Annual Migration Research Articles

Seasonal migration and the evolution of an inverse latitudinal diversity gradient in shorebirds

AbstractAimWhile the evolution of seasonal migration and its association with biogeography have been the subject of numerous studies, its influence on species diversification has rarely been examined. The aim of this study is to explain the atypical latitudinal diversity gradient in shorebirds: did seasonal migration influence diversification and did the gradient evolve from higher in situ diversification or repeated transitions?LocationGlobal.Time PeriodPalaeogene to present.Major Taxa StudiedOrder Charadriiformes (shorebirds and allies). Shorebirds include the species with the longest annual migrations in birds and exhibit an inverse latitudinal diversity gradient, with more species breeding toward higher latitudes.MethodsWe first assessed the temporal and geographical framework of the evolution of migration using a newly reconstructed time‐calibrated phylogeny, and using the fossil record as a complementary source of information. We then used hidden state speciation and extinction models to test whether diversification and thus the latitudinal diversity gradient has been shaped by migratory behaviour or species latitudinal distribution.ResultsWe found that the ancestor of Charadriiformes was likely a tropical year‐round resident and that the current clade's distribution of diversity was not shaped by dispersal events out of the tropics but rather by higher in situ diversification in temperate biomes compared to tropical biomes. Seasonal migration did not affect diversification rate in our models. However, the evolution of seasonal migration seems to be a prerequisite to breed in temperate biomes, indirectly enabling the higher diversification observed in temperate biomes.Main ConclusionsOur results bring original insights into how the migratory behaviour acted as a precursor in the diversification and biogeographical history of a large bird clade, ultimately shaping an atypical latitudinal diversity gradient.

Impact of Venezuelan Migration on the Informal Workforce of Native Workers in Colombia

Colombia experienced a substantial increase in annual migration flow from Venezuela from 2013 to 2019, accumulating 1.7 million migrants by the end of 2019. According to migration data, 2016 was a breaking point in migration growth, with an increase of 137.57% compared with 2015 and at which time the influx of migrant workers began to be massive, rapid, and involuntary. In this regard, the research paper investigates, using a difference-in-differences model, the impacts on the labor market across different definitions of the informal workforce, testing the hypothesis that short-term labor migration increased (1) the number of employed individuals in companies with a workforce of fewer than five people, (2) the number of employed individuals not contributing to the social security system, and (3) the relative participation of the informal workforce in total employment from 2015 to 2018. The main results indicate an expansion in the labor market’s informal segment, increasing the number of non-returned native workers in the informal workforce without significant increases in the participation of informality in total employment. The results remain robust across various samples in models adjusted for departmental-, municipal-, and individual-level data. Following the economic theory, the research findings seem to follow a transmission mechanism in which migrant workers reduce labor costs and increase production in informal markets, providing better conditions to increase informal jobs for native workers. Several national and international stakeholders implementing income-generation alternatives in the border departments focusing on migrant employment services could find the research findings helpful in at least two aspects: (1) fighting cultural stereotypes upon which basis native workers tend to see migration as a threat to their current job holdings requires evidence that shows migrant workers contribute to economic growth and employment; (2) promoting better public policies to take advantage of initial conditions that favor labor integration of migrant workers such as cultural and language similarities among natives and migrants works better when there is evidence of the migration’s positive impacts.

Diverse migration patterns of anadromous white-spotted charr Salvelinus leucomaenis revealed from otolith microchemistry

