Migration Strategies Research Articles

Divergent ornamentation within a single population of the barn swallow.

Differential migration strategies favour different sets of characteristics, including sexually selected ornamentation. Such phenotypic variation is particularly evident in a population with partial migration, where migrants and non-migrants co-exist. Partial migration provides insights into the link between migration, local environment and ornamentation, although empirical studies remain scarce. Here, we studied the plumage traits of barn swallows (Hirundo rustica) in southern Japan, where both winterings and migrants breed sympatrically. We further examined this relationship with multiple isotopes (δ2H, δ13C, δ15N and δ34S), which provides insight into their moulting habitat. Among males, winterings and migrants differed in their morphological traits: wintering males had shorter wings, which suggests the high demand for flight apparatus in migratory birds. Moreover, wintering males had larger white tail spots and less colourful throat patches than migratory males, indicating ornament divergence between them. Wintering males had a significantly smaller isotopic space when examining the combinations of δ34S with the other isotopes compared to migratory males, which indicates a differential geographic range between them, perhaps because of the limited variation in the distance to the sea in wintering males. As in males, wintering females had a significantly smaller isotopic space than migrant females, but there were few morphological differences between migratory and wintering females. Instead, some morphological traits were related to isotope values in females. These results indicate sex-specific linkage between migration, local environment, and ornamentation.

Phenotypic Plasticity in Locusts: Trade-Off Between Migration and Reproduction.

Locusts exhibit phenotypic plasticity in response to population density changes, with distinct phenotypes in the solitary and gregarious phases. In the past decade, many studies have revealed the molecular mechanisms underlying phase changes, which include the change of body coloration, pheromones, behavior, flight, fecundity, immunity, and aging. Our understanding of the molecular mechanisms related to these phenotypic differences has expanded in breadth and depth with the decoding of the locust genome, involving transcriptional, post-transcriptional, translational, and epigenetic regulation. Large-scale regulation networks composed of genes and noncoding RNAs reflect the systematic modifications of the locust phase transition in response to environmental changes. Gene manipulation techniques have verified the functions of specific genes and related pathways in phase changes. This review highlights the latest advances in studies of locust phase changes and suggests that the divergence of energy and metabolism allocation in gregarious and solitary locusts is an adaptive strategy for long-distance migration and local reproduction, respectively. Finally, we propose future research directions and discuss emerging questions in the area of phenotypic plasticity of locusts.

Migratory herbivorous waterfowl track multiple resource waves during spring migration.

East Asian herbivorous waterfowl intensively use farmland in spring, next to their natural habitat. Accordingly, they might have expanded their migration strategy from merely tracking the green wave of newly emerging vegetation to also incorporating the availability of post-harvest agricultural seeds (here dubbed the seed wave). However, if and how waterfowl use multiple food resources to time their seasonal migration is still unknown. We test this migration strategy using 167 spring migration tracks of five East Asian herbivorous waterfowl species and mixed-effect resource selection function models. We found that all study species arrived at their core stopover sites in the Northeast China Plain after agricultural seeds became available, extended their stay after spring vegetation emerged and arrived at their breeding sites around the emergence of vegetation. At the core stopover sites, all study species used snowmelt as a cue to track seed availability, although smaller-bodied species tended to arrive later. At the breeding sites, swans tracked the onset of vegetation emergence and geese tracked the mid- or end phases of snowmelt. Our findings suggest that waterfowl track multiple resource waves to fine-tune their migration, highlighting new opportunities for conservation.

Host traits rather than migration and molting strategies explain feather bacterial load in Palearctic passerines

Host traits rather than migration and molting strategies explain feather bacterial load in Palearctic passerines

Evidence of longitudinal differences in spring migration strategies of an Arctic-nesting goose.

