Seasonal Bird Migration Research Articles

Migratory lifestyle carries no added overall energy cost in a partial migratory songbird.

Seasonal bird migration may provide energy benefits associated with moving to areas with less physiologically challenging climates or increased food availability, but migratory movements themselves may carry high costs. However, time-dynamic energy profiles of free-living migrants-especially small-bodied songbirds-are challenging to measure. Here we quantify energy output and thermoregulatory costs in partially migratory common blackbirds using implanted heart rate and temperature loggers paired with automated radio telemetry and energetic modelling. Our results show that blackbirds save considerable energy in preparation for migration by decreasing heart rate and body temperature 28 days before departure, potentially dwarfing the energy costs of migratory flights. Yet, in warmer wintering areas, migrants do not appear to decrease total daily energy expenditure despite a substantially reduced cost of thermoregulation. These findings indicate differential metabolic programmes across different wintering strategies despite equivalent overall energy expenditure, suggesting that the maintenance of migration is associated with differences in energy allocation rather than with total energy expenditure.

Nocturnal avian migration drives high daily turnover but limited change in abundance on the ground

Every night during spring and autumn, the mass movement of migratory birds redistributes bird abundances found on the ground during the day. However, the connection between the magnitude of nocturnal migration and the resulting change in diurnal abundance remains poorly quantified. If departures and landings at the same location are balanced throughout the night, we expect high bird turnover but little change in diurnal abundance (stream‐like migration). Alternatively, migrants may move simultaneously in spatial pulses, with well‐separated areas of departure and landing that cause significant changes in the abundance of birds on the ground during the day (wave‐like migration). Here, we apply a flow model to data from weather surveillance radars (WSR) to quantify the daily fluxes of nocturnally migrating birds landing and departing from the ground, characterizing the movement and stopover of birds in a comprehensive synoptic scale framework. We corroborate our results with independent observations of the diurnal abundances of birds on the ground from eBird. Furthermore, we estimate the abundance turnover, defined as the proportion of birds replaced overnight. We find that seasonal bird migration chiefly resembles a stream where bird populations on the ground are continuously replaced by new individuals. Large areas show similar magnitudes of take‐off and landing, coupled with relatively small distances flown by birds each night, resulting in little change in bird densities on the ground. We further show that WSR‐inferred landing and take‐off fluxes predict changes in eBird‐derived abundance turnover rate and turnover in species composition. We find that the daily turnover rate of birds is 13% on average but can reach up to 50% on peak migration nights. Our results highlight that WSR networks can provide real‐time information on rapidly changing bird distributions on the ground. The flow model applied to WSR data can be a valuable tool for real‐time conservation and public engagement focused on migratory birds' daytime stopovers.

Synchrony of Bird Migration with Global Dispersal of Avian Influenza Reveals Exposed Bird Orders

Highly pathogenic avian influenza virus (HPAIV) A H5, particularly clade 2.3.4.4, has caused worldwide outbreaks in domestic poultry, occasional spillover to humans, and increasing deaths of diverse species of wild birds since 2014. Wild bird migration is currently acknowledged as an important ecological process contributing to the global dispersal of HPAIV H5. However, this mechanism has not been quantified using bird movement data from different species, and the timing and location of exposure of different species is unclear. We sought to explore these questions through phylodynamic analyses based on empirical data of bird movement tracking and virus genome sequences of clade 2.3.4.4 and 2.3.2.1. First, we demonstrate that seasonal bird migration can explain salient features of the global dispersal of clade 2.3.4.4. Second, we detect synchrony between the seasonality of bird annual cycle phases and virus lineage movements. We reveal the differing exposed bird orders at geographical origins and destinations of HPAIV H5 clade 2.3.4.4 lineage movements, including relatively under-discussed orders. Our study provides a phylodynamic framework that links the bird movement ecology and genomic epidemiology of avian influenza; it highlights the importance of integrating bird behavior and life history in avian influenza studies.