Anadromous migration of salmonid fish has been extensively studied, primarily focusing on the dichotomous framework of anadromy and residency. However, there remains a limited understanding of intermediate migratory behaviors within the anadromous framework. Our study aimed to classify the lifetime migration patterns of the anadromous white-spotted charr Salvelinus leucomaenis within and among populations using otolith annuli and Sr:Ca ratios. Initially, the migratory histories of anadromous charr were divided into two stages: “virgin sea-run stage” and “veteran sea-run stage”. The former was further categorized into three types: ocean entry at age ≥1+ years old, early descending, and brackish use. The latter was grouped into four types: annual migrants, frequent migrants, retired migrants, and ocean residents. We found that the proportion of migration patterns varied among rivers, with multiple patterns coexisting within the same river. Migration patterns typically involving 1–5 years spent in freshwater rivers followed by annual oceanic migrations were the most abundant, although diverse patterns were also observed. In the virgin sea-run stage, some individuals experienced the ocean at age 0+ years or brackish environments before their first sea entry. In the veteran sea-run stage, we found individuals who had resided in either the ocean or rivers for over a year. Retired migrants, characterized by stopping oceanic migration at a certain age and subsequently spending time in rivers, were exclusive to southern rivers. Conversely, ocean residents who spend one or more years in the ocean were more frequent in northern regions. Consequently, the lifetime migration patterns of anadromous white-spotted charr may exhibit stronger ocean dependency at higher latitudes. The implications of this study highlight the complexity and flexibility of migratory behaviors within and among white-spotted charr populations.

Lunar synchrony, geography, and individual clocks shape autumn migration timing in an avian migrant.

Timing programs in animal migrants have been selected to synchronize movements that coincide with predictable resources on the breeding and nonbreeding grounds. Migrants face potential temporal conflicts if their migration schedules benefit from synchrony to conflicting rhythms associated with annual biogeographical (circannual) cues, lunar (circalunar) cues, or individually repeatable internal clocks. We repeat-tracked individuals of an avian lunaphilic species, Eastern Whip-poor-will (Antrostomus vociferus), for two to three successive autumn migrations to determine the influence of the lunar cycle, breeding location, and individual repeatability on migration timing. Almost all birds avoided departing for migration during a full moon, likely to take advantage of the bright moonlight to facilitate visual foraging and enhance pre-migration fattening. However, groups from two latitudinally distant sampling areas adjusted their autumn departure timing differently relative to the timing of the September full moon, presumably due to differences in seasonal prey availability. Individual repeatability increased throughout autumn migration, suggesting that the factors responsible for shaping migration timing may differ for different migration stages. Our results, that lunar synchrony, local climate, and individual internal clocks appeared to account for much of the variation in migration timing in whip-poor-wills, underscore the value of measuring potentially interacting factors that shape migratory behavior at species, group, and individual levels. It remains unclear if, or how, maintaining individually repeatable annual migration schedules provides an adaptive benefit for whip-poor-wills or other lunaphilic migrants. Further clarifying the reasons for phenotypic variation in whip-poor-will migration timing will improve predictions of their abilities to adjust migratory movements under changing environmental conditions.

Running the gauntlet; flyway-wide patterns of pollutant exposure in blood of migratory shorebirds

Shorebirds (order Charadriiformes) are among the world's most threatened avian taxa. Within the East Asian-Australasian Flyway (EAAF), a major threat to shorebirds' survival may be the gauntlet of pollution along the flyway. Metals, persistent organic pollutants (POPs), and per-/polyfluoroalkyl substances (PFASs) persist in the environment to the detriment of wildlife. In this study, we analysed element and PFAS concentrations in blood from 142 individuals across six species of Arctic-breeding migratory shorebirds with contrasting population trends, to discern species- and site-specific pollution differences, and determine how pollution correlated with population trends of EAAF shorebirds. Potential within-year pollution variations were investigated by blood-sampling birds at two sites, representing different points in the birds' annual migrations: staging in Taiwan on southward migrations and at non-breeding grounds in Western Australia (WA). Species' pollutant concentrations were compared to established population trends. Concentrations of potentially toxic elements were low in most individuals regardless of species. PFASs (range: <0.001–141 ng/g), Hg (<0.001–9910 ng/g) and Pb (<0.01–1210 ng/g) were higher in Taiwan than in WA (PFAS Taiwan median: 14.5 ng/g, WA median: 3.45 ng/g; Hg Taiwan: 338 ng/g, WA: 23.4 ng/g; Pb Taiwan: 36.8 ng/g, WA: 2.26 ng/g). Meanwhile As (range <0.001–8840 ng/g) and Se (290–47600 ng/g) were higher in WA than Taiwan (As Taiwan median: 500 ng/g, WA median: 1660 ng/g; Se Taiwan: 5490 ng/g, Se WA: 23700 ng/g). Nevertheless, pollutant concentrations in a subset of individuals may exceed sublethal effect thresholds (As, Se and PFASs). Finally, we found no consistent differences in pollution among species and demonstrated no correlation between pollution and population trends, suggesting pollution is likely not a major driver for population declines of EAAF shorebirds. However, ongoing and locally heavy environmental degradation and exposure to other contaminants not investigated here, such as POPs, warrants continued consideration when managing EAAF shorebird populations.