During spring, migratory birds are required to optimally balance energetic costs of migration across heterogeneous landscapes and weather conditions to survive and reproduce successfully. Therefore, an individual's migratory performance may influence reproductive outcomes. Given large-scale changes in land use, climate, and potential carry-over effects, understanding how individuals migrate in relation to breeding outcomes is critical to predicting how future scenarios may affect populations. We used GPS tracking devices on 56 Greater White-fronted Geese (Anser albifrons) during four spring migrations to examine whether migration characteristics influenced breeding propensity and breeding outcome. We found a strong longitudinal difference in arrival to the breeding areas (18 days earlier), pre-nesting duration (90.9% longer), and incubation initiation dates (9 days earlier) between western- and eastern-Arctic breeding regions, with contrasting effects on breeding outcomes, but no migration characteristic strongly influenced breeding outcome. We found that breeding region influenced whether an individual likely pursued a capital or income breeding strategy. Where individuals fell along the capital-income breeding continuum was influenced by longitude, revealing geographic effects of life-history strategy among conspecifics. Factors that govern breeding outcomes likely occur primarily upon arrival to breeding areas or are related to individual quality and previous breeding outcome, and may not be directly tied to migratory decision-making across broad scales.

The migratory strategies of the Red Knots using the Western Atlantic Flyway as revealed by geolocators

The migratory strategies of the Red Knots using the Western Atlantic Flyway as revealed by geolocators

Pasteurella multocida infection induces blood–brain barrier disruption by decreasing tight junctions and adherens junctions between neighbored brain microvascular endothelial cells

Meningitis induced by Pasteurella multocida has been substantially described in clinical practice in both human and veterinary medicine, but the underlying mechanisms have not been previously reported. In this study, we investigated the influence of P. multocida infection on the permeability of the blood–brain barrier (BBB) using different models. Our in vivo tests in a mouse model and in vitro tests using human brain microvascular endothelial cell (hBMEC) model showed that P. multocida infection increased murine BBB permeability in mice and hBMEC monolayer permeability. Furthermore, we observed that P. multocida infection resulted in decreased expression of tight junctions (ZO1, claudin-5, occludin) and adherens junctions (E-cadherin) between neighboring hBMECs. Subsequent experiments revealed that P. multocida infection promoted the activation of hypoxia inducible factor-1α (HIF-1α)/vascular endothelial growth factor A (VEGFA) signaling and NF-κB signaling, and suppressed the HIF-1α/VEGFA significantly remitted the decrease in ZO1/E-cadherin induced by P. multocida infection (P < 0.001). NF-κB signaling was found to contribute to the production of chemokines such as TNF-1α, IL-β, and IL-6. Additionally, transmission electron microscopy revealed that paracellular migration might be the strategy employed by P. multocida to cross the BBB. This study provides the first evidence of the migration strategy used by P. multocida to traverse the mammalian BBB. The data presented herein will contribute to a better understanding of the pathogenesis of the zoonotic pathogen P. multocida.

Small-Sample Fault Diagnosis of Axial Piston Pumps across Working Conditions, Based on 1D-SENet Model Migration

Hydraulic pumps are the core components that provide power for hydraulic transmission systems, which are widely used in aerospace, marine engineering, and mechanical engineering, and their failure affects the normal operation of the entire system. This paper takes a single axial piston pump as the research object and proposes a small-sample fault diagnosis method based on the model migration strategy for the situation in which only a small number of training samples are available for axial piston pump fault diagnosis. To achieve end-to-end fault diagnosis, a 1D Squeeze-and-Excitation Networks (1D-SENets) model was constructed based on a one-dimensional convolutional neural network and combined with the channel domain attention mechanism. The model was first pre-trained with sufficient labeled fault data from the source conditions, and then, based on the model migration strategy, some of the underlying network parameters were fixed, and a small amount of labeled fault data from the target conditions was used to fine-tune the rest of the parameters of the pre-trained model. In this paper, the proposed method was validated using an axial piston pump fault dataset, and the experimental results show that the method can effectively improve the overfitting problem in the small sample fault diagnosis of axial piston pumps and improve the recognition accuracy.

Live imaging in zebrafish reveals tissue-specific strategies for amoeboid migration.

