Migratory animals couple biodiversity and ecosystem functioning worldwide

Inter- and intraspecific variation in the degree of marine-derived resources of amphidromous fishes

Migratory animals often transport allochthonous materials, energy or organisms from donor to recipient ecosystems, thereby affecting the dynamics of consumers, communities and ecosystems in the recipient systems. The biomass of migrants is commonly assumed to be equal to that of the allochthonous materials they transport, with the inherent assumption that migrant bodies are produced purely from allochthonous resources. However, the extent to which the body composition of many migratory animals consists of allochthonous materials [e.g., the proportion of total body mass consisting of allochthonous resources, hereafter degree of allochthony (DOA)] may gradually decrease if the animals consume autochthonous resources during their migration. Ignoring this process leads to an overestimation of the magnitude and temporal features of material subsidies. In this study, we quantified the DOA of nine amphidromous fish species that migrate from marine to rivers, using the sulphur stable isotope (δ34S) analysis. The DOA varied substantially among species (11%-82%) and even within species (Sicyopterus japonicus had the highest DOA: 22%-97%). Species with larger body sizes tended to exhibit a lower DOA. This trend was also observed at the species level for six of the nine species, with five species showing an additional pattern of later migrating individuals with lower DOA. These results imply that quantifying DOA is important for accurately estimating material subsidies across ecosystems, owing to the upstream migration of amphidromous fish. Life-history studies of amphidromous fishes are crucial for elucidating the mechanisms behind inter- and intraspecific variation in DOA, which ultimately contributes to a better understanding of marine-river ecosystem linkages mediated by these fishes.

Ecosystems have multiple interacting processes that buffer against co-occurring stressors

There are multiple processes that buffer the effects of anthropogenic stressors. Much is known about how single buffering processes (e.g., biodiversity, adaptation) mitigate the effects of stressors on ecosystem properties and functions, but how multiple buffering processes combine to mitigate the effects of multiple co-occurring stressors is poorly understood. We outline how single processes (e.g., cross-tolerance) can buffer the effects of multiple stressors, whereas multiple buffering processes can act jointly across ecological and temporal scales to reduce the effects of single or multiple stressors. Synergistic interactions between multiple buffering processes can further enhance ecosystem resistance to multiple stressors. A wider awareness of interacting buffering processes in ecosystems will enhance our understanding of ecosystem stability in the face of multiple stressors.

Will I stay or will I go? Eye morphology predicts individual migratory propensity in a partial migrant

Billions of animals undertake migratory journeys every year, with powerful consequences for ecosystem dynamics. Key behaviours that enable successful migration are often guided by the visual system. The amount and quality of information that animals can extract from visual scenes are directly related to structural eye size-larger eyes can house larger pupils, enhancing light-gathering capacity and vision by improving visual acuity and contrast sensitivity. Migration should exert strong demands on individual visual performance, for example via foraging, antipredator benefits or navigational requirements. Yet, it remains elusive whether variations in eye morphology and corresponding visual capabilities are associated with migratory propensity. Here, we capitalize upon intra-population variation in migratory propensity (also known as partial migration) in roach, a common freshwater fish, to directly test for migration-associated variation in image-forming eyes within a species. In a multi-year field study tracking the migration decisions of over 2000 individuals in two different lake systems, we found that relative pupil size was positively associated with individual migration propensity. Computational simulations of the visual ecology associated with the observed differences in pupil size show that migrants have an extended visual detection range and that the performance gain is most pronounced for viewing small targets (e.g. planktonic prey) under low-light conditions. These results suggest that the larger pupils of migrants represent an adaptation for increased foraging efficiency to aid in the accumulation of critical pre-migratory energy reserves. Together, our anatomical and functional findings provide new perspectives on visual system design in relation to individual-level migratory decision-making.

Mechanisms underlying the loss of migratory behaviour in a long-lived bird

Human-induced environmental changes are changing the migration patterns of birds worldwide. Species are adjusting migration timing, shortening and diversifying migratory routes or even transitioning towards residency. While the ultimate causes driving changes in migratory patterns are well established, the underlying mechanisms by which migratory species adapt to environmental change remain unclear. Here, we studied the mechanisms driving the recent and rapid loss of migratory behaviour in Iberian white storks Ciconia ciconia, a long-lived and previously fully migratory species through the African-Eurasian flyway. We combined 25 years of census data, GPS-tracking data from 213 individuals (80 adults and 133 first-year juveniles) tracked up to 7 years and whole-genome sequencing to disentangle whether within- (phenotypic flexibility) or between- (developmental plasticity or microevolution, through selection) individual shifts in migratory behaviour over time explain the observed population-level changes towards residency. Between 1995 and 2020, the proportion of individuals no longer migrating and remaining in Southern Europe year-round increased dramatically, from 18% to 68-83%. We demonstrate that this behavioural shift is likely explained by developmental plasticity. Within first-year birds, 98% crossed the Strait of Gibraltar towards their African wintering grounds, in Morocco or Sub-Saharan Africa. However, the majority shifted towards a non-migratory strategy as they aged-the proportion of migrants decreased to 67% and 33%, in their second and third year of life, respectively. Supporting these findings, only 19% of GPS-tracked adults migrated. We did not find evidence of phenotypic flexibility, as adults were highly consistent in migratory behaviour over multiple years (only 3 individuals changed strategy between years, out of 113 yearly transitions), nor of selection acting on genetic variation, since genomes of adult migrants and residents are essentially undifferentiated and we did not find evidence of selective sweeps in resident birds. Our results suggest that through developmental plasticity, traits that are plastic during specific windows of development become fixed during adulthood. Thus, inter-generational shifts in the frequency of migratory and non-migratory young individuals could drive population changes in migratory behaviour. This can provide a mechanism for long-lived migratory birds to respond to rapid human-driven environmental changes.

A call for increased integration of experimental approaches in movement ecology

Rapid developments in animal-tracking technology have enabled major advances in the field of movement ecology, which seeks to understand the drivers and consequences of movement across scales, taxa, and ecosystems. The field has made ground-breaking discoveries, yet the majority of studies in movement ecology remain reliant on observational approaches. While important, observational studies are limited compared to experimental methods that can reveal causal relationships and underlying mechanisms. As such, we advocate for a renewed focus on experimental approaches in animal movement ecology. We illustrate a way forward in experimental movement ecology across two fundamental levels of biological organisation: individuals and social groups. We then explore the application of experiments in movement ecology to study anthropogenic influences on wildlife movement, and enhance our mechanistic understanding of conservation interventions. In each of these examples, we draw upon previous research that has effectively employed experimental approaches, while highlighting outstanding questions that could be answered by further experimentation. We conclude by highlighting the ways experimental manipulations in both laboratory and natural settings provide a promising way forward to generate mechanistic understandings of the drivers, consequences, and conservation of animal movement.

Protected areas mitigate the reduction in habitat suitability for swans under climate change: A case study in the Yellow River Basin

Changes in migratory birds' habitats are important indicators of the health of global ecosystems. However, the habitat dynamics of the flagship swan species in China's major river basins and the adaptive strategies these species employ to respond to climate change have remained unclear. Using citizen science data, survey data, and species distribution models, we explored how three future climate scenarios for 2040-2060 affect habitat suitability for migratory swans in the Yellow River Basin. We also evaluated the role of protected areas (PAs) in mitigating the negative impacts of climate change. We found that (1) under current climate conditions, the Mute Swan (Cygnus olor), the Bewick's Swan (Cygnus columbianus bewickii), and the Whooper Swan (Cygnus cygnus) occupy substantial suitable habitats, with the Whooper Swan having the most extensive range. (2) the Mute Swan and the Bewick's Swan were predicted to experience the largest habitat loss under the high-emission scenario, while the Whooper Swan would benefit from climate change by gaining suitable habitat, especially under the medium-emission scenario. (3) PAs were most effective in mitigating the adverse effects of climate change on habitat suitability for the Mute Swan, followed by the Whooper Swan, with limited mitigating effect for the Bewick's Swan. These findings highlight the need for species-specific conservation strategies and the critical role of PAs in preserving habitat suitability under climate change.