Birds of a feather flock together: a dataset for Clock and Adcyap1 genes from migration genetics studies

Birds in seasonal habitats rely on intricate strategies for optimal timing of migrations. This is governed by environmental cues, including photoperiod. Genetic factors affecting intrinsic timekeeping mechanisms, such as circadian clock genes, have been explored, yielding inconsistent findings with potential lineage-dependency. To clarify this evidence, a systematic review and phylogenetic reanalysis was done. This descriptor outlines the methodology for sourcing, screening, and processing relevant literature and data. PRISMA guidelines were followed, ultimately including 66 studies, with 34 focusing on candidate genes at the genotype-phenotype interface. Studies were clustered using bibliographic coupling and citation network analysis, alongside scientometric analyses by publication year and location. Data was retrieved for allele data from databases, article supplements, and direct author communications. The dataset, version 1.0.2, encompasses data from 52 species, with 46 species for the Clock gene and 43 for the Adcyap1 gene. This dataset, featuring data from over 8000 birds, constitutes the most extensive cross-species collection for these candidate genes, used in studies investigating gene polymorphisms and seasonal bird migration.

Decoupled spatiotemporal patterns of avian taxonomic and functional diversity

Each year, seasonal bird migration leads to an immense redistribution of species occurrence and abundances,1,2,3 with pervasive, though unclear, consequences for patterns of multi-faceted avian diversity. Here, we uncover stark disparities in spatiotemporal variation between avian taxonomic diversity (TD) and functional diversity (FD) across the continental US. We show that the seasonality of species richness expectedly3 follows a latitudinal gradient, whereas seasonality of FD instead manifests a distinct east-west gradient. In the eastern US, the temporal patterns of TD and FD are diametrically opposed. In winter, functional richness is highest despite seasonal species loss, and the remaining most abundant species are amassed in fewer regions of the functional space relative to the rest of the year, likely reflecting decreased resource availability. In contrast, temporal signatures for TD and FD are more congruent in the western US. There, both species and functional richness peak during the breeding season, and species' abundances are more regularly distributed and widely spread across the functional space than during winter. Our results suggest that migratory birds in the western US disproportionately contribute to avian FD by possessing more unique trait characteristics than resident birds,4,5 while the primary contribution of migrants in the eastern US is through increasing the regularity of abundances within the functional space relative to the rest of the year. We anticipate that the uncovered complexity of spatiotemporal associations among measures of avian diversity will be the catalyst for adopting an explicitly temporal framework for multi-faceted biodiversity analysis.

Capabilities of the WEBBIRDS system in the process of assessing the impact of wind farms on seasonal bird complexes on the example of spring migrants at the Botiieve wind farm in 2013-2021

This paper contains the analyzed results of field observations of the spring migration of birds on the territory of the Botiieve wind farm in 2013-2021. The work was carried out as part of the planned monitoring of the ornithological situation in the area of the Botiieve wind farm (Pryazovskyi district, Zaporizhzhia region) and also covered the Tubal Estuary formed by the confluence of the Velyka and Mala Domuzla and Akchokrak Rivers and in the mouth of the Korsak River. During each trip, up to 70% of the wind farm area was covered. There were given characteristics of the taxonomic composition of the ornithocomplex, flight phenology, height and direction of migration by seasons and months. In the spring period of 2013-2021, 156,910 individuals of 125 species were recorded in the project area. 52,575 individuals of 92 species of these birds (33.5%) were observed directly within the Botiieve wind farm and buffer zones and there were recorded 104,335 individuals of 99 species (66.5%) at the adjacent wetlands - the Botiieve Ponds and the Tubal Estuary. New methods for collecting, storing and processing information, including mapping, server storage and data processing using two web applications, have been proposed. In order to describe in detail the migration processes in the local area, methods of vector mathematics, as well as computer vision algorithms, were used. The result of the analysis was a gradient map of seasonal bird migration concentration, which allows a differentiated approach to assessing the threats to birds from operating wind turbines. The impact of the Botiieve wind farm on birds during the period of seasonal migrations is estimated to be low.

Phenological synchronization of seasonal bird migration with vegetation greenness across dietary guilds.

