Flying, fasting, and feeding in birds during migration: a nutritional and physiological ecology perspective

Unlike exercising mammals, migratory birds fuel very high intensity exercise (e.g., flight) with fatty acids delivered from the adipose tissue to the working muscles by the circulatory system. Given the primary importance of fatty acids for fueling intense exercise, we discuss the likely limiting steps in lipid transport and oxidation for exercising birds and the ecological factors that affect the quality and quantity of fat stored in wild birds. Most stored lipids in migratory birds are comprised of three fatty acids (16:0, 18:1 and 18:2) even though migratory birds have diverse food habits. Diet selection and selective metabolism of lipids play important roles in determining the fatty acid composition of birds which, in turn, affects energetic performance during intense exercise. As such, migratory birds offer an intriguing model for studying the implications of lipid metabolism and obesity on exercise performance. We conclude with a discussion of the energetic costs of migratory flight and stopover in birds, and its implications for bird migration strategies.

Fuelling rates of garganey (Anas querquedula) staging in the Camargue, Southern France, during spring migration

Most species of long-distance migratory birds put on energy stores to fuel their travels. However, recent studies have highlighted the potential costs associated with carrying too much fuel, either through increased predation risk or decreased flight efficiency. Consequently, it is now widely accepted that migratory birds should carry optimal rather than maximum fuel loads. Information from 372 garganey (Anas querquedula) ringed and recaptured at least once during the same spring in the Camargue, southern France, was used to document fuelling rates of individual ducks in relation to environmental variation and individual variation in condition. On average, garganey added very little fuel stores in the Camargue (mean gain per day = 0.33 g, less than 0.5% of mean body-mass in total over an average stay of 5 days). Fuelling rates were negatively correlated with body mass at capture, but it cannot be excluded that this pattern was a statistical artefact. Given their body-mass at ringing, garganey could potentially still fly long distances when they stop in the Camargue. It is therefore likely that the aim of their stay in southern France is more for resting than refuelling, a finding that may have implications for the proper management of stop-over sites.

Fuel stores of juvenile waders on autumn migration in high arctic Canada

Little is known about the fuel stores that arctic-breeding waders put on before departure from the breeding grounds. During a ship-based expedition to arctic Canada, we caught waders at seven, mainly coastal sites, with-in 68°-76°N and 139°-67°W, from 28 July to 31 August 1999. More than two hundred waders of twelve species were trapped, mainly White-rumped Calidris fuscicollis, Semipalmated C. pusilla, Baird's C. bairdii and Buff-breasted Sandpipers Tryngites subruficollis. The vast majority of the birds were juveniles. Body masses and visual fat stores were low, close to the lowest values found anywhere during the non-breeding season for the different species. The relatively fattest birds were Buff-breasted Sandpipers, but they were still far from their maximum body mass on spring migration. We conclude that juvenile arctic waders depart from their natal areas with only small fuel stores, which is in concordance with a time-minimising migration strategy.

Predicting migratory flight altitudes by physiological migration models

Using the altitudinal profiles of wind, temperature, pressure, and humidity in three flight models, we tried to explain the altitudinal distributions of nocturnal migrants recorded by radar above a desert in southern Israel. In the simplest model, only the tailwind component was used as a predictor of the most preferred flight altitude (T model). The energy model (E model) predicted flight ranges according to mechanical power consumption in flapping flight depending on air density and wind conditions, assuming optimal adjustment of airspeed and compensation of crosswinds, and including the influence of mass loss during flight. The energy-water model (EW model) used the same assumptions and parameters as the E model but also included restrictions caused by dehydration. Because wind was by far the most important factor governing altitudinal distribution of nocturnal migrants, differences in predictions of the three models were small. In a first approach, the EW model performed slightly better than the E model, and both performed slightly better than the T model. Differences were most pronounced in spring, when migrants should fly high according to wind conditions, but when climbing and descending they must cross lower altitudes where conditions are better with respect to dehydration. A simplified energy model (Es model) that omits the effect of air density on flight costs explained the same amount of variance in flight altitude as the more complicated E and EW models. By omitting the effect of air density, the Es model predicted lower flight altitudes and thus compensated for factors that generally bias height distributions downward but are not considered in the models (i.e. climb and descent through lower air layers, cost of ascent, and decrease of oxygen partial pressure with altitude). Our results confirm that wind profiles, and thus energy rather than water limitations, govern the altitudinal distribution of nocturnal migrants, even under the extreme humidity and temperature conditions in the trade wind zone.

Metabolic constraints on long-distance migration in birds

The flight range of migrating birds depends crucially on the amount of fuel stored by the bird prior to migration or taken up en route at stop-over sites. However, an increase in body mass is associated with an increase in energetic costs, counteracting the benefit of fuel stores. Water imbalance, occurring when water loss exceeds metabolic water production, may constitute another less well recognised problem limiting flight range. The main route of water loss during flight is via the lungs; the rate of loss depends on ambient temperature, relative humidity and ventilatory flow and increases with altitude. Metabolite production results in an increased plasma osmolality, also endangering the proper functioning of the organism during flight. Energetic constraints and water-balance problems may interact in determining several aspects of flight behaviour, such as altitude of flight, mode of flight, lap distance and stop-over duration. To circumvent energetic and water-balance problems, a bird could migrate in short hops instead of long leaps if crossing of large ecological barriers can be avoided. However, although necessitating larger fuel stores and being more expensive, migration by long leaps may sometimes be faster than by short hops. Time constraints are also an important factor in explaining why soaring, which conserves energy and water, occurs exclusively in very large species: small birds can soar at low speeds only. Good navigational skills involving accurate orientation and assessment of altitude and air and ground speed assist in avoiding physiological stress during migration.

Migration, acculturation and environment: determinants of obesity among Iranian migrants in Australia

While migration from low- to high-income countries is typically associated with weight gain, the obesity risks of migration from middle-income countries are less certain. In addition to changes in behaviours and cultural orientation upon migration, analyses of changes in environments are needed to explain post-migration risks for obesity. The present study examines the interaction between obesity-related environmental factors and the pattern of migrant acculturation in a sample of 152 Iranian immigrants in Victoria, Australia. Weight measurements, demographics, physical activity levels and diet habits were also surveyed. The pattern of acculturation (relative integration, assimilation, separation or marginalization) was not related to body mass index, diet, or physical activity behaviours. Three relevant aspects of participants' perception of the Australian environment (physically active environments, social pressure to be fit, unhealthy food environments) varied considerably by demographic characteristics, but only one (physically active environments) was related to a pattern of acculturation (assimilation). Overall, this research highlighted a number of key relationships between acculturation and obesity-related environments and behaviours for our study sample. Theoretical models on migration, culture and obesity need to include environmental factors.

Migration and the right to social security: perceptions of off-farm migrants' rights to social insurance in China's Jiangsu Province

In 2001 China ratified the International Covenant on Economic, Social and Cultural Rights. By so doing the national government became legally bound, "to the maximum of its available resources", to achieve "progressively" full realization of the rights specified in the Covenant. Included amongst these entitlements is the "right of everyone to social security, including social insurance". This paper uses data from Jiangsu to examine the extent to which urbanites agree that previously disenfranchised migrants have the same right to social insurance as the urban population. Many urbanites fear that their existing entitlements to social protection will be diluted if social insurance coverage is extended to include new populations. Accordingly, state agencies and the media have sought to promote acceptance of a more positive view of migrant workers than has traditionally prevailed within towns and cities. We find that younger urban residents, urban residents who already have social insurance and urban residents working in the state-owned sector are more likely to agree that migrants have the same right to social insurance as the urban population. © 2007 Institute of World Economics and Politics, Chinese Academy of Social Sciences.

Effects of emergence time and early social rearing environment on behaviour of Atlantic salmon: consequences for juvenile fitness and smolt migration

Consistent individual differences in behaviour have been well documented in a variety of animal taxa, but surprisingly little is known about the fitness and life-history consequences of such individual variation. In wild salmonids, the timing of fry emergence from gravel spawning nests has been suggested to be coupled with individual behavioural traits. Here, we further investigate the link between timing of spawning nest emergence and behaviour of Atlantic salmon (Salmo salar), test effects of social rearing environment on behavioural traits in fish with different emergence times, and assess whether behavioural traits measured in the laboratory predict growth, survival, and migration status in the wild. Atlantic salmon fry were sorted with respect to emergence time from artificial spawning nest into three groups: early, intermediate, and late. These emergence groups were hatchery-reared separately or in co-culture for four months to test effects of social rearing environment on behavioural traits. Twenty fish from each of the six treatment groups were then subjected to three individual-based behavioural tests: basal locomotor activity, boldness, and escape response. Following behavioural characterization, the fish were released into a near-natural experimental stream. Results showed differences in escape behaviour between emergence groups in a net restraining test, but the social rearing environment did not affect individual behavioural expression. Emergence time and social environment had no significant effects on survival, growth, and migration status in the stream, although migration propensity was 1.4 to 1.9 times higher for early emerging individuals that were reared separately. In addition, despite individuals showing considerable variation in behaviour across treatment groups, this was not translated into differences in growth, survival, and migration status. Hence, our study adds to the view that fitness (i.e., growth and survival) and life-history predictions from laboratory measures of behaviour should be made with caution and ideally tested in nature.

A shadow-like task migration model based on context semantics for mobile and pervasive environments

Pervasive computing is a user-centric mobile computing paradigm, in which tasks should be migrated over different platforms in a shadow-like way when users move around. In this paper, we propose a context-sensitive task migration model that recovers program states and rebinds resources for task migrations based on context semantics through inserting resource description and state description sections in source programs. Based on our model, we design and develop a task migration framework xMozart which extends the Mozart platform in terms of context awareness. Our approach can recover task states and rebind resources in the context-aware way, as well as support multi- modality I/O interactions. The extensive experiments demonstrate that our approach can migrate tasks by resuming them from the last broken points like shadows moving along with the users.