The role of tropical rainfall in driving range dynamics for a long-distance migratory bird.

Predicting how the range dynamics of migratory species will respond to climate change requires a mechanistic understanding of the factors that operate across the annual cycle to control the distribution and abundance of a species. Here, we use multiple lines of evidence to reveal that environmental conditions during the nonbreeding season influence range dynamics across the life cycle of a migratory songbird, the American redstart (Setophaga ruticilla). Using long-term data from the nonbreeding grounds and breeding origins estimated from stable hydrogen isotopes in tail feathers, we found that the relationship between annual survival and migration distance is mediated by precipitation, but only during dry years. A long-term drying trend throughout the Caribbean is associated with higher mortality for individuals from the northern portion of the species' breeding range, resulting in an approximate 500 km southward shift in breeding origins of this Jamaican population over the past 30 y. This shift in connectivity is mirrored by changes in the redstart's breeding distribution and abundance. These results demonstrate that the climatic effects on demographic processes originating during the tropical nonbreeding season are actively shaping range dynamics in a migratory bird.

Recent vs Historical Migrants: A Study on the Canadian Provincial Trade-Migration Nexus

Abstract We contribute to the literature by exploring the variation in the trade-creating effect of migration networks across historical migrants and recent migrants by applying a micro-founded gravity model of trade. Both the stock of historical migrants and recent migrants variables are constructed by merging Canadian Census data with the migration data available in Statistics Canada. We address the endogeneity issue by applying IV estimators including two-step feasible GMM and PPML with IV and fixed effects by utilizing the imputed annual migration flow, the historical stock, and recent stock of migrants as instrumental variables proposed by Peri and Requena (2010). Taking Canadian geographical features into account, this study also applies carefully measured gravity variables. We control for the time-varying, exporter-year fixed effects, and importer-year fixed effects in a panel estimation. Estimated results show that annual migration, recent provincial stock of migrants, and historical stock of migrants significantly increase Canadian interprovincial trade. This impact is stronger for the stock of historical migrants relative to the stock of recent migrants and annual migration flow. Sub-sample analysis shows that both recent and historical migration consistently increase interprovincial service trade, only but not interprovincial goods trade. A greater combination of English and French-speaking provinces-pair significantly increases interprovincial trade. Regional trade agreements significantly impact the interprovincial trade of Canada. Our estimated results are robust to different estimation methods and alternative measures for the migrants’ stock and flow variables.

Colony attendance and moult pattern of Cory's Shearwaters (Calonectris borealis) differing in breeding status and age