Amoeboid cells like leukocytes can enter and migrate within virtually every tissue of the body, even though tissues vary widely in their chemical and mechanical composition. Here, we imaged motile T cells as they colonized peripheral tissues during zebrafish development to ask if cells tailor their migration strategy to their local tissue environment. We found that T cells in most sites migrated with f-actin-rich leading-edge pseudopods, matching how they migrate in vitro . T cells notably deviated from this strategy in the epidermis, where they instead migrated using a rearward concentration of f-actin and stable leading-edge blebs. This mode of migration occurs under planar confinement in vitro , and we correspondingly found the stratified keratinocyte layers of the epidermis impose planar-like confinement on leukocytes in vivo . By imaging the same cell type across the body, our data collectively indicates that cells adapt their migration strategy to navigate different tissue geometries in vivo .

Reliability-assured service function chain migration strategy in edge networks using deep reinforcement learning

With the widespread adoption of edge computing and the rollout of 5G technology, the edge network is experiencing rapid growth. Edge computing enables the execution of certain computational tasks on edge devices, fostering more efficient resource utilization. However, the reliability of the edge network is constrained by its network connections. Network instability can significantly compromise service quality. An effective service function chain (SFC) migration algorithm is essential to optimize resource utilization, enhance service quality. This paper begins by analyzing the current research landscape of edge networks and SFC migration algorithms. Subsequently, the challenges associated with edge network and SFC migration are formally articulated, leading to the proposal of a SFC migration algorithm based on deep reinforcement learning (DRL) with a focus on reliability assurance (RA-SFCM). The algorithm leverages multi-agent deep reinforcement learning to dynamically perceive changes in the edge network environment. It introduces an advantage function to evaluate the performance of each agent relative to the average level and incorporates a central attention mechanism with multiple attention heads to better capture the interdependencies and relationships among different agents. Additionally, this paper innovatively defines and quantifies the reliability of the migration process. By introducing a reliability penalty mechanism based on the migration target nodes and link capacity, it enhances the reliability of the migration schemes. The experimental results conclusively demonstrate the remarkable advantages of the RA-SFCM algorithm in terms of real-time performance, resource utilization efficiency, and reliability. Compared to algorithms such as Sa-VNFM, ROVM, and DLTSAC, RA-SFCM exhibits superior performance. For RA-SFCM, the optimized deployment migration strategy enhances real-time performance, precise resource management improves utilization efficiency, and advanced fault tolerance mechanisms strengthen reliability.

Flexible migration by woodland caribou in Ontario, Canada

AbstractRecent studies of ungulate movement ecology suggest that seasonal movement tactics often vary within a population. The forest‐tundra and forest‐dwelling ecotypes of woodland caribou (Rangifer tarandus caribou) in Ontario, Canada, are traditionally presumed to differ in migratory strategy; however, their potential for facultative migration, the practice of interannual switching between migratory and non‐migratory strategies, has yet to be explored. Understanding facultative migration, and any inherent variation and influences could help improve habitat management. We acquired global positioning system (GPS) telemetry‐based movement data from 109 radio‐collared caribou across the Hudson Bay lowlands between 2009 and 2019. We compared the data with estimates of vegetation density, snow cover, and human disturbance to identify environmental influences associated with the probability and magnitude of migration. We also compared seasonal resource selection between migratory and sedentary individuals. Caribou demonstrated plasticity in migration, with evidence of facultative migration by the forest‐tundra and the forest‐dwelling ecotypes. Variation in migration was likely a combination of local adaptation and acute response to changing environmental factors, particularly snow. Probability and distance of migration were positively correlated with snow, while distance also showed spatial dependency. Plasticity in migration has significant implications in relation to future shifts in climate and should be considered in relevant predictive analyses.

A Comparison of the mitochondrial performance between migratory and sedentary mimid thrushes.