Migration and refugee law: principles and practice in Australia

Migration and refugee law and policy is fundamentally concerned with the choices that we as a nation make regarding the people that we allow into our community and to share our resources. Migration and Refugee Law: Principles and Practice in Australia 2nd Edition provides an overview of the legal principles governing the entry of people into Australia. The 2nd edition encompasses legislative amendments and significant judicial decisions to 2007. As well as dealing with migration and refugee law today, the book analyses the policy and moral considerations underpinning this area of law. This is especially so in relation to refugee law, which is one of the most divisive social issues of our time. The book suggests proposals for change and how this area of law can be made more coherent and principled. This book is written for all people who have an interest in migration and refugee law.

Environmental migration and capital mobility

Based on utility equalization, this paper considers a developing economy with labor migration. Pollution and capital taxes are imposed on producers in the polluted sector. The optimal policy combinations of capital taxes and pollution taxes for the host economy are examined. A zero capital tax is required for increasing mobility of capital to raise real GDP, while a larger than Pigovian pollution tax is needed for enhancing environmental amenities. The impacts on those two optimal tax rates are examined theoretically and numerically if foreign countries adopt higher environmental standards or if foreign countries impose tax credits on foreign investments.

Addressing migration-related social and health inequalities in Australia: call for research funding priorities to recognise the needs of migrant populations

Objective Migrants constitute 26% of the total Australian population and, although disproportionately affected by chronic diseases, they are under-represented in health research. The aim of the present study was to describe trends in Australian Research Council (ARC)- and National Health and Medical Research Council (NHMRC)-funded initiatives from 2002 to 2011 with a key focus on migration-related research funding.Methods Data on all NHMRC- and ARC-funded initiatives between 2002 and 2011 were collected from the research funding statistics and national competitive grants program data systems, respectively. The research funding expenditures within these two schemes were categorised into two major groups: (1) people focused (migrant-related and mainstream-related); and (2) basic science focused. Descriptive statistics were used to summarise the data and report the trends in NHMRC and ARC funding over the 10-year period.Results Over 10 years, the ARC funded 15 354 initiatives worth A$5.5 billion, with 897 (5.8%) people-focused projects funded, worth A$254.4 million. Migrant-related research constituted 7.8% of all people-focused research. The NHMRC funded 12 399 initiatives worth A$5.6 billion, with 447 (3.6%) people-focused projects funded, worth A$207.2 million. Migrant-related research accounted for 6.2% of all people-focused initiatives.Conclusions Although migrant groups are disproportionately affected by social and health inequalities, the findings of the present study show that migrant-related research is inadequately funded compared with mainstream-related research. Unless equitable research funding is achieved, it will be impossible to build a strong evidence base for planning effective measures to reduce these inequalities among migrants.What is known about the topic? Immigration is on the rise in most developing countries, including Australia, and most migrants come from low- and middle-income countries. In Australia, migrants constitute 26% of the total Australian population and include refugee and asylum seeker population groups. Migrants are disproportionately affected by disease, yet they have been found to be under-represented in health research and public health interventions.What does this paper add? This paper highlights the disproportions in research funding for research among migrants. Despite migrants being disproportionately affected by disease burden, research into their health conditions and risk factors is grossly underfunded compared with the mainstream population.What are the implications for practitioners? Migrants represent a significant proportion of the Australian population and hence are capable of incurring high costs to the Australian health system. There are two major implications for practitioners. First, the migrant population is constantly growing, therefore integrating the needs of migrants into the development of health policy is important in ensuring equity across health service delivery and utilisation in Australia. Second, the health needs of migrants will only be uncovered when a clear picture of their true health status and other determinants of health, such as psychological, economic, social and cultural, are identified through empirical research studies. Unless equitable research funding is achieved, it will be impossible to build a strong evidence base for planning effective measures to reduce health and social inequalities among migrant communities.

Possible Migration Routes Through Maine by Vernal Migrants

In this study we evaluate the possibility of two routes of migration into the state of Maine. The first possible route would be for migrants to continue along the coast, north of the Maine/New Hampshire border, and later swinging inland across the interior. The second path is for migrants who come up the east coast and straight into Maine, spreading across the state as they move north. In order to evaluate these possible routes we utilize a citizen-science project that measures the spring arrival dates of migrants according to the biophysical regions of Maine (Wilson 2007). Independent t-Tests and maps indicate that there is a trend of birds continuing along the coast before moving inland; six of the nine species show this pattern. Of the nine birds studied, only the eastern phoebe showed a significant trend of moving directly inland and moving across the state. Two birds show non-significant patterns of migration which could indicate insufficient data, or random migration patterns. The results are not conclusive because several of the biophysical regions have less reporting, and so the relationships among regions regarding arrival dates are skewed. Continued data collection and analysis is recommended.