Migratory birds must fit three costly life‐history events within the annual cycle, reproduction, moult and migration, to minimize their overlap and maximize survival and breeding success. However, some seabirds, such as Cory's Shearwater Calonectris borealis, overlap body moult and breeding, with flight feather renewal occurring in late chick‐rearing. In contrast, the moult patterns of non‐breeding adult (sabbatical) and immature Cory's Shearwaters, which also attend the colony during the breeding season, remain poorly understood. Furthermore, the potential implications of life‐stage and breeding status trade‐offs on moult status and colony attendance in non‐breeders has rarely been investigated. Surveying different areas within one colony between June and September 2013 and 2014, we studied the age and breeding status composition of birds attending the breeding colony and scored moult of their body (breast and upper‐neck), wing and tail feathers. We found that in addition to breeders (n = 165), 57.6% of the birds (n = 389) attending the colony were 4‐ to 10‐year‐old immatures (n = 132) and adult sabbatical shearwaters (n = 92). Sabbaticals and 8‐ to 10‐year‐old immatures (n = 28) were present at the colony during incubation, whereas only three sabbatical birds and no 8‐ to 10‐year‐old immatures were captured in late chick‐rearing. Conversely, 4‐ to 7‐year‐old immatures arrived later in the season but were still present in late chick‐rearing. Sabbatical and 8‐ to 10‐year‐old immatures were moulting body feathers at the same time as adult breeders, whereas, among 4‐ to 7‐year‐old immatures, older birds moulted earlier than younger birds. A larger proportion of sabbatical birds were replacing tail feathers compared with adult breeders. However, there was no evidence that sabbaticals or 8‐ to 10‐year‐old immatures differed in wing moult from adult breeders until August. Overall, our study shows that colony attendance by non‐breeding adults and immatures is widespread in this population. The synchronous moult schedule of flight and body feathers across age groups at different life‐history stages may suggest that this aspect of moult is controlled by environmental conditions.

Using genetic comparisons of populations from Arizona, Mexico, and Texas to investigate fall armyworm migration in the American southwest.

Fall armyworm (FAW) is a global agricultural pest, causing substantial economic losses in corn and many other crops. Complicating efforts to control this pest is its capacity for long distance flights, which has been described in greatest detail for the central and eastern sections of the United States. FAW infestations are also routinely found in agricultural areas in southern Arizona, which lie beyond the western limits of the mapped migratory pathways. Climate suitability analysis found that the affected Arizona locations cannot support permanent FAW populations, indicating that these FAW most likely arise from annual migrations. A better understanding of this migration would provide insights into how large moth populations can move across desert habitats as well as the degree of gene flow occurring between FAW populations across the North American continent. In this study the Arizona populations were genetically characterized and compared to a selection of permanent and migratory FAW from multiple sites in the United States and Mexico. The results are consistent with migratory contributions from permanent populations in the states of Texas (United States) and Sinaloa (Mexico), while also providing evidence of significant barriers to gene flow between populations within Mexico. An unexpected finding was that two genetically distinct FAW subpopulations known as "host strains" have a differential distribution in the southwest that may indicate significant differences in their migration behavior in this region. These findings indicate that the combination of mitochondrial and Z-linked markers have advantages in comparing FAW populations that can complement and extend the findings from other methods.

Got milkweed? Genetic assimilation as potential source for the evolution of nonmigratory monarch butterfly wing shape.

Monarch butterflies (Danaus plexippus) are well studied for their annual long-distance migration from as far north as Canada to their overwintering grounds in Central Mexico. At the end of the cold season, monarchs start to repopulate North America through short-distance migration over the course of multiple generations. Interestingly, some populations in various tropical and subtropical islands do not migrate and exhibit heritable differences in wing shape and size, most likely an adaptation to island life. Less is known about forewing differences between long- and short-distance migrants in relation to island populations. Given their different migratory behaviors, we hypothesized that these differences would be reflected in wing morphology. To test this, we analyzed forewing shape and size of three different groups: nonmigratory, lesser migratory (migrate short-distances), and migratory (migrate long-distances) individuals. Significant differences in shape appear in all groups using geometric morphometrics. As variation found between migratory and lesser migrants has been shown to be caused by phenotypic plasticity, and lesser migrants develop intermediate forewing shapes between migratory and nonmigratory individuals, we suggest that genetic assimilation might be an important mechanism to explain the heritable variation found between migratory and nonmigratory populations. Additionally, our research confirms previous studies which show that forewing size is significantly smaller in nonmigratory populations when compared to both migratory phenotypes. Finally, we found sexual dimorphism in forewing shape in all three groups, but for size in nonmigratory populations only. This might have been caused by reduced constraints on forewing size in nonmigratory populations.