The silver king in the Magic City: Observation of Atlantic tarpon Megalops atlanticus aggregation off Miami, Florida

Due to the logistical and financial challenges in studying migratory marine species, there is relatively limited knowledge of the reproductive biology, behavior, and habitat use of many ecologically important marine megafauna species, including the Atlantic tarpon Megalops atlanticus. Here, we present a novel observation using consumer-grade aerial drones to observe, quantify the scale of, and classify behaviors within a previously unreported tarpon aggregation (N = 182) over the course of a 2-day fish aggregation event. After the event, we analysed and compared observed behaviors (e.g., cruising and clustering) with those of other fish species with well-documented reproductive behaviors, revealing behaviors potentially consistent with courtship, leading us to believe this to be a possible spawning aggregation or aggregation of reproductive/migratory significance. This aggregation occurred in highly altered and urbanized habitat off the coast of South Florida, during the winter, and outside of tarpon's previously reported spring and summer spawning season. Although few studies to date have used drones to monitor teleosts, this study reinforces their potential value as a tool for monitoring fish populations, behavior, and movement.

Climate change is leading to an ecological trap in a migratory insect

Many insect migrants rely on favorable seasonal winds to carry out long-range latitudinal migrations. In East China, the annual advance and retreat of the East Asian summer monsoon produces ideal conditions for seasonal range expansion and contraction of many migratory crop pests. However, climate-induced changes in the strength, timing, and location of the monsoon are impacting wind systems which may, in turn, affect migration patterns. We investigated these questions in the rice leafroller (RLR) moth, a severe pest of rice that annually invades the Lower Yangtze River Valley (LYRV) of China from winter-breeding areas further south. Using a 24-y dataset of RLR population dynamics from 31 monitoring stations across Southeast China, we investigated the impact of changes in monsoon wind regimes on fall migration patterns of the pest. Historically, RLR emigrated from the LYRV to South China on the favorably directed winds produced by the retreat of the monsoon at the end of the outbreak season (from mid-August onward). We show that in the recent 12-y period, prevailing late-season winds remain northward for longer than previously, preventing locally produced moths from emigrating southward. Additionally, winds now facilitate mass late-season immigrations into the LYRV, creating an ecological trap, as immigrants do not have time to produce another generation. As a consequence of the changing wind patterns, pest pressure is declining, and climate-induced changes to the East Asian summer monsoon result in seasonal migration becoming a riskier strategy. Such changes in insect migration patterns have severe implications for the population dynamics of windborne migrants, ecosystem functioning, and pest management strategies.

A review of migratory Alosidae marine ecology in the northwest Atlantic

Migratory animals play a crucial role in connecting distinct habitats by transferring matter and energy across ecosystem boundaries. In the North Atlantic, anadromous species exemplify this through their movement between freshwater and marine environments. Alosids, including species such as alewife (Alosa pseudoharengus), blueback herring (Alosa aestivalis), and American shad (Alosa sapidissima), exhibit this migratory behavior to maximize growth and fecundity and are, therefore, vital components of Atlantic coastal ecosystems. Despite their ecological importance, these species have experienced considerable population declines. Due to a research focus on dams and the freshwater phase of their ecology, the marine ecology of Alosids remains much less understood, potentially hindering effective management. This paper synthesizes current knowledge on the marine ecology of anadromous alewife, blueback herring, and American shad in the northwest Atlantic, focusing on life-history aspects, migratory patterns, and foraging behavior at sea. The paper also outlines current fisheries management and the anthropogenic threats these species face during their marine phase. We identified knowledge gaps regarding marine distribution, migration routes, impacts of climate change on movement and behavior, population dynamics, and the identification of gaspereau. By identifying gaps in the literature, we highlight research needs, emphasizing the role of telemetry studies in tracking marine movements and the impact of climate change on habitat use. Addressing these gaps through targeted research on marine ecology and movement patterns is essential for developing informed management strategies aimed at increasing Alosid populations.

Multispecies migratory connectivity indicates hemispheric-scale risk to bird populations from global change

Global agreements to reduce the extinction risk of migratory species depend critically on intersecting migratory connectivity-the linking of individuals between regions in different seasons-and spatial patterns of environmental change. Here we integrate movement data from >329,000 migratory birds of 112 species to develop a parameter representing exposure to global change: multispecies migratory connectivity. We then combine exposure with projected climate and land-cover changes as a measure of hazard and species conservation assessment scores as a metric of vulnerability to estimate the relative risk of migratory bird population declines across the Western Hemisphere. Multispecies migratory connectivity (exposure) is the strongest driver of risk relative to hazard and vulnerability, indicating the importance of synthesizing connectivity across species to comprehensively assess risk. Connections between breeding regions in Canada and non-breeding regions in South America are at the greatest risk, which underscores the particular susceptibility of long-distance migrants. Over half (54%) of the connections categorized as very high risk include breeding regions in the eastern United States. This three-part framework serves as an ecological risk assessment designed specifically for migratory species, providing both decision support for global biodiversity conservation and opportunities for intergovernmental collaboration to sustain migratory bird populations year-round.

Radar-measured passerine vertical speeds reveal a migratory switch near a major barrier

Successful accomplishment of long-distance migration necessitates optimal decision-making processes. Throughout their migration, birds need to constantly choose to fly or to stop. Passerine migrants integrate internal (e.g., lipid deposition) and external (e.g., prevailing winds) factors resulting in specific departure or landing times. We calculated individual departure and landing timing using vertical-looking radar in the Hula Valley, compiled nightly departure and landing ratios (departure and landing amounts relative to total migration flux), and explored how these are affected by meteorological conditions. Crosswind direction emerged as a key factor affecting departure and landing decisions during autumn migration in the area. Birds avoided drifting toward the Mediterranean Sea by landing and preferred taking off when winds blew away from the sea. Our findings represent an undescribed migration initiation and termination switch with implications for flight and stopover scheduling. The method extends the scope of aeroecological research for addressing individual-level migration behavior.

Expanding protected area coverage for migratory birds could improve long-term population trends

Populations of many migratory taxa have been declining over recent decades. Although protected areas are a cornerstone for conservation, their role in protecting migratory species can be incomplete due to the dynamic distributions of these species. Here, we use a pan-European citizen science bird occurrence dataset (EurobirdPortal) with Spatiotemporal Exploratory Modelling to assess how the weekly distributions of 30 passerine and near passerine species overlap with protected areas in Europe and compare this to range adjusted policy protection targets. Thirteen of our 30 species were inadequately covered by protected areas for some, or all, of the European part of their annual cycle under a target based on the 2020 Convention on Biodiversity framework and none were adequately covered under a target based on the 2030 Convention on Biodiversity framework. Species associated with farmland had the lowest percentage of their weekly distribution protected. The percentage of a species' distribution within protected areas was positively correlated with its long-term population trend, even after accounting for confounding factors, suggesting a positive influence of protected areas on long-term trends. This emphasises the positive contribution that an informed expansion of the European protected area system could play for the future conservation of migratory land birds.

Integrating Network and Meta-Ecosystem Models for Developing a Zoogeochemical Theory

Human activities have caused significant changes in animal abundance, interactions, movement and diversity at multiple scales. Growing empirical evidence reveals the myriad ways that these changes can alter the control that animals exert over biogeochemical cycling. Yet a theoretical framework to coherently integrate animal abundance, interactions, movement and diversity to predict when and how animal controls over biogeochemical cycling (i.e., zoogeochemistry) change is currently lacking. We present such a general framework that provides guidance on linking mathematical models of species interaction and diversity (network theory) and movement of organisms and non-living materials (meta-ecosystem theory) to account for biotic and abiotic feedback by which animals control biogeochemical cycling. We illustrate how to apply the framework to develop predictive models for specific ecosystem contexts using a case study of a primary producer-herbivore bipartite trait network in a boreal forest ecosystem. We further discuss key priorities for enhancing model development, data-model integration and application. The framework offers an important step to enhance empirical research that can better inform and justify broader conservation efforts aimed at conserving and restoring animal populations, their movement and critical functional roles in support of ecosystem services and nature-based climate solutions.