Birds exhibit a variety of migration strategies. Because sustained flapping flight requires the production of elevated levels of energy compared to typical daily activities, migratory birds are well-documented to have several physiological adaptations to support the energy demands of migration. However, even though mitochondria are the source of ATP that powers flight, the respiratory performance of the mitochondria is almost unstudied in the context of migration. We hypothesized that migratory species would have higher mitochondrial respiratory performance during migration compared to species that do not migrate. To test this hypothesis, we compared variables related to mitochondrial respiratory function between two confamilial bird species-the migratory Gray Catbird (Dumetella carolinensis) and the non-migratory Northern Mockingbird (Mimus polyglottos). Birds were captured at the same location along the Alabama Gulf Coast, where we assumed that Gray Catbirds were migrants and where resident Northern Mockingbirds live year-round. We found a trend in citrate synthase activity, which suggests that Gray Catbirds have a greater mitochondrial volume in their pectoralis muscle, but we observed no other differences in mitochondrial respiration or complex enzymatic activities between individuals from the migrant versus the non-migrant species. However, when we assessed the catbirds included in our study using well-established indicators of migratory physiology, birds fell into two groups: a group with physiological parameters indicating a physiology of birds engaged in migration and a group with the physiology of birds not migrating. Thus, our comparison included catbirds that appeared to be outside of migratory condition. When we compared the mitochondrial performance of these three groups, we found that the mitochondrial respiratory capacity of migrating catbirds was very similar to that of Northern Mockingbirds, while the catbirds judged to be not migrating were lowest. One explanation for these observations is these species display very different daily flight behaviors. While the mockingbirds we sampled were not breeding nor migrating, they are highly active birds, living in the open and engaging in flapping flights throughout each day. In contrast, Gray Catbirds live in shrubs and fly infrequently when not migrating. Such differences in baseline energy needs likely confounded our attempt to study adaptations to migration.

Genomic structural variation in Barramundi Perch Lates calcarifer and potential roles in speciation and adaptation.

Advancements in genome sequencing and assembly techniques have increased the documentation of structural variants in wild organisms. Of these variants, chromosomal inversions are especially prominent due to their large size and active recombination suppression between alternative homokaryotypes. This suppression enables the 2 forms of the inversion to be maintained and allows the preservation of locally adapted alleles. The Barramundi Perch (BP; Lates calcarifer) is a widespread species complex with 3 main genetic lineages located in the biogeographic regions of Australia and New Guinea (AUS + NG), Southeast Asia (SEA), and the Indian Subcontinent (IND). BP are typically considered to be a protandrous sequential hermaphrodite species that exhibits catadromy. Freshwater occupancy and intraspecific variation in life history (e.g. partially migratory populations) exist and provide opportunities for strongly divergent selection associated with, for example, salinity tolerance, swimming ability, and marine dispersal. Herein, we utilize genomic data generated from all 3 genetic lineages to identify and describe 3 polymorphic candidate chromosomal inversions. These candidate chromosomal inversions appear to be fixed for ancestral variants in the IND lineage and for inverted versions in the AUS + NG lineage and exhibit variation in all 3 inversions in the SEA lineage. BP have a diverse portfolio of life history options that includes migratory strategy as well as sexual system (i.e. hermaphroditism and gonochorism). We propose that the some of the life history variabilities observed in BP may be linked to inversions and, in doing so, we present genetic data that might be useful in enhancing aquaculture production and population management.

Thermal Migration to Recover Spent Pt/C Catalyst.

Recovery of spent Pt/C catalyst is a sustainable low-cost route to promote large-scale application of hydrogen fuel cells. Here, we report a thermal migration strategy to recover the spent Pt/C. In this route, the ZIF-8 is used to produce nitrogen doped porous carbon (NC) with abundant pyrimidine nitrogen sites as the new support. Subsequently, the spent Pt/C, NC, and NH4Cl etching reagent are mixed and heated at 900 °C to thermally migrate Pt from Pt/C onto NC with the help of NH4Cl etching reagent. The thermal-volatilized Pt tends to be captured by the pyrimidine nitrogen sites of NC support, thus producing the Pt clusters or 4-5 nm Pt particles. The recovered Pt/NC catalyst exhibits the highly stable oxygen reduction activities with a mass activity of 0.6 A mgPt -1 after 30000-cycle accelerated durability test.

