Adverse wind conditions during northward Sahara crossings increase the in-flight mortality of Black-tailed Godwits

Long-distance migratory flights are predicted to be associated with higher mortality rates when individuals encounter adverse weather conditions. However, directly connecting environmental conditions experienced in-flight with the survival of migrants has proven difficult. We studied how the in-flight mortality of 53 satellite-tagged Black-tailed Godwits (Limosa limosa limosa) during 132 crossings of the Sahara Desert, a major geographical barrier along their migration route between The Netherlands and sub-Saharan Africa, is correlated with the experienced wind conditions and departure date during both southward and northward migration. We show that godwits experienced higher wind assistance during southward crossings, which seems to reflect local prevailing trade winds. Critically, we found that fatal northward crossings (15 deaths during 61 crossings) were associated with adverse wind conditions. Wind conditions during migration can thus directly influence vital rates. Changing wind conditions associated with global change may thus profoundly influence the costs of long-distance migration in the future

Variation From an Unknown Source: Large Inter-individual Differences in Migrating Black-Tailed Godwits

Variation in migratory behavior is the result of different individual strategies and fluctuations in individual performances. A first step toward understanding these differences in migratory behavior among individuals is, therefore, to assess the relative contributions of inter- and intra-individual differences to this variation. We did this using light-level geolocators deployed on the breeding grounds to follow continental black-tailed godwits (Limosa limosa limosa) throughout their south- and northward migrations over multiple years. Based on repeated tracks from 36 individuals, we found two general patterns in godwit migratory behavior: First, migratory timing in black-tailed godwits varies mostly because individual godwits migrate at different times of the year. Second, individuals also exhibit considerable variation in timing within their respective migratory windows. Although the absolute amount of inter-individual variation in timing decreased over the course of northward migration, individual godwits still arrived at their breeding grounds across a span of more than 5 weeks. These differences in migratory timing among individuals are larger than those currently observed in other migratory bird species and suggest that the selective forces that limit the variation in migratory timing in other species are relaxed or absent in godwits. Furthermore, we could not attribute these individual differences to the sex or wintering location of an individual. We suggest that different developmental trajectories enabled by developmental plasticity likely result in these generally consistent, life-long annual routines. To investigate this possibility and to gain an understanding of the different selection pressures that could be acting during migration and throughout a godwit's life, future studies should track juvenile godwits and other migratory birds from birth to adulthood while also manipulating their spatiotemporal environment during development

Migration route, stopping sites, and non-breeding destinations of adult Black-tailed Godwits breeding in southwest Fryslân, The Netherlands

In this paper, we extend our understanding of the migration of Black-tailed Godwits (Limosa limosa limosa) by describing: (1) the orientation and geographic locations of individual migratory routes and (2) the spatial distribution of godwits across seasons and years. We accomplish this using satellite-tracking data from 36 adult godwits breeding in the 200-ha Haanmeer polder in The Netherlands, from 2015 to 2018. During both southward and northward migration, godwits used a narrow migratory corridor along which most individuals made stops within a network of sites, especially the Bay of Biscay, France and Doñana, Spain. Most sites were used consistently by the same individuals across years. However, sites in Morocco were used during northward migration by 75% of individuals, but not revisited by the same individual across years. After southward migration, a small proportion (15%) of godwits spent the entire non-breeding period north of the Sahara, but most (85%) crossed the Sahara and spent at least part of the non-breeding season among seven coastal sites in West Africa and one site in the Inner Niger Delta. Although site-use patterns varied among individuals, individuals showed high site fidelity and were consistent in the number of sites they used from year to year. The considerable differences in the spatial distribution of individuals that breed within a kilometre of one another raise questions about the causes and consequences of individual migratory differences. We discuss that full annual cycle tracking of juveniles from birth to adulthood is needed to understand the source of these individual differences. Our results on the spatial distribution of godwits throughout their annual cycle lay an important foundation of information that can be used to help conserve this declining species

Age-dependent timing and routes demonstrate developmental plasticity in a long-distance migratory bird