Qiviut Trace and Macro Element Profile Reflects Muskox Population Trends

Understanding the drivers influencing ungulate population dynamics is crucial for developing conservation and management strategies to support wildlife health. Trace and macro elements are vital for ungulate growth, reproduction and survival. Thus, the trajectory of wildlife populations may be associated with element imbalances. Element concentrations can be measured in hair, an increasingly recognised bio-monitoring tool. However, a better understanding of the relevance for wild ungulate population dynamics is needed. This study aimed to assess if element profiles in hair reflected the population trajectory of a keystone Arctic ungulate, muskox Ovibos moschatus, and whether benchmarks could be defined for element concentrations to assess population status. We measured qiviut (hair) element concentrations of 11 muskox populations ranging across northern America, including Greenland, and evaluated the association between element concentrations and different population trajectories. Seven trace and macro elements differentiated increasing populations from declining and stable populations using linear discriminant analysis. In general, copper, selenium, iron, manganese and cobalt tended to be at higher concentrations in increasing populations, whereas zinc and calcium were generally at lower concentrations in these populations, though variations were observed among populations. Benchmarks were defined for copper, selenium and iron, indicating populations were more likely to decline below a threshold concentration of these elements ('limit') and increase above a threshold concentration ('target'). 'Limit' benchmarks were defined for zinc and calcium where populations were more likely to be increasing below this threshold value. Hair element profiles are a useful indicator of population trajectory in wild ungulate populations. Identified benchmarks can be used to assess population status, complementing ongoing but irregular and expensive monitoring efforts like population surveys, while trace element concentrations can provide insights into the mechanisms driving population change. Hair samples can easily be collected non-invasively or alongside other monitoring activities, enhancing proactive wildlife management and conservation.

Predicting the impact of targeted fence removal on connectivity in a migratory ecosystem

Fencing is one of the most widely utilized tools for reducing human-wildlife conflict in agricultural landscapes. However, the increasing global footprint of fencing exceeds millions of kilometers and has unintended consequences for wildlife, including habitat fragmentation, movement restriction, entanglement, and mortality. Here, we present a novel and quantitative approach to prioritize fence removal within historic migratory pathways of white-bearded wildebeest (Connochaetes taurinus) across Kenya's Greater Masai Mara Ecosystem. Our approach first assesses historic and contemporary landscape connectivity of wildebeest between seasonal ranges by incorporating two sets of GPS tracking data and fine-scale fencing data. We then predict connectivity gains from simulated fence removal and evaluate the impact of different corridor widths and locations on connectivity and removal costs derived from locally implemented interventions. Within the study system, we found that modest levels of fence removal resulted in substantial connectivity gains (39%-54% improvement in connectivity for 15-140 km of fence line removed). By identifying the most suitable corridor site, we show that strategically placed narrow corridors outperform larger, more expensive interventions. Our results demonstrate how and where targeted fence removal can enhance connectivity for wildlife. Our framework can aid in identifying suitable and cost-effective corridor restoration sites to guide decision-makers on the removal of fences and other linear barriers. Our approach is transferable to other landscapes where the removal or modification of fences or similar barriers is a feasible mitigation strategy to restore habitat and migratory connectivity.

Multiple drivers of spring migration timing for red deer over the past 16 years in northern Europe

The timing of migration is fundamental for species exploiting seasonally variable environments. For ungulates, earlier spring migration is expected with earlier vegetation green-up. However, other drivers, such as access to agricultural farmland and variation in local conditions, are also known to affect migration. We investigated the timing of spring migration for 96 male and 201 female red deer (Cervus elaphus) using a long-term dataset (2005-2020). Overall, the timing of migration was mainly characterized by large individual variability between and within years (95% range 6 April to 18 June). The spring migration timing was, as expected, later with colder winter and spring conditions (North Atlantic Oscillation (NAO) winter and April indices) and later peak vegetation green-up (NDVI), with a five-day delay in green-up causing a migration delay of 1.2 days. Timing was also influenced by local conditions in summer and winter home ranges. Red deer with greater access to farmland and a more variable topography (hence variable plant phenology) in winter delayed migration. Similarly, individuals with higher-elevation summer ranges (with delayed onset of plant growth) also delayed migration. Our analyses highlight that the timing of red deer migration is determined by multiple drivers affecting foraging conditions in the landscape, indicative of considerable phenotypic plasticity.

Aggregative responses of marine predators to a pulsed resource

Pulsed resources resulting from animal migrations represent important, transient influxes of high resource availability into recipient communities. The ability of predators to respond and exploit these large increases in background resource availability, however, may be constrained when the timing and magnitude of the resource pulse vary across years. In coastal Newfoundland, Canada, we studied aggregative responses of multiple seabird predators to the annual inshore pulse of a key forage fish species, capelin (Mallotus villosus). Seabird aggregative responses to fish biomass were quantified from weekly hydroacoustic and seabird surveys during July-August within an annually persistent foraging area (10 km2) associated with a cluster of capelin spawning sites across 10 years (2009-2010, 2012, 2014-2020). Seabird predators included breeding members of the families Alcidae (Common Murres Uria aalge, Razorbills Alca torda, Atlantic Puffins Fratercula arctica) and Laridae (Great Black-backed Gulls Larus marinus, American Herring Gulls L. argentatus smithsonianus) and Northern Gannets Morus bassanus, along with non-breeding, moulting members of the Family Procellariidae (Sooty Shearwaters Ardenna griseus, Great Shearwaters A. gravis). The inshore migration of spawning capelin resulted in 5-619 times (mean ± SE, 146 ± 59 times) increase in coastal fish biomass along with a shift towards more, larger and denser fish shoals. Within years, seabird abundance did not increase with inshore fish biomass but rather peaked near the first day of spawning, suggesting that seabirds primarily respond to the seasonal resource influx rather than short-term variation in fish biomass. Across years, the magnitude of the seabird aggregative response was lower during low-magnitude resource pulse years, suggesting that predators are unable to perceive low-magnitude pulses, avoid foraging under high competitor densities, and/or shift dietary reliance away from capelin under these conditions. The seabird response magnitude, however, was higher when the resource pulse was delayed relative to the long-term average, suggesting that predators increase exploitation during years of minimal overlap between the resource pulse and energetically demanding periods (e.g. breeding, moulting). This long-term study quantifying responses of multiple predators to a pulsed resource illustrates the ability of natural systems to tolerate natural and human-induced disturbance events.

Genotype But Not Body Shape Predicts River Migration Success in Atlantic Salmon

Migratory species typically undertake demanding long-distance journeys, across different habitat types during which they are exposed to multiple natural and anthropogenic stressors. Mortality during migration is typically high and may be human induced. Understanding individual responses to these selection pressures is rarely attempted because of the challenges of relating individual phenotypic and genetic data to migration success. Here, we show distinct single nucleotide polymorphism (SNP) sets significantly differentiated between Atlantic salmon smolts making successful migrations to sea and those that failed to migrate, in two different rivers. In contrast, morphological variation was not diagnostic of migration success. Populations from each river were genetically distinct, and while different genes were possibly implicated in migration success in each river, they related to common biological processes (e.g., osmoregulation and immune and stress response). Given that migration failure should quickly purge polymorphism at selected SNPs from a population, the question of how genetic diversity in these populations is maintained is an important one. Standing genetic variation could be maintained by different life history strategies and/or environmentally driven balancing selection. Our work highlights the importance of preserving genetic diversity to ensure evolutionary resilience at the population level and has practical implications for management.