A Bayesian approach to estimate annual bilateral migration flows for South America using census data

Abstract Censuses are an important source of international migration flow data. However, their use is limited since they indirectly reflect migration, capturing migrant transitions over long intervals rather than migration events, whilst also underestimating the number of infants and deaths. Censuses also neglect migration of those who are native-born when they only include questions on country of birth, and have sparse temporal availability. We propose a Bayesian hierarchical model to overcome these limitations and produce a set of robust annual migration flow estimates for South American countries. Our model translates five-year transition data from censuses into annual series, corrects biases that arise due to differences in measurement and census data quality across countries, and is grounded in migration theory to impute missing migration data between censuses.

Revelations of interannual dune evolution from the swiftest aeolian system on Mars by MRO/HiRISE long-term monitoring

The north polar region of Mars, with its greater atmospheric pressure and vast inventory of ever-changing volatiles (e.g., CO2, H2O), hosts arguably the most active and diverse aeolian bedform systems on the planet. Here, we explore how these dune fields evolve spatiotemporally using up to 8 Mars years (16 Earth years) of MRO HiRISE observations to test the impact of various boundary conditions on annual mobility. A high degree of sand flux heterogeneity was observed for some dunes, whereas other sites displayed steady-state migration relative to long-term rates. These large changes in annual migration are attributed to the variable length of the frost-free seasons, sediment availability in relation to the timing of peak katabatic winds, and the influence of global dust storms on seasonal ice thickness. Consistent with our previous work, we continue to observe extremely high transport rates at Olympia Cavi. All stages of aeolian system evolution are observable (sand patch > protodune > dune), along with additional phenomena not previously observed outside of terrestrial settings (e.g., dune calving and collisions, remote transfer). Transitory protodunes may evolve from modest sand mounds to prominent barchans with slipfaces several meters tall within 3–5 Mars years, while adjacent duneforms may suffer slipfaces collapse as they lose sand supply. These Martian protodunes, which appear to be larger than terrestrial equivalents, and mature dunes found downwind are among the swiftest yet reported on Mars. These rapidly evolving cryo-aeolian systems provide a window into longer-term landscape evolution of non-polar dune fields.

The role of Council of Europe law and ECtHR practice in the protection of refugee rights

h negotiations and litigation, and the principle of peaceful settlement of disputes is one of the fundamental principles of international law, there are still subjects of international law in the world who prefer the military way of dispute settlement and violate the fundamental principles of peaceful interstate relations. One of the most striking examples is the armed aggression of the Russian Federation against an independent European state - Ukraine. Russia not only violated the fundamental principles of international law, such as peaceful settlement of disputes, respect for the sovereignty of the state, etc. but also caused a huge number of human rights violations. As a result of the armed aggression, many Ukrainian citizens were forced to seek refuge abroad in European countries. Thus, the issue of legal regulation of the rights of refugees in Europe is relevant both for the European countries that accept and protect such refugees, and for the citizens of Ukraine who are forced to obtain such status. The author of the article paid special attention to the protection of refugees' rights within the framework of the Council of Europe law and the ECtHR case law, as these institutions are key to the protection of human rights in the European space. Thus, the study of the role of the Council of Europe and the ECtHR will provide an opportunity to understand the overall picture of refugee protection in the region. In general, the growth of annual migration volumes makes it necessary to pay special attention to this issue, especially in relation to forced migrants who are vulnerable and in need of protection by the host state. The purpose of this article is to explore the role and significance of the law of the Council of Europe, as well as the ECHR in the protection of the rights and freedoms of refugees in the European region, as well as the current issues faced by Ukrainian refugees in European countries. In addition, the article examines the fundamental approaches to the understanding of the concept of refugee in the theoretical and legal plane.