The seasonal movement of animals has been linked to seasonal variation in ecological productivity, and it has been hypothesized that primary consumers synchronize migration with vegetation phenology. Within temperate regions of the Northern Hemisphere, herbivorous bird species often track the phenology of vegetation greenness during spring migration. Phenological synchronization with vegetation greenness by migratory birds in other dietary guilds, across the full extent of their annual distributions during both spring and autumn migration, has not been explored. Here, we document population-level associations with a remotely sensed measure of vegetation greenness for 230 North American migratory bird species in seven dietary guilds across the full annual cycle using eBird occurrence information for the combined period 2006-2018. Evidence of phenological synchronization was strongest for omnivores, herbivores, herbivore-granivores and granivores during spring and autumn migration, except for omnivores in the west during spring migration. Strong evidence of synchronization was also observed for insectivores during spring migration and carnivores during spring and autumn migration that migrated across the entire breadth of the continent. The level of evidence declined for insectivores in the west and east during spring migration, and for nectarivores in the west during spring and autumn migration. Limited evidence was also found for insectivores in the east during autumn migration, insectivores in the west and the centre of the continent during spring and autumn migration, and carnivores in the west during spring migration. Carnivores in the west during autumn migration showed the weakest evidence of synchronization. We found broad support across an array of dietary guilds for phenological coupling between vegetation greenness and seasonal bird migration within North America. Our results highlight the potential for many migratory bird species to encounter phenological mismatches as vegetation phenology responds to climate change. Our findings emphasize the need to better understand the environmental cues that regulate migratory behaviour across dietary guilds, consumer levels and migration tactics.

Should I stay or should I go?

Migration The global upheaval of seasonal bird migration is an astonishing phenomenon. The European blackcap is a species of small songbird that shows great variation in wanderlust. Delmore et al. collected DNA-sequencing data from blackcaps across their breeding range to determine the genetic basis for variations in migratory behavior. The impulse to migrate and the distance and direction of travel are encoded in small genomic regions. Polymorphisms were found in genes for transcription factors such as Clock, Npas2, and Bma1, which are associated with circadian rhythm. A few genes linked to traits as varied as hyperphagia and fat deposition, learning and memory, and wing length also appear to be under strong selection to rapidly evolve new behaviors. The suite of blackcap migratory genes is distinctive, and it appears that there are many ways to genetically program migration in birds. eLife 9 , e54462 (2020).

Towards the Acoustic Monitoring of Birds Migrating at Night

Every year billions of birds migrate between their breeding and wintering areas. As birds are an important indicator in nature conservation, migratory bird studies have been conducted for many decades, mostly by bird-ringing programmes and direct observation. However, most birds migrate at night, and therefore much information about their migration is lost. Novel methods have been developed to overcome this difficulty; including thermal imaging, radar, geolocation techniques, and acoustic recognition of bird calls. Many bird species are detected by their characteristic sounds. This method of identification occurs more often than by direct observation, and therefore recordings are widely used in avian research. The commonly used approach is to record the birds automatically, and to manually study the bird sounds in the recordings afterwards (Furnas and Callas 2015, Frommolt 2017). However, the tagging of recordings is a tedious and time-consuming process that requires expert knowledge, and, as a result, automatic detection of flight calls is in high demand. The first experiments towards this used energy thresholds or template matching (Bardeli et al. 2010, Towsey et al. 2012), and later on the machine and deep learning methods were applied (Stowell et al. 2018). Nevertheless, not many studies have focused specifically on night flight calls (Salamon et al. 2016, Lostanlen et al. 2018). Such acoustic monitoring could complement daytime avian research, especially when the field recording station is close to the bird-ringing station, as it is in our project. In this study, we present the initial results of a long-term bird audio monitoring project using automatic methods for bird detection. Passive acoustic recorders were deployed at a narrow spit between a lake and the Baltic sea in Dąbkowice, West Pomeranian Voivodeship, Poland . We recorded bird calls nightly from sunset till sunrise during the passerine autumn migration for 3 seasons. As a result, we collected over 3000 hours of recordings each season. We annotated a subset of over 50 hours, from different nights with various weather conditions. As avian flight calls are sporadic and short, we created a balanced set for training - recordings were divided into partially overlapping 500-ms clips, and we retained all clips containing calls and created about the same number of clips without bird sounds. Different signal representations were then examined (e.g. mel-spectrograms and multitaper). Afterwards, various convolutional neural networks were checked and their performance was compared using the area under the receiver operating characteristic curve (AUC) measure. Moreover, an initial attempt was made to take advantage of the transfer learning from image classification models. The results obtained by the deep learning methods are promising (AUC exceeding 80%), but higher bird detection accuracy is still needed. For a chosen bird species – Song thrush (Turdus philomelos) – we observed a correlation between calls recorded at night and birds caught in the nets during the day. This fact, as well as the promising results from the detection of calls from long-term recordings, indicate that acoustic monitoring of nocturnal birds has great potential and could be used to supplement the research of the phenomenon of seasonal bird migration.

Meteorological factors affecting the risk of transmission of HPAI in Miyazaki, Japan

Highly pathogenic avian influenza (HPAI) outbreaks engender a severe economic impact on the poultry industry and public health. Migratory waterfowl are considered the natural hosts of HPAI virus, and HPAI...

Hypothalamic and liver transcriptome from two crucial life-history stages in a migratory songbird.

What is the central question of this study? What are the molecular underpinnings of the seasonal adaptation in a latitudinal migratory songbird? What is the main finding and its importance? We found changes in mRNA levels after a photoperiod-induced alteration of seasonal state in a captive long-distance latitudinal avian migrant. The hypothalamus and liver transcriptomes revealed genes involved in the regulatory and functional pathways between non-migratory and migratory states. Our results provide insights into mechanisms underlying homeostasis during seasonal changes that are conserved across most species, including humans. Very little is understood about genetic mechanisms underlying the onset of spring migration in latitudinal avian migrants. To gain insight into the genetic architecture of the hypothalamus and liver tissues of a long-distance migrant, we examined and compared the transcriptome profile of captive night-migratory black-headed buntings (Emberiza melanocephala) between photoperiod-induced winter non-migratory (WnM) and spring migratory (SM) life-history states under short and long days, respectively. High-throughput 454 pyrosequenced transcripts were mapped initially with reference to the genome of two phylogenetically close species, Taeniopygia guttata and Ficedula albicollis. The F. albicollis genome gave higher annotation results and was used for further analysis. A total of 216 (78 in hypothalamus; 138 in liver) genes were found to be expressed differentially between the WnM and SM life-history states. These genes were enriched for physiological pathways that might be involved in the regulation of seasonal migrations in birds. For example, genes for the ATP binding pathway in the hypothalamus were expressed at a significantly higher level in SM than in the WnM life-history state. Likewise, upregulated genes associated with the myelin sheath and focal adhesion were enriched in the hypothalamus, and those with cell-to-cell junction, intracellular protein transport, calcium ion transport and small GTPase-mediated signal transduction were enriched in the liver. Many of these genes are a part of physiological pathways potentially involved in the regulation of seasonal migration in birds. These results show molecular changes at the regulatory and metabolic levels associated with seasonal transitions in a long-distance migrant and provide the basis for future studies aimed at unravelling the genetic control of migration in birds.

Settling down of seasonal migrants promotes bird diversification

How seasonal migration originated and impacted diversification in birds remains largely unknown. Although migratory behaviour is likely to affect bird diversification, previous studies have not detected any effect. Here, we infer ancestral migratory behaviour and the effect of seasonal migration on speciation and extinction dynamics using a complete bird tree of life. Our analyses infer that sedentary behaviour is ancestral, and that migratory behaviour evolved independently multiple times during the evolutionary history of birds. Speciation of a sedentary species into two sedentary daughter species is more frequent than speciation of a migratory species into two migratory daughter species. However, migratory species often diversify by generating a sedentary daughter species in addition to the ancestral migratory one. This leads to an overall higher migratory speciation rate. Migratory species also experience lower extinction rates. Hence, although migratory species represent a minority (18.5%) of all extant birds, they have a higher net diversification rate than sedentary species. These results suggest that the evolution of seasonal migration in birds has facilitated diversification through the divergence of migratory subpopulations that become sedentary, and illustrate asymmetrical diversification as a mechanism by which diversification rates are decoupled from species richness.

Helminth community structure study on urban and forest blackbird (Turdus merula L.) populations in relation to seasonal bird migration on the south Baltic Sea coast (NW Poland)

Abstract The aim of the study was to compare helminth community structure of urban and forest blackbird populations. 24 helminth species in 98 blackbirds were found. Higher species richness was noted in the forest population of the blackbird (23 species) in comparison to the urban population (14 species). The response of the helminth fauna to a synanthropic habitat, contrary to a natural habitat, consists in a significant reduction in most parasitological parameters. Higher species richness has been noted in spring (17 species) than in autumn (14 species). Urban habitat, in contrast to the forest, may cause changes in the abundance of helminth communities in male and female blackbirds. The helminth fauna of nestlings, in spite of low species richness is characterized by a higher prevalence and intensity of infection in comparison to blackbirds feeding on their own. Helminth fauna of the blackbird seems to be a good indicator of environmental quality.

Burullus Ringing Station (N Egypt) – Ringing Results and Seasonal Bird Migration Dynamics in 2005-2007

ABSTRACT Zaniewicz G., Chruoeciel J. 2011. Burullus ringing station (N Egypt) - ringing results and seasonal bird migration dynamics in 2005-2007. Ring 33, 1-2: 77-87. Burullus Ringing Station is one of the several stations belonging to the SEEN organization (SE European Bird Migration Network). This station is situated close to the border of Burullus Protected Area in the northern part of Egypt and it started work in 2005. Data were collected during two spring and three autumn seasons. Birds were caught in mist-nets, which were placed mainly in reedbeds. Over 12 thousands of birds from 74 species were caught and ringed during five migratory seasons. Many of them were also tested for directional preferences in Busse’s cage.

Accuracy and Resolution Capacity of MRL-5(Is) Radar Ornithological Station and its Potential Development

Abstract Dinevich L., Leshem Y. 2012. Accuracy and resolution capacity of MRL-5(Is) radar ornithological station and its potential development. Ring 34: 3-21. The paper presents the comprehensive assessment of the resolution capacity of MRL-5(Is) radar ornithological station developed in Israel. Theoretical calculations, as well as experimental testing and field experience enable the authors to evaluate the station’s performance and to suggest new directions of its potential development. The computer-controlled system is able to select bird echoes and plot ornithological charts for distances up to 60 km. Under conditions of normal refraction at distances of 5-25 km, MRL-5(Is) is able to detect all the birds (undisguised by hills) at the horizon level. A bird as big as a stork flying 100 m higher than the radar location reflects an echo strong enough to be detected by the radar at the distance of 90 km. In the daytime, at the distance of up to 60 km from the radar, under conditions of the open horizon, the station detects 56-83% of migrating birds flying at the altitude of over 100 m above the radar location. At night, at the distance of up to 30 km from the radar, the station detects 74-89% of migrating birds flying at 150 m above the radar location. At the distances of 20 and 50 km, the resolution capacity of the station (i.e. detecting separated echoes of two or more birds flying at a distance from each other) are Δr = 200 m and Δr = 400 m, respectively; regarding the height and the tangential component; distance-wise, the capacity is 150 m regardless of the distance to the target. Systematic observations of seasonal bird migration in the daytime and at night conducted during two autumn seasons and two spring seasons showed that the number of birds flying via Israel is significantly lower in spring than in autumn.

Optimal Gabor-Frame-Expansion-Based Intermittent-Clutter-Filtering Method for Radar Wind Profiler

Abstract Intermittent clutter signals are frequently observed by radar wind profilers during the seasonal bird migration. A novel statistical filtering algorithm based on a simultaneous time–frequency analysis of the profiler’s raw data was recently proposed to address shortcomings of existing methods. The foundation of this method is a Gabor frame expansion of the complex time series of the demodulated receiver voltage. In this paper, two objective criteria are suggested to obtain an optimal setup for the discrete Gabor frame expansion from the multitude of possibilities: first, the choice of almost-tight frames for a predefined maximum redundancy and second, the requirement that the analyzing bandwidth of the used Gaussian window function should provide a simultaneously sparse representation of both atmospheric signal components and intermittent clutter. The question of optimal sampling settings, especially dwell time, for a maximum reduction of bird interference is also discussed. Using data obtained during intense bird migration events it is shown that a combination of filtering and quality control of the result is required to prevent the occurrence of significant systematic and correlated errors in the final wind measurement.