The Influence of Microbiota on Wild Birds' Parental Coprophagy Behavior: Current Advances and Future Research Directions

This comprehensive review provides an in-depth exploration of the intriguing phenomenon of parental coprophagy in wild birds and its profound implications on the influence of adult avian parents' health. This review investigates the composition and dynamics of avian feces' microbiota, casting light on the various dietary, environmental, and genetic factors that influence its diversity. Furthermore, it emphasizes parental coprophagy, a behavior observed in numerous bird species, particularly among herbivorous and passerine birds. The review investigates multiple hypotheses proposed to explain the occurrence of coprophagy. It delves into its function as a potential mechanism for transmitting microorganisms, particularly feces bacteria, from nestlings to their parents. This microbial transfer may affect the health and well-being of adult avian parents. In addition, the review highlights the current research deficits and debates surrounding coprophagy. These gaps include crucial aspects such as the onset of coprophagy, its long-term effects on both parents and offspring, the nutritional implications of consuming nestling feces, the potential risks of pathogen transmission, and the ecological and evolutionary factors that drive this behavior. As the review synthesizes existing knowledge and identifies areas requiring additional research, it emphasizes the significance of future studies that comprehensively address these gaps. By doing so, we can understand coprophagy's ecological and evolutionary significance in wild birds, advancing our knowledge on avian biology. This information can improve conservation efforts to protect migratory bird populations and their complex ecosystems.

Identifying signals of memory from observations of animal movements

Incorporating memory (i.e., some notion of familiarity or experience with the landscape) into models of animal movement is a rising challenge in the field of movement ecology. The recent proliferation of new methods offers new opportunities to understand how memory influences movement. However, there are no clear guidelines for practitioners wishing to parameterize the effects of memory on moving animals. We review approaches for incorporating memory into step-selection analyses (SSAs), a frequently used movement modeling framework. Memory-informed SSAs can be constructed by including spatial-temporal covariates (or maps) that define some aspect of familiarity (e.g., whether, how often, or how long ago the animal visited different spatial locations) derived from long-term telemetry data. We demonstrate how various familiarity covariates can be included in SSAs using a series of coded examples in which we fit models to wildlife tracking data from a wide range of taxa. We discuss how these different approaches can be used to address questions related to whether and how animals use information from past experiences to inform their future movements. We also highlight challenges and decisions that the user must make when applying these methods to their tracking data. By reviewing different approaches and providing code templates for their implementation, we hope to inspire practitioners to investigate further the importance of memory in animal movements using wildlife tracking data.

Individual return patterns of spawning flannelmouth sucker (Catostomus latipinnis) to a desert river tributary

Tributaries provide temporal and spatial habitat heterogeneity in river networks that can be critical for parts of the life history of a species. Tributary fidelity can benefit individual fish undergoing spawning migrations by reducing time and energy spent exploring new areas and leveraging previous experience, but anthropogenic activities that fragment or degrade these systems can eliminate those benefits. We used multistate models based on passive integrated transponder (PIT) detection data from 2013 to 2023 to estimate the proportion of flannelmouth suckers (Catostomus latipinnis) migrating to a tributary, McElmo Creek, from the mainstem San Juan River for spawning. Survival varied among years and among states. The top model for migration probability included sex, with males slightly more likely to migrate (0.93 vs 0.90), and the next model identified interannual variation in migration probability ranging from 0.875 to 0.999 across years, indicating high site fidelity. Individuals showed consistency in relative arrival timing across years, with the highest correlation generally during years with greater spring discharge and extended tributary residence time. Successful tributary spawning may be important for the maintenance of the mainstem San Juan River flannelmouth sucker population, but site fidelity may be maladaptive where tributaries are vulnerable to human alterations.

Sequential migrations of diverse fish community provide seasonally prolonged and stable nutrient inputs to a river

Animal migrations transport resources among spatially separate ecosystems, effectively linking them. In freshwater ecosystems, numerous fish species migrate between mainstream rivers or lakes and their tributaries, providing resources and nutrients during their spawning migrations. Multiple migratory species travel to the same destinations and contribute such nutrients, but knowledge remains limited about how the diversity of migratory animals influences the recipient ecosystem. We investigated how migrations of diverse fish community from Lake Biwa, Japan contribute to nutrient inputs in one of the lake's tributary rivers and how they influence the ecosystem. Sequential migration of six fish species continued for 8 months of a year, causing high-level nutrient concentration and primary production. The fish-derived resources were taken up by diverse members of the river community. Our results emphasize the extent to which migrations of diverse animals seasonally extend and stabilize the resource subsidy and how they extend pronounced effects on the recipient ecosystems.

Continental-scale nutrient and contaminant delivery by Pacific salmon

The movement of large amounts of nutrients by migrating animals has ecological benefits for recipient food webs1,2 that may be offset by co-transported contaminants3,4. Salmon spawning migrations are archetypal of this process, carrying marine-derived materials to inland ecosystems where they stimulate local productivity but also enhance contaminant exposure5-7. Pacific salmon abundance and biomass are higher now than in the last century, reflecting substantial shifts in community structure8 that probably altered nutrient versus contaminant delivery. Here we combined nutrient and contaminant concentrations with 40 years of annual Pacific salmon returns to quantify how changes in community structure influenced marine to freshwater inputs to western North America. Salmon transported tonnes of nutrients and kilograms of contaminants to freshwaters annually. Higher salmon returns (1976-2015) increased salmon-derived nutrient and contaminant inputs by 30% and 20%, respectively. These increases were dominated by pink salmon, which are short-lived, feed lower in marine food webs than other salmon species, and had the highest nutrient-to-contaminant ratios. As a result, the delivery of nutrients increased at a greater rate than the delivery of contaminants, and salmon inputs became more ecologically beneficial over time. Even still, contaminant loadings may represent exposure concerns for some salmon predators. The Pacific salmon example demonstrates how long-term environmental changes interact with nutrient and contaminant movement across large spatial scales and provides a model for exploring similar patterns with other migratory species9.

Seasonality Structures Avian Functional Diversity and Niche Packing Across North America

Assemblages in seasonal ecosystems undergo striking changes in species composition and diversity across the annual cycle. Despite a long-standing recognition that seasonality structures biogeographic gradients in taxonomic diversity (e.g., species richness), our understanding of how seasonality structures other aspects of biodiversity (e.g., functional diversity) has lagged. Integrating seasonal species distributions with comprehensive data on key morphological traits for bird assemblages across North America, we find that seasonal turnover in functional diversity increases with the magnitude and predictability of seasonality. Furthermore, seasonal increases in bird species richness led to a denser packing of functional trait space, but functional expansion was important, especially in regions with higher seasonality. Our results suggest that the magnitude and predictability of seasonality and total productivity can explain the geography of changes in functional diversity with broader implications for understanding species redistribution, community assembly and ecosystem functioning.

Trehalose mediates salinity-stress tolerance in natural populations of a freshwater crustacean

Salinization poses an increasing problem worldwide, threatening freshwater organisms and raising questions about their ability to adapt. We explored the mechanisms enabling a planktonic crustacean to tolerate elevated salinity. By gradually raising water salinity in clonal cultures from 185 Daphnia magna populations, we showed that salt tolerance strongly correlates with native habitat salinity, indicating local adaptation. A genome-wide association study (GWAS) further revealed a major effect of the Alpha,alpha-trehalose-phosphate synthase (TPS) gene, suggesting that trehalose production facilitates salinity tolerance. Salinity-tolerant animals showed a positive correlation between water salinity and trehalose concentrations, while intolerant animals failed to produce trehalose. Animals with a non-functional TPS gene, generated through CRISPR-Cas9, supported the trehalose role in salinity stress. Our study highlights how a keystone freshwater animal adapts to salinity stress using an evolutionary mechanism known in bacteria, plants, and arthropods.