Seasonal migration patterns of Siberian Rubythroat (Calliope calliope) facing the Qinghai–Tibet Plateau

BackgroundSmall songbirds respond and adapt to various geographical barriers during their annual migration. Global flyways reveal the diverse migration strategies in response to different geographical barriers, among which are high-elevation plateaus. However, few studies have been focused on the largest and highest plateau in the world, the Qinghai–Tibet Plateau (QTP) which poses a significant barrier to migratory passerines. The present study explored the annual migration routes and strategies of a population of Siberian Rubythroats (Calliope calliope) that breed on the north-eastern edge of the QTP.MethodsOver the period from 2021 to 2023, we applied light-level geolocators (13 deployed, seven recollected), archival GPS tags (45 deployed, 17 recollected), and CAnMove multi-sensor loggers (with barometer, accelerometer, thermometer, and light sensor, 20 deployed, six recollected) to adult males from the breeding population of Siberian Rubythroat on the QTP. Here we describe the migratory routes and phenology extracted or inferred from the GPS and multi-sensor logger data, and used a combination of accelerometric and barometric data to describe the elevational migration pattern, flight altitude, and flight duration. All light-level geolocators failed to collect suitable data.ResultsBoth GPS locations and positions derived from pressure-based inference revealed that during autumn, the migration route detoured from the bee-line between breeding and wintering grounds, leading to a gradual elevational decrease. The spring route was more direct, with more flights over mountainous areas in western China. This different migration route during spring probably reflects a strategy for faster migration, which corresponds with more frequent long nocturnal migration flights and shorter stopovers during spring migration than in autumn. The average flight altitude (1856 ± 781 m above sea level) was correlated with ground elevation but did not differ between the seasons.ConclusionsOur finding indicates strong, season-dependent impact of the Qinghai–Tibet Plateau on shaping passerine migration strategies. We hereby call for more attention to the unexplored central-China flyway to extend our knowledge on the environment-migration interaction among small passerines.

Sex-specific migration strategies and underlying physiology contribute to spring arrival protandry in a songbird

Sex-specific migration strategies and underlying physiology contribute to spring arrival protandry in a songbird

Adaptive task migration strategy with delay risk control and reinforcement learning for emergency monitoring

The timely and reliable handling of post-disaster emergency monitoring tasks is crucial for effective rescue operations. UAV-assisted edge computing plays a pivotal role in the rapid deployment of such systems. However, challenges persist due to communication and computation resource bottlenecks when dealing with delay-sensitive monitoring tasks. In dynamic post-disaster environments, effective task scheduling and resource allocation decisions directly impact the system’s ability to process tasks. Therefore, this paper proposes an adaptive task migration decision-making system for emergency monitoring tasks in UAV-assisted edge computing. Firstly, We decomposed the optimization objectives based on the task processing workflow, then devised a stepwise delay risk control and resource recovery mechanism based on early discarding. Secondly, by integrating multi-agent reinforcement learning (MARL), optimal strategies for task offloading, UAV queue scheduling, and communication resource allocation are learned to enhance the decision system’s environmental awareness and maximize the successful completion of emergency monitoring tasks. Simulation experiments demonstrate that the algorithm significantly improves the success rate of migration tasks and data processing capacity, thereby validating its convergence and effectiveness.

Moving to mate? Migration strategy does not predict genetic structure or diversity in bats (Chiroptera)

Abstract How, when, and where animals move during mating periods directs gene-flow patterns across landscapes. Traits associated with movement, such as movement ability and migratory behaviour, are sometimes correlated with population genetic structure, but this relationship depends on where and when mating occurs relative to annual movements. With their wide diversity in behaviours and life-history strategies, bats provide a testing ground for hypotheses about population structure related to migration and mating. We used a global sample of microsatellite data (N = 233 sampling locations from 17 bat species) associated with published studies to examine links between genetic variation and short-distance, long-distance, or non-migratory strategies that also relate to varied mating strategies. The genetic measures we tested were population-specific differentiation, gene diversity, and allelic richness. Using Bayesian models that accounted for phylogenetic distances among species and spatial autocorrelation, we identified no correlations between migration strategy and genetic variation. Our results suggest that hypotheses about genetic structure being mediated by migration might not hold, in general, for bat species. We discuss the need for continued research into the complex association of ecological, biogeographical, and behavioural factors that facilitate gene flow among populations, especially in species with diverse movement patterns.