Regional oceanography affects humpback whale entanglements in set fishing gear

AbstractHumpback whales Megaptera novaengliae undertake annual migrations along eastern Australia, where they can be susceptible to entanglement in set fishing gear. This can potentially result in both sublethal and fatal outcomes for the whales, and financial losses for the fishing industry, including loss of gear and catch. Interannual fluctuations in entanglement records suggest that dynamic oceanographic features may be associated with the whales' migration path, and therefore, risk of entanglement. Using records of demersal fish traps off the coast of New South Wales (NSW), we identify two areas of high fishing pressure and entanglement risk overlap. Within each area, we combine entanglement observations with metrics associated with the East Australian Current (EAC) and climate (i.e., southern oscillation index). We show that the strength and position of the EAC was associated with the likelihood of entanglement in set fishing gear. In northern NSW (30.3° S), entanglement risk was highest between July and October when the EAC is relatively close to the coast. In contrast, there was no evidence suggesting that oceanography further south in the separation zone of the EAC (33.8° S) was associated with risk of entanglement. In the years following a strongly negative SOI (i.e., El Niño events), entanglement risk was also reduced. While we provide clear linkages with regional oceanographic dynamics and entanglement risk off NSW, if a dynamic ocean management approach to reducing entanglements is to be realized, further research into the fine‐scale movements of humpback whales is needed.

Icelandic Whimbrel first migration: Non‐stop until West Africa, yet later departure and slower travel than adults

Migratory behaviour in young individuals is probably developed by using a complex suite of resources, from molecular information to social learning. Comparing the migration of adults and juveniles provides insights into the possible contribution of those developmental factors to the ontogeny of migration. We show that, like adults, juvenile Icelandic Whimbrel Numenius phaeopus islandicus fly non‐stop to West Africa, but on average depart later, follow less straight paths and stop more after reaching land, resulting in slower travel speeds. We argue how the variation in departure dates, the geographical location of Iceland and the annual migration routine of this population make it a good model to study the ontogeny of migration.

Examining environmental conditions that influence long-term Antarctic blue whale migration patterns in the Southern Hemisphere using an 18-year passive acoustic dataset

Antarctic blue whales (Balaenoptera musculus intermedia) are difficult to study due to the low numbers and cryptic behaviour. The largest subspecies of blue whale migrates from Antarctic feeding areas to temperate and tropical breeding grounds every year. Their use of these remote areas makes it difficult to detect them using visual survey methods. However, blue whales are vocal animals and sing throughout the year especially during their annual migration. By using passive acoustic monitoring, we can study the long-term migration patterns of Antarctic blue whales across the Southern Hemisphere. Using an 18-year passive acoustic dataset from the CTBTO, we examined the migration patterns of Antarctic blue whales across four different locations spread across all three major ocean basins. We modelled blue whale acoustic detections with environmental variables including El Niño Southern Oscillation, the Southern Annular Mode, and yearly Antarctic sea-ice extent. We also examined krill abundance estimates from Krill Base in our models. We found that the whale call detections at the four sites were correlated with different variables. The variables were also correlated with various degrees of lag. Our study provides evidence that these whales vary their migration patterns from year-to-year with respect to changing oceanic, and climatic conditions.

A trans-Pacific movement reveals regular migrations of humpback whales Megaptera novaeangliae between Russia and Mexico

Humpback whalesMegaptera novaeangliaeundertake extensive annual migrations, have complex migratory patterns, and have held several mammalian long-distance movement records. Here, we report on a whale known to feed in the Russian Far East that was sighted in breeding areas on either side of the North Pacific, the Mariana Islands and Mexico, in less than 1 yr (357 d apart). This is the longest published distance (11261 km great-circle route) between 2 unique sightings of a photo-identified humpback whale to date. To understand the context of this movement, we investigated records of whales that had been sighted in Russian feeding areas and Mexican breeding areas using historic and newly available photo-identification data. We found 117 humpback whales documented in both countries between 1998 and 2021, revealing a substantial increase from the only 11 matches that were previously known. These whales exhibited high site fidelity to Mexico, with one-third seen in multiple years, and up to 10 yr. However, we also found that they changed breeding areas more frequently than Mexico whales matched to other feeding areas, illustrating how the Mariana Islands-Mexico movement may have occurred. We document the first complete round-trip migrations between Mexico and Russia, a journey of &gt;16400 km, the longest known migration of Northern Hemisphere humpback whales. Our data demonstrate regular trans-Pacific movements of humpback whales in the North Pacific, highlighting the importance of Mexico for the species ocean-basin-wide and the need for effective local management to aid in the conservation of multiple at-risk distinct population segments.

Camera-based automated monitoring of flying insects in the wild (Camfi). II. flight behaviour and long-term population monitoring of migratory Bogong moths in Alpine Australia.

The Bogong moth Agrotis infusa is well known for its remarkable annual round-trip migration from its breeding grounds across eastern and southern Australia to its aestivation sites in the Australian Alps, to which it provides an important annual influx of nutrients. Over recent years, we have benefited from a growing understanding of the navigational abilities of the Bogong moth. Meanwhile, the population of Bogong moths has been shrinking. Recently, the ecologically and culturally important Bogong moth was listed as endangered by the IUCN Red List, and the establishment of a program for long-term monitoring of its population has been identified as critical for its conservation. Here, we present the results of two years of monitoring of the Bogong moth population in the Australian Alps using recently developed methods for automated wildlife-camera monitoring of flying insects, named Camfi. While in the Alps, some moths emerge from the caves in the evening to undertake seemingly random flights, filling the air with densities in the dozens per cubic metre. The purpose of these flights is unknown, but they may serve an important role in Bogong moth navigation. We found that these evening flights occur throughout summer and are modulated by daily weather factors. We present a simple heuristic model of the arrival to and departure from aestivation sites by Bogong moths, and confirm results obtained from fox-scat surveys which found that aestivating Bogong moths occupy higher elevations as the summer progresses. Moreover, by placing cameras along two elevational transects below the summit of Mt. Kosciuszko, we found that evening flights were not random, but were systematically oriented in directions relative to the azimuth of the summit of the mountain. Finally, we present the first recorded observations of the impact of bushfire smoke on aestivating Bogong moths - a dramatic reduction in the size of a cluster of aestivating Bogong moths during the fire, and evidence of a large departure from the fire-affected area the day after the fire. Our results highlight the challenges of monitoring Bogong moths in the wild and support the continued use of automated camera-based methods for that purpose.

World’s human migration patterns in 2000–2019 unveiled by high-resolution data

Despite being a topical issue in public debate and on the political agenda for many countries, a global-scale, high-resolution quantification of migration and its major drivers for the recent decades remained missing. We created a global dataset of annual net migration between 2000 and 2019 (~10 km grid, covering the areas of 216 countries or sovereign states), based on reported and downscaled subnational birth (2,555 administrative units) and death (2,067 administrative units) rates. We show that, globally, around 50% of the world’s urban population lived in areas where migration accelerated urban population growth, while a third of the global population lived in provinces where rural areas experienced positive net migration. Finally, we show that, globally, socioeconomic factors are more strongly associated with migration patterns than climatic factors. While our method is dependent on census data, incurring notable uncertainties in regions where census data coverage or quality is low, we were able to capture migration patterns not only between but also within countries, as well as by socioeconomic and geophysical zonings. Our results highlight the importance of subnational analysis of migration—a necessity for policy design, international cooperation and shared responsibility for managing internal and international migration.

Heat band, rain band and heat low migration: process-based evaluation of some CMIP6 GCMs over West Africa

Climate model evaluation presents a crucial pathway into the investigation of the simulation of future climate. It presents the only lens through which the future states of the climate of the planet can be explored. In this study, reference datasets including reanalysis products have been used to demonstrate the climatological annual migration of the West African Monsoon System (WAMS) in three components, namely, the West African Heat Low (WAHL), the West African Heat Band (WAHB) and the West African Rain Band (WARB). We have used 8 Global Climate Models (GCMs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to assess how the models represent the climatological annual migration of these three features over the same domain for the same period. The results show close linkages between the WAHL, WAHB and the WARB as signature components of the WAMS in their climatological annual dynamics. All three features migrate from the south (with the minimum intensities) in January to the north (with the maximum intensities) in August over the region. The GCMs represent the climatological annual dynamics of all three features to some extent. However, in most of the models analysed the WAHL is too weak, and the WAHB and WARB are located too far south. Insights from this study can be beneficial for investigations of the future state of the WAMS. Also, development of models for the region should target the improved simulation of these features, specifically the intensity of the WAHL, and the locations of the WAHB and WARB.