Invasive shrubs differentially alter autumnal activity for three common small-mammal species

Seasonal variation in animal activity influences fitness and the intensity of ecological interactions (e.g., competition, predation), yet aspects of global change in the Anthropocene may catalyze shifts in seasonal activity. Invasive plants are components of global change and can modify animal daily activity, but their influence on animal seasonal activity is less understood. We examined how invasive woody shrubs (Autumn olive [Elaeagnus umbellata] and Amur honeysuckle [Lonicera maackii]) affect seasonal activity of three common small-mammal species by coupling experimental shrub removal with autumnal camera trapping for two consecutive years at six paired forest sites (total 12 plots). Eastern chipmunks (Tamias striatus) foraged more, and foraging was observed at least 20 days longer, in shrub-invaded forests. White-footed mice (Peromyscus leucopus) foraged more in invaded than cleared plots in one study year, but P. leucopus autumn activity timing did not differ between shrub-removal treatments. Fox squirrel (Sciurus niger) activity displayed year-specific responses to shrub removal suggesting intraannual cues (e.g., temperature) structure S. niger autumnal activity. Our work highlights how plant invasions can have species-specific effects on seasonal animal activity, may modify the timing of physiological processes (e.g., torpor), and could generate variation in animal-mediated interactions such as seed dispersal or granivory.

Feeding en route: Prey availability and traits influence prey selection by an avian predator on migration

During animal migration, ephemeral communities of taxa at all trophic levels co-occur over space and time. The interactions between predators and prey along migration corridors are ecologically and evolutionarily significant. However, these interactions remain understudied in terrestrial systems and warrant further investigations using novel approaches. We investigated the predator-prey interactions between a migrating avivorous predator and ephemeral avian prey community in the fall migration season. We tested for associations between avian traits and prey selection and hypothesized that prey traits (i.e. relative size, flocking behaviour, habitat, migration tendency and availability) would influence prey selection by a sexually dimorphic raptor on migration. To document prey consumption, we sampled trace prey DNA from beaks and talons of migrating sharp-shinned hawks Accipiter striatus (n = 588). We determined prey availability in the ephemeral avian community by extracting weekly abundance indices from eBird Status and Trends data. We used discrete choice models to assess prey selection and visualized the frequency of prey in diet and availability on the landscape over the fall migration season. Using eDNA metabarcoding, we detected prey species on 94.1% of the hawks sampled (n = 525/588) comprising 1396 prey species detections from 65 prey species. Prey frequency in diet and eBird relative abundance of prey species were correlated over the migration season for top-selected prey species, suggesting prey availability is an important component of raptor-songbird interactions during fall. Prey size, flocking behaviour and non-breeding habitat association were prey traits that significantly influenced predator choice. We found differences between female and male hawk prey selection, suggesting that sexual size dimorphism has led to distinct foraging strategies on migration. This research integrated field data collected by a volunteer-powered raptor migration monitoring station and public-generated data from eBird to reveal elusive predator-prey dynamics occurring in an ephemeral raptor-songbird community during fall migration. Understanding dynamic raptor-songbird interactions along migration routes remains a relatively unexplored frontier in animal ecology and is necessary for the conservation and management efforts of migratory and resident communities.

Agreements for conserving migratory shorebirds in the Asia-Pacific are better fit for addressing habitat loss than hunting

A full-life cycle approach is a tenet of migratory species conservation, yet the degree to which this is achieved remains largely unassessed. This knowledge gap can be addressed using the concept of social-ecological fit, understood as the match between governance and ecological dimensions. Here, we assess the social-ecological fit for conserving migratory shorebirds in the Asia-Pacific, focusing on habitat loss and hunting. We identify the governance architectures for addressing these two threats and then assess the coordinating capacity of each architecture, measure institutional coverage for each species across their range, and determine the degree of institutional connectivity along their migratory network. We find that social-ecological fit is higher for the governance of habitat designation than for hunting management, with implications for governance practice. Analyses of social-ecological fit thus provide critical insights on the potential effectiveness of governance and therefore are a useful first step for migratory species conservation.

Migratory-derived resources induce elongated food chains through middle-up food web effects

BACKGROUND

Seasonal movements of animals often result in the transfer of large amounts of energy and nutrients across ecosystem boundaries, which may have large consequences on local food webs through various pathways. While this is known for both terrestrial- and aquatic organisms, quantitative estimates on its effects on food web structure and identification of key pathways are scarce, due to the difficulty in obtaining replication on ecosystem level with negative control, i.e. comparable systems without migration.

METHODS

In this study, we estimate the impact of Arctic charr (Salvelinus alpinus) migration on riverine ecosystem structure, by comparing multiple streams with strictly resident populations above natural migration barriers with streams below those barriers harboring partially migratory populations. We compared density estimates and size structure between above and below populations. Diet differences were examined through the analysis of stomach contents, changes in trophic position were examined by using stable isotopes. To infer growth rate of resident individuals, back-growth calculation was performed using otoliths.

RESULTS

We find higher densities of small juveniles in partially migratory populations, where juvenile Arctic charr show initially lower growth, likely due to higher intraspecific competition. After reaching a size, where they can start feeding on eggs and smaller juveniles, which are both more frequent in partially migratory populations, growth surpasses that of resident populations. Cannibalism induced by high juvenile densities occurred almost exclusively in populations with migration and represents an altered energy pathway to the food web. The presence of large cannibalistic charr feeding on smaller ones that have a similar trophic level as charr from strictly resident populations (based on stomach content) coupled with steeper δ15N-size regression slopes illustrate the general increase of food chain length in systems with migration.

CONCLUSIONS

Our results thus suggest that the consumption of migration-derived resources may result in longer food chains through middle-up rather than bottom-up effects. Furthermore, by occupying the apex of the food chain and feeding on juvenile conspecifics, resident individuals experience reduced competition with their young counterparts, which potentially balances their fitness with migratory individuals.

Persistent species relationships characterize migrating bird communities across stopover sites and seasons

Global migrations of diverse animal species often converge along the same routes, bringing together seasonal assemblages of animals that may compete, prey on each other, and share information or pathogens. These interspecific interactions, when energetic demands are high and the time to complete journeys is short, may influence survival, migratory success, stopover ecology, and migratory routes. Numerous accounts suggest that interspecific co-migrations are globally distributed in aerial, aquatic, and terrestrial systems, although the study of migration to date has rarely investigated species interactions among migrating animals. Here, we test the hypothesis that migrating animals are communities engaged in networks of ecological interactions. We leverage over half a million records of 50 bird species from five bird banding sites collected over 8 to 23 y to test for species associations using social network analyses. We find strong support for persistent species relationships across sites and between spring and fall migration. These relationships may be ecologically meaningful: They are often stronger among phylogenetically related species with similar foraging behaviors and nonbreeding ranges even after accounting for the nonsocial contributions to associations, including overlap in migration timing and habitat use. While interspecific interactions could result in costly competition or beneficial information exchange, we find that relationships are largely positive, suggesting limited competitive exclusion at the scale of a banding station during migratory stopovers. Our findings support an understanding of animal migrations that consist of networked communities rather than random assemblages of independently migrating species, encouraging future studies of the nature and consequences of co-migrant interactions.

Networking nutrients: How nutrition determines the structure of ecological networks

Nutrients can shape ecological interactions but remain poorly integrated into ecological networks. Concepts such as nutrient-specific foraging nevertheless have the potential to expose the mechanisms structuring complex ecological systems. Nutrients also present an opportunity to predict dynamic processes, such as interaction rewiring and extinction cascades, and increase the accuracy of network analyses. Here, we propose the concept of nutritional networks. By integrating nutritional data into ecological networks, we envisage significant advances to our understanding of ecological processes from individual to ecosystem scales. We show that networks can be constructed with nutritional data to illuminate how nutrients structure ecological interactions in natural systems through an empirical example. Throughout, we identify fundamental ecological hypotheses that can be explored in a nutritional network context, alongside methods for resolving those networks. Nutrients influence the structure and complexity of ecological networks through mechanistic processes and concepts including nutritional niche differentiation, functional responses, landscape diversity, ecological invasions and ecosystem robustness. Future research on ecological networks should consider nutrients when investigating the drivers of network structure and function.