Longitudinal tracking studies have revealed consistent differences in the migration patterns of individuals from the same populations. The sources or processes causing this individual variation are largely unresolved. As a result, it is mostly unknown how much, how fast and when animals can adjust their migrations to changing environments. We studied the ontogeny of migration in a long-distance migratory shorebird, the black-tailed godwit Limosa limosa limosa, a species known to exhibit marked individuality in the migratory routines of adults. By observing how and when these individual differences arise, we aimed to elucidate whether individual differences in migratory behaviour are inherited or emerge as a result of developmental plasticity. We simultaneously tracked juvenile and adult godwits from the same breeding area on their south- and northward migrations. To determine how and when individual differences begin to arise, we related juvenile migration routes, timing and mortality rates to hatch date and hatch year. Then, we compared adult and juvenile migration patterns to identify potential age-dependent differences. In juveniles, the timing of their first southward departure was related to hatch date. However, their subsequent migration routes, orientation, destination, migratory duration and likelihood of mortality were unrelated to the year or timing of migration, or their sex. Juveniles left the Netherlands after all tracked adults. They then flew non-stop to West Africa more often and incurred higher mortality rates than adults. Some juveniles also took routes and visited stopover sites far outside the well-documented adult migratory corridor. Such juveniles, however, were not more likely to die. We found that juveniles exhibited different migratory patterns than adults, but no evidence that these behaviours are under natural selection. We thus eliminate the possibility that the individual differences observed among adult godwits are present at hatch or during their first migration. This adds to the mounting evidence that animals possess the developmental plasticity to change their migration later in life in response to environmental conditions as those conditions are experienced

Variation in egg size of Black-tailed Godwits

As is the case for most avian species, there is considerable variation in the egg size of Continental Black-tailed Godwits Limosa l. limosa breeding in The Netherlands. It is interesting that egg size has costs and benefits yet varies considerably at the population level. To better understand this variation in egg size, we tested its relationship to a suite of individual and environmental factors. We found that egg size can decrease up to 2.8% throughout a breeding season and that egg size increases with clutch size by 1.4% with each additional egg in the clutch. Female body mass and body size explained 5% of the total variation in egg size observed across the population. Furthermore, females wintering south of the Sahara laid 3% smaller eggs than those wintering north of the Sahara. We also found that egg size increases with age, which may indicate age-related differences in the endogenous and/or exogenous conditions of females. The variation in egg size was, however, mostly the result of consistent differences among individuals across years (repeatability = 0.60). A comparison of daughters with mothers suggested that most of this individual repeatability reflects heritable variation (heritability = 0.64). The actual individual traits that underlie this heritable variation among individuals remain mostly undetermined. Smaller eggs did have a slightly lower chance of hatching, but we found no relationship between egg size and chick survival. Finally, nest and chick survival were strongly correlated with lay date. Thus, in Black-tailed Godwits, lay date may actually reflect a female's endogenous and/or exogenous condition at the moment of egg-laying. This finding may be general across birds, since food supplementation experiments usually result in advanced laying and larger clutch sizes rather than in larger eggs

High Migratory Survival and Highly Variable Migratory Behavior in Black-Tailed Godwits

Few studies have been able to directly measure the seasonal survival rates of migratory species or determine how variable the timing of migration is within individuals and across populations over multiple years. As such, it remains unclear how likely migration is to affect the population dynamics of migratory species and how capable migrants may be of responding to changing environmental conditions within their lifetimes. To address these questions, we used three types of tracking devices to track individual black-tailed godwits from the nominate subspecies (Limosa limosa limosa) throughout their annual cycles for up to 5 consecutive years. We found that godwits exhibit considerable inter- and intra-individual variation in their migratory behavior across years. We also found that godwits had generally high survival rates during migration, although survival was reduced during northward flights across the Sahara Desert. These patterns differ from those observed in most other migratory species, suggesting that migration may only be truly dangerous when crossing geographic barriers that lack emergency stopover sites and that the levels of phenotypic flexibility exhibited by some populations may enable them to rapidly respond to changing environmental conditions

A global threats overview for Numeniini populations: synthesising expert knowledge for a group of declining migratory birds