Ancestry and evolution of seasonal migration in the Parulidae

Seasonal migration in birds is known to be highly labile and subject to rapid change in response to selection, such that researchers have hypothesized that phylogenetic relationships should neither predict nor constrain the migratory behaviour of a species. Many theories on the evolution of bird migration assume a framework that extant migratory species have evolved repeatedly and relatively recently from sedentary tropical or subtropical ancestors. We performed ancestral state reconstructions of migratory behaviour using a comprehensive, well-supported phylogeny of the Parulidae (the 'wood-warblers'), a large family of Neotropical and Nearctic migratory and sedentary songbirds, and examined the rates of gain and loss of migration throughout the Parulidae. Counter to traditional hypotheses, our results suggest that the ancestral wood-warbler was migratory and that losses of migration have been at least as prevalent as gains throughout the history of Parulidae. Therefore, extant sedentary tropical radiations in the Parulidae represent losses of latitudinal migration and colonization of the tropics from temperate regions. We also tested for phylogenetic signal in migratory behaviour, and our results indicate that although migratory behaviour is variable within some wood-warbler species and clades, phylogeny significantly predicts the migratory distance of species in the Parulidae.

Spring Migration of RuffsPhilomachus pugnaxin Fryslân: Estimates of Staging Duration Using Resighting Data

Seasonal bird migration involves long flights, but most time is actually spent at intermediate staging areas. The duration of stay at these sites can be evaluated with mark—recapture methods that employ day-to-day local encounters of individually marked birds. Estimates of staging duration are based on two probabilities: the immigration probability, the complement of a bird's seniority to an area, and the emigration probability, the complement of the staying probability. Estimating total staging duration from seniority and staying probabilities requires validation for resighting data and here we compare three data categories of Ruffs Philomachus pugnax passing through The Netherlands during northward migration: (1) newly colour-ringed, (2) previously colour-ringed and (3) radio-tagged Ruffs (recorded by automated receiving stations). Between 2004 and 2008, 4363 resighting histories and 95 telemetry recording histories were collected. As sample sizes for females were low, only data for males were analysed. Possible catching effects affecting estimates of staging duration were explored. Staying probability was estimated for all data. Seniority however, could not be estimated for newly marked Ruffs; the assumption of equal ‘capture’ probability for reverse-time models applied to estimate seniority is violated for seasonal resighting histories starting with a catching event. Therefore, estimates of total staging duration were based on resightings of previously colour-marked birds only. For radio-tagged birds a minimal staging duration (time between tagging and last recording) was calculated. Modelling indicated that newly colour-ringed birds had a higher staying probability than previously colour-ringed birds, but the difference translated to a prolonged staging duration in newly ringed birds of only 0.4–0.5 d, suggesting a very small catching effect. The minimal staging duration of radio-tagged birds validated estimates of staging duration for colour-ringed birds in 2007 but not in 2005. In 2005 a low resighting probability resulted in underestimates of staging duration. We conclude that (1) estimates of staying probability can be affected by catching although effects on staging duration might be small, and that (2) low resighting probabilities can lead to underestimates in staging duration. In our study previously ringed Ruffs resighted in 2006–08 yielded reliable estimates of staging duration as data had sufficiently high resighting probabilities. Average staging durations varied between 19 d in 2008 and 23 d in 2006.

Radar monitoring of seasonal bird migration over central Israel

Radar monitoring of seasonal bird migration over central Israel A radar ornithological station has been created based on the meteorological radar MRL-5 and a specially designed algorithm. The system enables to plot radar charts within the radius of 60 km combining meteorological data with vectors of bird field flying at different heights and pass these charts online over to air traffic control operators. The data accumulated in the study made it possible to obtain certain characteristics of seasonal bird migration over central Israel. The system and the results of the study have become an integral part of ensuring air safety for Israeli military aircraft. The paper is an overview and summary of a development of the system, which was described in a few earlier publications.

Advanced intermittent clutter filtering for radar wind profiler: signal separation through a Gabor frame expansion and its statistics

Abstract. A new signal processing method is presented for the suppression of intermittent clutter echoes in radar wind profilers. This clutter type is a significant problem during the seasonal bird migration and often results in large discrepancies between profiler wind measurements and independent reference data. The technique presented makes use of a discrete Gabor frame expansion of the coherently averaged time series data in combination with a statistical filtering approach to exploit the different signal characteristics between signal and clutter. The rationale of this algorithm is outlined and the mathematical methods used are presented in due detail. A first test using data obtained with an operational 482 MHz wind profiler indicates that the method outperforms the previously used clutter suppression algorithm.