Elucidating nematode diversity and prevalence in moose across a wide latitudinal gradient using DNA metabarcoding

Parasitic nematodes are ubiquitous and can negatively impact their host by reducing fecundity or increasing mortality, yet the driver of variation in the parasite community across a wildlife host's geographic distribution remains elusive for most species. Based on an extensive collection of fecal samples (n = 264) from GPS marked moose (Alces alces), we used DNA metabarcoding to characterize the individual (sex, age class) and seasonal parasitic nematode community in relation to habitat use and migration behavior in five populations distributed across a wide latitudinal gradient (59.6°N to 70.5°N) in Norway. We detected 21 distinct nematode taxa with the six most common being Ostertagia spp., Nematodirella spp., Trichostongylus spp., T. axei, Elaphostrongylus alces, and an unclassified Strongylida. There was higher prevalence of livestock parasites in areas with larger sheep populations indicating a higher risk of spillover events. The individual level nematode richness was mostly consistent across study areas, while the number and type of nematode taxa detected at each study area varied considerably but did not follow a latitudinal gradient. While migration distance affected nematode beta-diversity across all sites, it had a positive effect on richness at only two of the five study areas suggesting population specific effects. Unexpectedly, nematode richness was higher in winter than summer when very few nematodes were detected. Here we provide the first extensive description of the parasitic nematode community of moose across a wide latitudinal range. Overall, the population-specific impact of migration on parasitism across the distribution range and variation in sympatry with other ruminants suggest local characteristics affect host-parasite relationships.

Animal migration in the Anthropocene: threats and mitigation options

Animal migration has fascinated scientists and the public alike for centuries, yet migratory animals are facing diverse threats that could lead to their demise. The Anthropocene is characterised by the reality that humans are the dominant force on Earth, having manifold negative effects on biodiversity and ecosystem function. Considerable research focus has been given to assessing anthropogenic impacts on the numerical abundance of species/populations, whereas relatively less attention has been devoted to animal migration. However, there are clear linkages, for example, where human-driven impacts on migration behaviour can lead to population/species declines or even extinction. Here, we explore anthropogenic threats to migratory animals (in all domains - aquatic, terrestrial, and aerial) using International Union for the Conservation of Nature (IUCN) Threat Taxonomy classifications. We reveal the diverse threats (e.g. human development, disease, invasive species, climate change, exploitation, pollution) that impact migratory wildlife in varied ways spanning taxa, life stages and type of impact (e.g. from direct mortality to changes in behaviour, health, and physiology). Notably, these threats often interact in complex and unpredictable ways to the detriment of wildlife, further complicating management. Fortunately, we are beginning to identify strategies for conserving and managing migratory animals in the Anthropocene. We provide a set of strategies that, if embraced, have the potential to ensure that migratory animals, and the important ecological functions sustained by migration, persist.

Does host migration affect host-parasite interaction? Migrant birds harbor exclusive parasites but have similar roles in parasite-host networks

Parasites comprise a substantial portion of global biodiversity and play critical roles in shaping ecosystems by modulating trophic networks and affecting their hosts' abundance and distribution. The dynamics of host migration introduce new complexity to these relationships. From the host perspective, migratory behavior can either act as a defense mechanism or augment exposure to a broader spectrum of pathogens. Conversely, for parasites, host migration represents a mechanism for their dispersion and an opportunity to infect new host species. This study investigates the complex interplay between migration and parasite-host interactions, focusing on the interaction between hosts and avian malaria and malaria-like parasites in the Brazilian Atlantic Rain Forest. We captured 1466 birds representing 70 different species, uncovering 322 infections with Plasmodium/Haemoproteus parasites. We observed variations in migration timing and fluctuations in host abundance across months. By comparing the observed patterns of interaction of migratory and non-migratory birds to patterns of interaction expected at random, we show that migration affects the roles hosts take in the parasite-host network. Interestingly, despite the fact migratory species hosted more exclusive and distinct parasites, migrants did not occupy central network positions, which are mostly occupied by resident birds. Overall, we highlight the role of resident birds as a key species within parasite-host communities and the high specialization among avian haemosporidians and their hosts.

Seabird transported contaminants are dispersed in island ecosystems

Seabirds are long-range transporters of nutrients and contaminants, linking marine feeding areas with terrestrial breeding and roosting sites. By depositing nutrient-rich guano, which acts as a fertiliser, seabirds can substantially influence the terrestrial environment in which they reside. However, increasing pollution of the marine environment has resulted in guano becoming similarly polluted. Here, we determined metal and metalloid concentrations (As, Cd, Cr, Cu, Hg, Pb) in Flesh-footed Shearwater (Ardenna carneipes) guano, soil, terrestrial flora, and primary consumers and used an ecological approach to assess whether the trace elements in guano were bioaccumulating and contaminating the surrounding environment. Concentrations in guano were higher than those of other Procellariiformes documented in the literature, which may be influenced by the high amounts of plastics that this species of shearwater ingests. Soil samples from shearwater colonies had significantly higher concentrations of all metals, except for Pb, than soils from control sites and formerly occupied areas. Concentrations in terrestrial primary producers and primary consumers were not as marked, and for many contaminants there was no significant difference observed across levels of ornithogenic input. We conclude that Flesh-footed Shearwaters are transporters of marine derived contaminants to the Lord Howe Island terrestrial environment.

Effects of migratory animals on resident parasite dynamics

Migratory animals can bring parasites into resident animal (i.e., non-migratory) home ranges (transport effects) and exert trophic effects that either promote or reduce parasite exposure to resident hosts. Here, we examine the importance of these transport and trophic effects and their interactions for resident parasite dynamics. We propose that migrant transport and trophic effects are impacted by the number of migratory animals entering a resident's home range (migration intensity), the amount of time that migrants spend within a resident's home range (migration duration), and the timing of migrant-resident interactions. We then incorporate migration intensity, duration, and timing into a framework for exploring the net impact of migrant trophic and transport effects on resident animal parasite prevalence.

Effects of nocturnal celestial illumination on high-flying migrant insects

Radar networks hold great promise for monitoring population trends of migrating insects. However, it is important to elucidate the nature of responses to environmental cues. We use data from a mini-network of vertical-looking entomological radars in the southern UK to investigate changes in nightly abundance, flight altitude and behaviour of insect migrants, in relation to meteorological and celestial conditions. Abundance of migrants showed positive relationships with air temperature, indicating that this is the single most important variable influencing the decision to initiate migration. In addition, there was a small but significant effect of moonlight illumination, with more insects migrating on full moon nights. While the effect of nocturnal illumination levels on abundance was relatively minor, there was a stronger effect on the insects' ability to orientate close to downwind: flight headings were more tightly clustered on nights when the moon was bright and when cloud cover was sparse. This indicates that nocturnal illumination is important for the navigational mechanisms used by nocturnal insect migrants. Further, our results clearly show that environmental conditions such as air temperature and light levels must be considered if long-term radar datasets are to be used to assess changing population trends of migrants. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.

Monitoring aerial insect biodiversity: a radar perspective

In the current biodiversity crisis, populations of many species have alarmingly declined, and insects are no exception to this general trend. Biodiversity monitoring has become an essential asset to detect biodiversity change but remains patchy and challenging for organisms that are small, inconspicuous or make (nocturnal) long-distance movements. Radars are powerful remote-sensing tools that can provide detailed information on intensity, timing, altitude and spatial scale of aerial movements and might therefore be particularly suited for monitoring aerial insects and their movements. Importantly, they can contribute to several essential biodiversity variables (EBVs) within a harmonized observation system. We review existing research using small-scale biological and weather surveillance radars for insect monitoring and outline how the derived measures and quantities can contribute to the EBVs 'species population', 'species traits', 'community composition' and 'ecosystem function'. Furthermore, we synthesize how ongoing and future methodological, analytical and technological advancements will greatly expand the use of radar for insect biodiversity monitoring and beyond. Owing to their long-term and regional-to-large-scale deployment, radar-based approaches can be a powerful asset in the biodiversity monitoring toolbox whose potential has yet to be fully tapped. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.

Continental-scale patterns in diel flight timing of high-altitude migratory insects

Many insects depend on high-altitude, migratory movements during part of their life cycle. The daily timing of these migratory movements is not random, e.g. many insect species show peak migratory flight activity at dawn, noon or dusk. These insects provide essential ecosystem services such as pollination but also contribute to crop damage. Quantifying the diel timing of their migratory flight and its geographical and seasonal variation, are hence key towards effective conservation and pest management. Vertical-looking radars provide continuous and automated measurements of insect migration, but large-scale application has not been possible because of limited availability of suitable devices. Here, we quantify patterns in diel flight periodicity of migratory insects between 50 and 500 m above ground level during March-October 2021 using a network of 17 vertical-looking radars across Europe. Independent of the overall daily migratory movements and location, peak migratory movements occur around noon, during crepuscular evening and occasionally the morning. Relative daily proportions of insect migration intensity and traffic during the diel phases of crepuscular-morning, day, crepuscular-evening and night remain largely equal throughout May-September and across Europe. These findings highlight, extend, and generalize previous regional-scale findings on diel migratory insect movement patterns to the whole of temperate Europe. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.

Invasive species drive cross-ecosystem effects worldwide

Invasive species are pervasive around the world and have profound impacts on the ecosystem they invade. Invasive species, however, can also have impacts beyond the ecosystem they invade by altering the flow of non-living materials (for example, nutrients or chemicals) or movement of organisms across the boundaries of the invaded ecosystem. Cross-ecosystem interactions via spatial flows are ubiquitous in nature, for example, connecting forests and lakes, grasslands and rivers, and coral reefs and the deep ocean. Yet, we have a limited understanding of the cross-ecosystem impacts invasive species have relative to their local effects. By synthesizing emerging evidence, here we demonstrate the cross-ecosystem impacts of invasive species as a ubiquitous phenomenon that influences biodiversity and ecosystem functioning around the world. We identify three primary ways by which invasive species have cross-ecosystem effects: first, by altering the magnitude of spatial flows across ecosystem boundaries; second, by altering the quality of spatial flows; and third, by introducing novel spatial flows. Ultimately, the strong impacts invasive species can drive across ecosystem boundaries suggests the need for a paradigm shift in how we study and manage invasive species around the world, expanding from a local to a cross-ecosystem perspective.

The propagation of disturbances in ecological networks

Despite the development of network science, we lack clear heuristics for how far different disturbance types propagate within and across species interaction networks. We discuss the mechanisms of disturbance propagation in ecological networks, and propose that disturbances can be categorized into structural, functional, and transmission types according to their spread and effect on network structure and functioning. We describe the properties of species and their interaction networks and metanetworks that determine the indirect, spatial, and temporal extent of propagation. We argue that the sampling scale of ecological studies may have impeded predictions regarding the rate and extent that a disturbance spreads, and discuss directions to help ecologists to move towards a predictive understanding of the propagation of impacts across interacting communities and ecosystems.

Farm management and landscape context shape plant diversity at wetland edges in the Prairie Pothole Region of Canada

Evaluating the impacts of farming systems on biodiversity is increasingly important given the need to stem biodiversity loss, decrease fossil fuel dependency, and maintain ecosystem services benefiting farmers. We recorded woody and herbaceous plant species diversity, composition, and abundance in 43 wetland-adjacent prairie remnants beside crop fields managed using conventional, minimum tillage, organic, or perennial cover (wildlife-friendly) land management in the Prairie Pothole Region. We used a hierarchical framework to estimate diversity at regional and local scales (gamma, alpha), and how these are related through species turnover (beta diversity). We tested the expectation that gamma richness/evenness and beta diversity of all plants would be higher in remnants adjacent to perennial cover and organic fields than in conventional and minimum tillage fields. We expected the same findings for plants providing ecosystem services (bee-pollinated species) and disservices (introduced species). We predicted similar relative effects of land management on alpha diversity, but with the expectation that the benefits of organic farming would decrease with increasing grassland in surrounding landscapes. Gamma richness and evenness of all plants were highest for perennial cover, followed by minimum tillage, organic, and conventional sites. Bee-pollinated species followed a similar pattern for richness, but for evenness organic farming came second, after perennial cover sites, followed by minimum tillage and conventional. For introduced species, organic sites had the highest gamma richness and evenness. Grassland amount moderated the effect of land management type on all plants and bee-pollinated plant richness, but not as expected. The richness of organic sites increased with the amount of grassland in the surrounding landscape. Conversely, for conventional sites, richness increased as the amount of grassland in the landscape declined. Our results are consistent with the expectation that adopting wildlife-friendly land management practices can benefit biodiversity at regional and local scales, in particular the use of perennial cover to benefit plant diversity at regional scales. At more local extents, organic farming increased plant richness, but only when sufficient grassland was available in the surrounding landscape; organic farms also had the highest beta diversity for all plants and bee-pollinated plants. Maintaining native cover in agroecosystems, in addition to low-intensity farming practices, could sustain plant biodiversity and facilitate important ecosystem services.

Predicting resilience of migratory birds to environmental change

The pace and scale of environmental change represent major challenges to many organisms. Animals that move long distances, such as migratory birds, are especially vulnerable to change since they need chains of intact habitat along their migratory routes. Estimating the resilience of such species to environmental changes assists in targeting conservation efforts. We developed a migration modeling framework to predict past (1960s), present (2010s), and future (2060s) optimal migration strategies across five shorebird species (Scolopacidae) within the East Asian-Australasian Flyway, which has seen major habitat deterioration and loss over the last century, and compared these predictions to empirical tracks from the present. Our model captured the migration strategies of the five species and identified the changes in migrations needed to respond to habitat deterioration and climate change. Notably, the larger species, with single or few major stopover sites, need to establish new migration routes and strategies, while smaller species can buffer habitat loss by redistributing their stopover areas to novel or less-used sites. Comparing model predictions with empirical tracks also indicates that larger species with the stronger need for adaptations continue to migrate closer to the optimal routes of the past, before habitat deterioration accelerated. Our study not only quantifies the vulnerability of species in the face of global change but also explicitly reveals the extent of adaptations required to sustain their migrations. This modeling framework provides a tool for conservation planning that can accommodate the future needs of migratory species.

Global prevalence and risk factors associated with Toxoplasma gondii infection in wild birds: A systematic review and meta-analysis

A systematic review and meta-analysis were performed to identify the global prevalence and factors associated with Toxoplasma gondii infection in wild birds. Six bibliographic databases (Chinese National Knowledge Infrastructure, VIP Chinese Journal Database, Wanfang Data, PubMed, Web of science and ScienceDirect) were searched from inception to February 2023. The search yielded 1220 records of which 659 articles underwent full-text evaluation, which identified 49 eligible articles and 16,030 wild bird samples that were included in the meta-analysis. The estimated pooled global prevalence of T. gondii infection in wild birds was 16.6%. Out of the variables tested, publication year after 2020 and climate type were significantly associated with T. gondii infection (P<0.01). Our data indicate that the prevalence of T. gondii in wild birds can be influenced by epidemiological variables. Further research is needed to identify the biological, environmental, anthropogenic, and geographical risk factors which impact the ecology and prevalence of T. gondii in wild birds.

Massive seasonal high-altitude migrations of nocturnal insects above the agricultural plains of East China

Long-distance migrations of insects contribute to ecosystem functioning but also have important economic impacts when the migrants are pests or provide ecosystem services. We combined radar monitoring, aerial sampling, and searchlight trapping, to quantify the annual pattern of nocturnal insect migration above the densely populated agricultural lands of East China. A total of ~9.3 trillion nocturnal insect migrants (15,000 t of biomass), predominantly Lepidoptera, Hemiptera, and Diptera, including many crop pests and disease vectors, fly at heights up to 1 km above this 600 km-wide region every year. Larger migrants (>10 mg) exhibited seasonal reversal of movement directions, comprising northward expansion during spring and summer, followed by southward movements during fall. This north-south transfer was not balanced, however, with southward movement in fall 0.66× that of northward movement in spring and summer. Spring and summer migrations were strongest when the wind had a northward component, while in fall, stronger movements occurred on winds that allowed movement with a southward component; heading directions of larger insects were generally close to the track direction. These findings indicate adaptations leading to movement in seasonally favorable directions. We compare our results from China with similar studies in Europe and North America and conclude that ecological patterns and behavioral adaptations are similar across the Northern Hemisphere. The predominance of pests among these nocturnal migrants has severe implications for food security and grower prosperity throughout this heavily populated region, and knowledge of their migrations is potentially valuable for forecasting pest impacts and planning timely management actions.

Crop cover and nutrient levels mediate the effects of land management type on aquatic invertebrate richness in prairie potholes

Aquatic invertebrates provide important ecosystem services, including decomposition and nutrient cycling, and provide nutrition for birds, fish, amphibians, and bats. Thus, the effects of agricultural land management practices on aquatic invertebrates are relevant to farmers, wildlife biologists, and policymakers. Here, we used data on aquatic invertebrates (159 taxa, 73 to species, 75 to genus/family) collected in 40 wetlands in the Canadian prairies to test for direct and indirect relationships among land management types (perennial cover, organic, minimum tillage, conventional), landscape structure (cropland and wetland cover within the surrounding landscape), and water quality (total nutrient levels, turbidity) on species richness of invertebrates using structural equation modelling. Additionally, we assessed variation in community composition within and among wetlands in different land use management types using a direct gradient analysis and variance partitioning. The direct effects of land management type were not supported but we found strong supportive evidence that effects of land management on richness were significantly mediated through cropland cover, nutrient levels, and turbidity. After controlling for these indirect effects, aquatic invertebrate richness decreased along a gradient from the lowest to the highest farming intensity, i.e., richness decreased from perennial cover sites to organic to minimum tillage to conventional sites. Support was also found for negative effects of nutrient levels and turbidity on richness. We did not find significant support for differences in gamma diversity or a simple test (homogeneity of multivariate dispersions) of differences in turnover among land management types; however, land management had a significant effect in distance-based redundancy analysis. Taken together, these results suggest that focusing conservation efforts on reducing cropland erosion and nutrient inputs to wetlands and creating more permanent cover may be effective strategies for conserving richness of aquatic invertebrates in agricultural landscapes in this region.

Existing evidence on the effects of climate variability and climate change on ungulates in North America: a systematic map

BACKGROUND

Climate is an important driver of ungulate life-histories, population dynamics, and migratory behaviors. Climate conditions can directly impact ungulates via changes in the costs of thermoregulation and locomotion, or indirectly, via changes in habitat and forage availability, predation, and species interactions. Many studies have documented the effects of climate variability and climate change on North America's ungulates, recording impacts to population demographics, physiology, foraging behavior, migratory patterns, and more. However, ungulate responses are not uniform and vary by species and geography. Here, we present a systematic map describing the abundance and distribution of evidence on the effects of climate variability and climate change on native ungulates in North America.

METHODS

We searched for all evidence documenting or projecting how climate variability and climate change affect the 15 ungulate species native to the U.S., Canada, Mexico, and Greenland. We searched Web of Science, Scopus, and the websites of 62 wildlife management agencies to identify relevant academic and grey literature. We screened English-language documents for inclusion at both the title and abstract and full-text levels. Data from all articles that passed full-text review were extracted and coded in a database. We identified knowledge clusters and gaps related to the species, locations, climate variables, and outcome variables measured in the literature.

REVIEW FINDINGS

We identified a total of 674 relevant articles published from 1947 until September 2020. Caribou (Rangifer tarandus), elk (Cervus canadensis), and white-tailed deer (Odocoileus virginianus) were the most frequently studied species. Geographically, more research has been conducted in the western U.S. and western Canada, though a notable concentration of research is also located in the Great Lakes region. Nearly 75% more articles examined the effects of precipitation on ungulates compared to temperature, with variables related to snow being the most commonly measured climate variables. Most studies examined the effects of climate on ungulate population demographics, habitat and forage, and physiology and condition, with far fewer examining the effects on disturbances, migratory behavior, and seasonal range and corridor habitat.

CONCLUSIONS

The effects of climate change, and its interactions with stressors such as land-use change, predation, and disease, is of increasing concern to wildlife managers. With its broad scope, this systematic map can help ungulate managers identify relevant climate impacts and prepare for future changes to the populations they manage. Decisions regarding population control measures, supplemental feeding, translocation, and the application of habitat treatments are just some of the management decisions that can be informed by an improved understanding of climate impacts. This systematic map also identified several gaps in the literature that would benefit from additional research, including climate effects on ungulate migratory patterns, on species that are relatively understudied yet known to be sensitive to changes in climate, such as pronghorn (Antilocapra americana) and mountain goats (Oreamnos americanus), and on ungulates in the eastern U.S. and Mexico.

Learning shapes the development of migratory behavior

How animals refine migratory behavior over their lifetime (i.e., the ontogeny of migration) is an enduring question with important implications for predicting the adaptive capacity of migrants in a changing world. Yet, our inability to monitor the movements of individuals from early life onward has limited our understanding of the ontogeny of migration. The exploration-refinement hypothesis posits that learning shapes the ontogeny of migration in long-lived species, resulting in greater exploratory behavior early in life followed by more rapid and direct movement during later life. We test the exploration-refinement hypothesis by examining how white storks (Ciconia ciconia) balance energy, time, and information as they develop and refine migratory behavior during the first years of life. Here, we show that young birds reduce energy expenditure during flight while also increasing information gain by exploring new places during migration. As the birds age and gain more experience, older individuals stop exploring new places and instead move more quickly and directly, resulting in greater energy expenditure during migratory flight. During spring migration, individuals innovated novel shortcuts during the transition from early life into adulthood, suggesting a reliance on spatial memory acquired through learning. These incremental refinements in migratory behavior provide support for the importance of individual learning within a lifetime in the ontogeny of long-distance migration.

Vicuña antipredator diel movement drives spatial nutrient subsidies in a high Andean ecosystem

Large animals could be important drivers of spatial nutrient subsidies when they ingest resources in some habitats and release them in others, even moving nutrients against elevational gradients. In high Andean deserts, vicuñas (Vicugna vicugna) move daily between nutrient-rich wet meadows, where there is abundant water and forage but high risk of predation by pumas (Puma concolor), and nutrient-poor open plains with lower risk of predation. In all habitats, vicuñas defecate and urinate in communal latrines. We investigated how these latrines impacted soil and plant nutrient concentrations across three habitats in the Andean ecosystem (meadows, plains, and canyons) and used stable isotope analysis to explore the source of fecal nutrients in latrines. Latrine soils had higher concentrations of nitrogen, carbon, and other nutrients than did nonlatrine soils across all habitats. These inputs corresponded with an increase in plant quality (lower C:N) at latrine sites in plains and canyons, but not in meadows. Stable isotope mixing models suggest that ~7% of nutrients in plains latrines originated from vegetation in meadows, which is disproportionately higher than the relative proportion of meadow habitat (2.6%) in the study area. In contrast, ~68% of nutrients in meadow latrines appear to originate from plains and canyon vegetation, though these habitats made up nearly 98% of the study area. Vicuña diel movements thus appear to concentrate nutrients in latrines within habitats and to drive cross-habitat nutrient subsidies, with disproportionate transport from low-lying, nutrient-rich meadows to more elevated, nutrient-poor plains. When these results are scaled up to the landscape scale, the amount of nitrogen and phosphorus subsidized in soil at plains latrines was of the same order of magnitude as estimates of annual atmospheric nitrogen and phosphorus deposition for this region (albeit far more localized and patchy). Thus, vicuña-mediated nutrient redistribution and deposition appears to be an important process impacting ecosystem functioning in arid Andean environments, on par with other major inputs of nutrients to the system.