The Numeniini is a tribe of thirteen wader species (Scolopacidae, Charadriiformes) of which seven are near-threatened or globally threatened, including two critically endangered. To help inform conservation management and policy responses, we present the results of an expert assessment of the threats that members of this taxonomic group face across migratory flyways. Most threats are increasing in intensity, particularly in non-breeding areas, where habitat loss resulting from residential and commercial development, aquaculture, mining, transport, disturbance, problematic invasive species, pollution and climate change were regarded as having the greatest detrimental impact. Fewer threats (mining, disturbance, problematic native species and climate change) were identified as widely affecting breeding areas. Numeniini populations face the greatest number of non-breeding threats in the East Asian-Australasian Flyway, especially those associated with coastal reclamation; related threats were also identified across the Central and Atlantic Americas, and East Atlantic flyways. Threats on the breeding grounds were greatest in Central and Atlantic Americas, East Atlantic and West Asian flyways. Three priority actions were associated with monitoring and research: to monitor breeding population trends (which for species breeding in remote areas may best be achieved through surveys at key non-breeding sites), to deploy tracking technologies to identify migratory connectivity, and to monitor land-cover change across breeding and non-breeding areas. Two priority actions were focused on conservation and policy responses: to identify and effectively protect key non-breeding sites across all flyways (particularly in the East Asian - Australasian Flyway), and to implement successful conservation interventions at a sufficient scale across human-dominated landscapes for species’ recovery to be achieved. If implemented urgently, these measures in combination have the potential to alter the current population declines of many Numeniini species and provide a template for the conservation of other groups of threatened species

Dissecting the Shared Genetic Architecture of Suicide Attempt, Psychiatric Disorders, and Known Risk Factors

Background Suicide is a leading cause of death worldwide, and nonfatal suicide attempts, which occur far more frequently, are a major source of disability and social and economic burden. Both have substantial genetic etiology, which is partially shared and partially distinct from that of related psychiatric disorders. Methods We conducted a genome-wide association study (GWAS) of 29,782 suicide attempt (SA) cases and 519,961 controls in the International Suicide Genetics Consortium (ISGC). The GWAS of SA was conditioned on psychiatric disorders using GWAS summary statistics via multitrait-based conditional and joint analysis, to remove genetic effects on SA mediated by psychiatric disorders. We investigated the shared and divergent genetic architectures of SA, psychiatric disorders, and other known risk factors. Results Two loci reached genome-wide significance for SA: the major histocompatibility complex and an intergenic locus on chromosome 7, the latter of which remained associated with SA after conditioning on psychiatric disorders and replicated in an independent cohort from the Million Veteran Program. This locus has been implicated in risk-taking behavior, smoking, and insomnia. SA showed strong genetic correlation with psychiatric disorders, particularly major depression, and also with smoking, pain, risk-taking behavior, sleep disturbances, lower educational attainment, reproductive traits, lower socioeconomic status, and poorer general health. After conditioning on psychiatric disorders, the genetic correlations between SA and psychiatric disorders decreased, whereas those with nonpsychiatric traits remained largely unchanged. Conclusions Our results identify a risk locus that contributes more strongly to SA than other phenotypes and suggest a shared underlying biology between SA and known risk factors that is not mediated by psychiatric disorders.Peer reviewe

Unexpected diversity in socially synchronized rhythms of shorebirds

The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment1, 2, 3, 4. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions1, 5, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators6, 7, 8, 9, 10. Individuals can temporally segregate their daily activities (for example, prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (for example, group foraging, communal defence, pairs reproducing or caring for offspring)6, 7, 8, 9, 11. The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood5, 6, 7, 9. Here we investigate these rhythms in the context of biparental care, a particularly sensitive phase of social synchronization12 where pair members potentially compromise their individual rhythms. Using data from 729 nests of 91 populations of 32 biparentally incubating shorebird species, where parents synchronize to achieve continuous coverage of developing eggs, we report remarkable within- and between-species diversity in incubation rhythms. Between species, the median length of one parent’s incubation bout varied from 1–19 h, whereas period length—the time in which a parent’s probability to incubate cycles once between its highest and lowest value—varied from 6–43 h. The length of incubation bouts was unrelated to variables reflecting energetic demands, but species relying on crypsis (the ability to avoid detection by other animals) had longer incubation bouts than those that are readily visible or who actively protect their nest against predators. Rhythms entrainable to the 24-h light–dark cycle were less prevalent at high latitudes and absent in 18 species. Our results indicate that even under similar environmental conditions and despite 24-h environmental cues, social synchronization can generate far more diverse behavioural rhythms than expected from studies of individuals in captivity5, 6, 7, 9. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms