female butterflies modulate investment in reproduction and flight in response to monsoon‐driven migrations

Migratory species may display striking phenotypic plasticity during individual lifetimes. This may include differential investment in body parts and functions, differential resource use and allocation, and behavioural changes between migratory and non‐migratory phases. While migration‐related phenotypic changes are well‐reported, their underlying mechanisms are usually poorly understood. Here we compare individuals from migratory (reproductive diapause) and non‐migratory (reproductive) phases of closely related aposematic butterfly species to study how sexual dimorphism and migratory behaviour underlie significant morphological tradeoffs, and propose a plausible scenario to explain the migration‐related phenotypic plasticity observed in females of migratory species. We found that female butterflies invested significantly more in their abdominal mass compared to males irrespective of their migratory phase, and underwent a clear shift in their body mass allocation after the switch from the reproductive diapause phase to the reproductive phase. In reproductive phase, females invested much more in reproductive tissue. This switch occurred as a result of increased abdominal mass (i.e. reproductive tissue mass) without significant reduction in the thoracic mass (i.e. flight muscle mass). Migratory males, however, were not significantly different from non‐migratory males in terms of relative investment in flight and reproductive tissues. These patterns were consistent between migratory and non‐migratory aposematic species within and across clades. While migratory habits may influence the physiology and behaviour of both sexes, long‐distance migration affected female morphology much more markedly compared to that of males. These results show the sex‐specific nature of adaptations to migratory behaviour, and suggest that seemingly disparate life‐history traits such as aposematism and migration may have similar influences on the lifetime energetic investments of insects.     

Relations among measures of body composition, age, and sex in the common marmoset monkey (Callithrix jacchus)

Few studies of body composition have been done in New World primates. In the study reported here, four methods of assessing body composition (body weight, anthropometry, labeled-water dilution, and total body electroconductivity) were compared in 20 marmosets, aged 0.96 to 7.97 years. Males and females did not differ in any measure (P > 0.05). Body weight ranged from 272 to 466 g, and body fat estimates varied from 1.6 to 19.5%. Strong positive correlations were observed between total body water and total body electroconductivity (R2 = 0.77), body weight and fat-free mass (males R2 = 0.95; females R2 = 0.91), and body weight and fat mass (males R2 = 0.86; females R2 = 0.85; P < 0.01). Male and female slopes were equivalent (P > 0.05) for the regressions of fat and fat-free mass against body weight. Positive correlations also were observed between girth measures and fat-free mass (R2 = 0.48 to 0.78) and fat mass (R2 = 0.60 to 0.74; P < 0.01). A good second- order polynomial relationship was observed between age and fat-free mass for the combined sample (R2 = 0.64). Results indicated that: subjects were lean; there was no sexual dimorphism relative to measures; body weight provided a reliable estimate of fat and fat-free mass; and within-subject body weight changes reflected a similar relationship between body weight and fat-free mass as did that across subjects.     

Human Body Composition and the Epidemiology of Chronic Disease

Obesity and body fat distribution (FD) are established risk factors for chronic diseases. The body mass index (BMI) and the waist/hip circumference ratio (WHR) are used conventionally as indices of obesity and FD in epidemiological studies. Although some general limitations of these indices are recognized, others that affect their use in relative risks for disease are not well recognized. These include effects of sex, ethnicity, and especially age on the relationships between these indices and body composition, which can result in substantial misclassification of obesity and FD. There is considerable variability in body composition for any BMI, and some individuals with low BMIs have as much fat as those with high BMIs. This results in poor sensitivity for classifying levels of body fatness (e.g., too many “false negatives,” or overweight individuals classified as not overweight), and relative risks are attenuated across all categories of BMI. A more serious problem, however, is that at different ages the same levels of BMI correspond to different amounts of fat and fat-free mass. Data from the Rosetta Study and the New Mexico Aging Process Study show that older adults have, on average, more fat than younger adults at any BMI, due to the loss of muscle mass with age. As a result, the sensitivity of BMI cutpoints with respect to body fatness decreases with age, and the use of a fixed cutpoint for all ages results in “differential mis-classification bias.” Taken together, these issues sug- gest that the increases with age in the prevalences of overweight and obesity, and in the risks for chronic diseases, may be mis-estimated using BMI. Similar issues may affect the use of WHR for estimating prevalences and associated risks of FD. New field methods for estimating body composition are available that can be applied in large, epidemiologic follow-up studies of chronic diseases. These methods will allow epidemiologists to consider, for example, whether it is increased fat, or the replacement of fat-free mass with fat, with age that is associated with risk for chronic disease.     

Pointed wings, low wingloading and calm air reduce migratory flight costs in songbirds

Migratory bird, bat and insect species tend to have more pointed wings than non-migrants. Pointed wings and low wingloading, or body mass divided by wing area, are thought to reduce energy consumption during long-distance flight, but these hypotheses have never been directly tested. Furthermore, it is not clear how the atmospheric conditions migrants encounter while aloft affect their energy use; without such information, we cannot accurately predict migratory species' response(s) to climate change. Here, we measured the heart rates of 15 free-flying Swainson's Thrushes (Catharus ustulatus) during migratory flight. Heart rate, and therefore rate of energy expenditure, was positively associated with individual variation in wingtip roundedness and wingloading throughout the flights. During the cruise phase of the flights, heart rate was also positively associated with wind speed but not wind direction, and negatively but not significantly associated with large-scale atmospheric stability. High winds and low atmospheric stability are both indicative of the presence of turbulent eddies, suggesting that birds may be using more energy when atmospheric turbulence is high. We therefore suggest that pointed wingtips, low wingloading and avoidance of high winds and turbulence reduce flight costs for small birds during migration, and that climate change may have the strongest effects on migrants' in-flight energy use if it affects the frequency and/or severity of high winds and atmospheric instability.     

Systemic and regional free fatty acid metabolism in type 2 diabetes

To determine whether type 2 diabetes mellitus alters systemic and regional free fatty acid ([3H]palmitate) metabolism, 14 nondiabetic (ND) and 14 type 2 diabetic (D) subjects underwent hyperinsulinemic-hyperglycemic (approximately 9.3 mM) clamps. The subjects were matched for age, body mass index, percent body fat, and fat-free mass. D subjects had more (P < 0.05) visceral fat than ND. During somatostatin, replacement growth hormone, and glucagon infusions, insulin was infused to achieve moderate (approximately 75 pmol/l) and high (approximately 150 pmol/l) physiological insulin levels. D subjects had greater (P < 0.02) systemic and regional (splanchnic and leg) palmitate release than ND subjects during both insulin infusion intervals. The relative contributions of splanchnic, leg, and nonsplanchnic upper body regions to systemic palmitate release did not differ between groups, although the last contributed the most (approximately 75%) to systemic palmitate release. Visceral fat area correlated with systemic palmitate flux (r = 0.45, P < 0.03) during both insulin infusions. We conclude that type 2 diabetes is associated with a generalized impairment in insulin suppression of lipolysis compared with equally obese ND individuals.     

Oxidative damage and anti-oxidant capacity in two migratory bird species at a stop-over site

We quantified in the garden warbler (Sylvia borin) and the barn swallow (Hirundo rustica), two long-distance migratory songbirds, the early oxidative damage (ROMs) and plasma anti-oxidant capacity (OXY) variation of individuals caught at a stop-over site after a sustained flight across the sea, during spring migration. Our main goal was to quantify the oxidative damage and anti-oxidant capacity variation in these two migratory species in relation to fat and muscle stores. The birds were sampled in Ponza, a small island along the migratory route of these species. The levels of ROMs and OXY did not show any differences between the two species and in general were higher in individuals with higher fat and protein stores. Nevertheless, the balance between ROMs and OXY was better in individuals in good condition. These patterns were similar in both species. No sex differences emerged for both ROMs and OXY in the barn swallow, the only species that could be sexed. Both markers of oxidative stress did not show any significant variation across a 30-min restrained experiment. These data are the first of this kind in wild birds in a migratory context and suggest that individuals in better condition are exposed to lower oxidative stress, providing an indirect evidence of the oxidative cost caused by prolonged flights.     

Postpartum changes in body composition

Parity is associated with weight retention and has long-lasting and detrimental effects on the health of women. Previous studies have shown that increasing parity was independently associated with an increased prevalence of metabolic syndrome. Postpartum weight is made up of several components including uterine and mammary tissues, body water (intracellular (ICW) and extracellular water (ECW)), and fat. These components change in variable amounts postpartum, thereby distinctly affecting the interpretation of individual weight retention; however, it is unclear which components contribute to weight retention. The aims of this longitudinal study were to evaluate changes in body composition during the postpartum period and to investigate their effects on weight retention. This prospective study examined 41 healthy, pregnant women who gave birth at Korea University Guro Hospital. We measured body composition at 2 days, 2 weeks, and 6 weeks postpartum using bioelectrical impedance analysis. Weight decreased during this postpartum period (P < 0.001); the postpartum weight retention from prepregnancy to 6 weeks postpartum was 4.43 ± 4.0 kg. Among various body composition components, ECW, ICW, total body water, and fat-free mass (FFM) decreased postpartum. However, fat mass (FM) and visceral fat area, the components that experienced the greatest changes, increased postpartum. Our results demonstrate that the postpartum period is associated with a preferential accumulation of adipose tissue in the visceral compartment, even though overall body weight is decreased. Further studies are needed to evaluate the changes in body composition over longer time periods and their long-term effects on health.     

Patterns and correlates of songbird movements at an ecological barrier during autumn migration assessed using landscape‐ and regional‐scale automated radiotelemetry

Departure decisions of songbirds at ecological barriers they encounter en route can strongly influence time, energy and survival costs of migration. To date, most field studies of departure decisions and their correlates have used indirect methods and followed migrants at a single stopover site, with limited information on what happens to individuals after they depart from the site. We used an automated radiotelemetry array extending 350 km from southwest Nova Scotia to southern Maine to study the migratory and stopover movements of Northern Waterthrushes Parkesia noveboracensis, Red‐eyed Vireos Vireo olivaceus and Yellow‐rumped Warblers Setophaga coronata in relation to fuel load and weather at the northeastern edge of the Gulf of Maine. From the 105 radio‐transmitters we deployed in southwest Nova Scotia, we recorded 42 landscape‐scale stopover flights and 47 migratory flights by 75 individuals. Of the migratory flights, 57% were orientated southwest, a trajectory that, if held, would require individuals to complete a 350–440 km overwater flight. The remaining 43% of migratory flights were orientated northwest, away from the Gulf of Maine, and 15 individuals were confirmed to have detoured around all or a portion of the barrier, as evidenced by their being re‐detected over the Bay of Fundy and/or along the coast of Maine between 4 h and 15 days later. Across all individuals, initial fat score had a positive effect on departure probability, especially for individuals that made stopover flights. Among weather variables, tailwind assistance was the best predictor of migratory departures but did not appear to be the main factor determining whether individuals orientated towards or away from the Gulf of Maine. Weather had little effect on departure decisions of individuals that made stopover flights. These differences in the correlates of migratory departures and stopover flights would probably not have been distinguishable had our study been restricted to a local scale. Therefore, our findings highlight the importance of expanding the scale at which departure decisions and the ecology of stopover in general are studied.     

Variability and size in mammals and birds

Body size, its variability, and their ecological correlates have long been important topics in evolutionary biology. Yet, the question of whether there is a general relationship between size and size-relative variability has not previously been addressed. Through an analysis of body-mass and length measurements from 65 074 individuals from 351 mammalian species, we show that size-relative variability increases significantly with mean species body size. Analysis of mean body mass and standard deviations for 237 species of birds revealed the same pattern. We present three plausible alternatives explanations and eliminate several others. Of these, the hypothesis that the increase in size-relative variability with mean body mass is related to the scaling of body mass components is most strongly supported. In effect, larger mammals and birds are more variable because their body mass is composed to greater relative degree of components with higher intrinsic variability (bone, fat, and muscle). In contrast, smaller mammals and birds have lower body mass variability because they are composed to a greater relative extent of components (viscera and nervous system) in which size variation is more highly constrained by energetic and functional factors.     

The effects of dietary macronutrients on flight ability,energetics, and fuel metabolism of yellow‐rumped warblers Setophaga coronata

The catabolism of protein from organs and muscles during migratory flight is necessary to produce glucose, key metabolic intermediates, and water, but may have negative effects on flight range and refueling at stopovers. We tested the hypothesis, suggested by previous studies, that birds that eat high‐protein insect diets use more protein for fuel in flight than those that eat high‐carbohydrate fruits. First, we fed migratory yellow‐rumped warblers synthetic fruit or mixed insect/fruit diets, and measured metabolic rates and fuel mixture under basal conditions and during exercise in a hop/hover wheel respirometer. Birds eating the fruit diet had greater plasma triglyceride and non‐esterified fatty acid concentrations, and the higher protein mixed diet increased plasma uric acid only during feeding. Diet did not affect metabolic rates or the fuel mixture under resting or exercise conditions. We then fed yellow‐rumped warblers synthetic diets that differed only in the relative proportion of carbohydrate and protein (60:15 versus 15:60 as % dry mass) and tested them in wind tunnel flights lasting up to six hours. Birds fed the high carbohydrate diet became heavier and fatter than when fed the high protein diet. Plasma uric acid concentration was increased and plasma phospholipid concentration was decreased by the high protein diet in the pre‐flight state (after a 3 h fast), but diet only affected plasma phospholipids during flight (lower in high protein birds). Neither diet nor amount of body fat affected the rate of loss of lean mass or fat during flight. Inter‐individual or seasonal differences in diet do not appear to influence the amount of protein catabolized during endurance flight. However, birds fed the high carbohydrate diet had greater voluntary flight duration, independent of body fatness, suggesting that there may be other performance benefits of high carbohydrate diets for migratory birds.     

Body mass and wing shape explain variability in broad-scale bird species distributions of migratory passerines along an ecological barrier during stopover

Migrating birds are under selective pressure to complete long-distance flights quickly and efficiently. Wing morphology and body mass influence energy expenditure of flight, such that certain characteristics may confer a greater relative advantage when making long crossings over ecological barriers by modifying the flight range or speed. We explored the possibility, among light (mass <50 g) migrating passerines, that species with relatively poorer flight performance related to wing shape and/or body mass have a lower margin for error in dealing with the exigencies of a long water crossing across the Gulf of Mexico and consequently minimize their travel time or distance. We found that species-mean fat-free body mass and wing tip pointedness independently explained variability among species distributions within ~50 km from the northern coast. In both spring and autumn, lighter (i.e., slower flying) species and species with more rounded wings were concentrated nearest the coastline. Our results support the idea that morphology helps to shape broad-scale bird distributions along an ecological barrier and that migration exerts some selective force on passerine morphology. Furthermore, smaller species with less-efficient flight appear constrained to stopping over in close proximity to ecological barriers, illustrating the importance of coastal habitats for small passerine migrants.     

Optimal fat loads and long-distance flights by migrating Knots Calidris canutus, Sanderlings C. alba and Turnstones Arenaria interpres

Arctic waders often build up large fat loads and complete their migratory journeys by a few long-distance flights between traditional staging sites. Optimal fat loads and choices of staging sites differ depending on whether the birds are adapted to minimize energy or time spent on migration. In the latter case, we predict that the birds will depart for the next staging site when the instantaneous speed of migration expected after arrival at the next site, exceeds the corresponding speed at the departure site. The instantaneous migration speed is a function of the rate of fat deposition and the current fat load. As a consequence of this, overloading (birds deposit larger fat loads than needed merely for covering the flight distance to the next destination) and by-passing of possible, but low-quality staging sites, are expected under specific conditions in time-selected migration.
Estimates of fat deposition rates and departure fat loads were obtained by captures of Knots Calidris canutus , Sanderlings C. alba and Turnstones Arenaria interpres in W. Iceland during spring migration. Further fat deposition data referring to spring migration of these species were compiled from the literature. Fat deposition rates at different sites, as measured by the daily gain in mass relative to lean body-mass, range between 1.0 and 3.6%/day, and departure fuel loads (in % of lean body-mass) between 27 and 73%.
Comparison with flight range estimates suggests that overloading may be a regular phenomenon during spring migration of Knots, Sanderlings and Turnstones. Furthermore, fat deposition rates at different staging sites, and the general difference in migration patterns between spring and autumn, indicate that by-passing of possible staging sites may well occur. Hence, it cannot be excluded that the waders' migratory habits primarily serve to maximize the overall speed of migration.     

Short‐ and long‐term costs of reproduction in a migratory songbird

Costs of reproduction represent a common life‐history trade‐off. Critical to understanding these costs in migratory species is the ability to track individuals across successive stages of the annual cycle. We assessed the effects of total number of offspring fledged and date of breeding completion on pre‐migratory body condition, the schedule of moult and annual survival in a migratory songbird, the Savannah Sparrow Passerculus sandwichensis. Between 2008 and 2010, moult was delayed for individuals that finished breeding later in the breeding period and resulted in reduced lean tissue mass during the pre‐migratory period, suggesting an indirect trade‐off between the timing of breeding completion and condition just prior to migration. Lean tissue mass decreased as the number of offspring fledged increased in 2009, a particularly cool and wet year, illustrating a direct trade‐off between reproductive effort and condition just prior to migration in years when weather is poor. However, using a 17‐year dataset from the same population, we found that parents that fledged young late in the breeding period had the highest survival and that number of offspring fledged did not affect survival, suggesting that individuals do not experience long‐term trade‐offs between reproduction and survival. Taken together, our results suggest that adult Savannah Sparrows pay short‐term costs of reproduction, but that longer‐term costs are mitigated by individual quality, perhaps through individual variation in resource acquisition.     

Wing shape and migration in shorebirds: a comparative study

Migration is an energetically expensive and hazardous stage of the annual cycle of non‐resident avian species, and requires certain morphological adaptations. Wing shape is one of the morphological traits that is expected to be evolutionarily shaped by migration. Aerodynamic theory predicts that long‐distance migrants should have more pointed wings with distal primaries relatively longer than proximal primaries, an arrangement that minimizes induced drag and wing inertia, but this prediction has mostly been tested in passerine species. We applied the comparative method of phylogenetically independent contrasts to assess convergent evolution between wing shape and migration within shorebirds. We confirmed the assumption that long‐distance migrants have less rounded wings than species migrating shorter distances. Furthermore, wing roundedness negatively correlates with fat load and mean distance of migratory flights, the basic components of migration strategies. After controlling for interspecific differences in body size, we found no support for a link between wing length and migration, indicating that wing shape is a more important predictor of shorebird migratory behaviour than wing length. The results suggest that total migration distance and migratory strategy may simultaneously act on the evolution of wing shape in shorebirds, and possibly in other avian species.