Plant litter as a heavy metal migration strategy following application of sewage sludge to subtropical forest soils

The environmental risks of migration of heavy metals (HMs) following applications of sewage sludge (SS) to forest soils are garnering increased attention. Plant litter at the forest floor may modify HM migration pathways through impacts on soil aggregates and water/soil erosion; however, HM migration responses to plant litter are poorly understood. The aim of this study was to determine the effects of plant litter cover on HMs migration, and water and soil erosion following the application of SS to subtropical forest soils. Effects of addition of SS along and SS plus plant litter at 0.75 or 1.5 kg m−2 on the migration of cadmium, chromium, copper, nickel, lead, and zinc in surface runoff, soil interflow, and sediments were quantified across nine simulated rainfall events in a laboratory experiment and following natural intense rain events in a field experiment. Addition of SS elevated HM concentrations in surface runoff by 38.7 to 98.5 %, in soil interflow by 48.3 to 312.5 %, and in sediment by 28.5 to 149.4 %, and increased the production of sediment aggregates <0.05 mm that led to greater cumulative migrations of HMs in surface runoff and sediment; sediment accounted for 89.5 % of HM migrations. Addition of plant litter reduced cumulative migration of HMs by 87.1–97.27 %; however, the higher rate of plant litter led to a decrease in surface runoff and sediment yield, and an increase in soil interflow. Addition of plant litter shifted the main pathway of HM migration from sediment to surface runoff and soil interflow. The potential ecological HM risk index was “low” for each treatment. We found consistency in HM concentrations and migrations via surface runoff between the field and laboratory experiments. Overall, the addition of plant litter with SS mitigated soil erosion and reduced total migration of HMs, resulting in a 88.7–97.3 % decrease in the ecological risk index of the six HMs. We conclude that the addition of plant litter may provide a management strategy for the mitigation of HM risks to environmental safety for the disposal of SS in subtropical forest systems.

High-resolution cropland mapping in China’s Huang-Huai-Hai Plain: The coupling of machine learning methods and prior information

Numerous map products containing cropland data are currently available. However, due to their low temporal and spatial resolutions and limited accuracy, their practical applications are limited. Thus, research on the precise mapping of croplands with high temporal and spatial resolutions is still urgently needed. The Huang-Huai-Hai Plain, a critical grain production area in China, was used as the research area to produce high-resolution annual cropland maps from 2018 to 2022. Sentinel-2 imagery, digital elevation model (DEM) data, and China Agricultural Ecological Zoning (CAEZ) data were collected. Based on these data, the study area was stratified into different zones, and then the distinct characteristics and optimal timing for differentiating cropland from other land cover types within each zone were analyzed and used as prior information for guiding time-series image compositing. Furthermore, the spectral information divergence (SID) index was used to modify the existing sample migration technique to transfer training samples across years. Via the Google Earth Engine (GEE) platform, the random forest (RF) classification method and positive and unlabeled learning (PUL) method were combined to construct cropland maps from composited images and terrain information from DEMs. Compared with the seasonal or spectral-temporal metric (STM) image composition methods, the image composition method based on prior information significantly improved the distinction between cropland and other land cover types. Moreover, the newly proposed sample migration strategy substantially increased the accuracy of training samples transferred across years. Compared with existing cropland maps from products such as the ESA, ESRI, GlobeLand30, GLAD, and CLCD, the cropland maps generated in this study demonstrated superior accuracy, with average overall accuracy (OA) values from 88.81% to 91.66% for different zones, thus outperforming other products with OA values from 77.53% to 88.90%. This study supports the development of related agricultural and ecological research and provides a valuable reference for cropland mapping.