Autumn Migration Period Research Articles

Shoreline Translocation during Road Expansion Was Successful for Most Waterbirds but Not for Waders

Coastal wetlands are one of the most threatened ecosystems due to, firstly, their relative rarity and, secondly, the strong human interest in these coastal sites for infrastructure development, and recreation. These coastal wetlands also serve as important migration stopover sites for a range of waterbirds. There is great international interest in mitigating the negative effects of human land development and in restoring degraded habitats. I evaluated the response of one waterbird community to the mitigation action implemented during road expansion in an important waterbird coastal habitat in central Norway. Using a novel mitigation method, the shoreline was moved seawards to allow space for a continued shoreline habitat and the extended road. By weekly monitoring the waterbird community during spring and autumn migration periods (n = 7 of each), I found similar biodiversity, evenness, and abundance of geese, dabbling ducks, diving ducks, gulls, and waders when data for the whole wetland were used. However, after construction waders were partially displaced from the zone closest to the road to a zone further away. For some groups of birds, shoreline translocation can be a fruitful mitigation action aiming to reduce the negative effects of infrastructure expansion in coastal areas.

Factors influencing migration of short-finned eels (Anguilla australis) over 3 years from a wetland system, Lake Condah, south-east Australia, downstream to the sea.

Anguillid eel populations are under threat globally. A particularly vulnerable life-cycle stage is the migration of mature adult eels downstream from freshwater habitats through estuaries into the sea to spawn. This study investigated the factors associated with downstream migration of the short-finned eel Anguilla australis (Richardson 1841) from a coastal wetland (Lake Condah) in south-east Australia, using acoustic telemetry. Migration was associated with time of the year, higher water level and river flows, decreasing water temperature, and darker moon phases. Larger individuals and those in better condition were more likely to migrate from the wetland. Downstream migration peaked in spring, in contrast to the typical autumn migration period for other temperate anguillids. Variable responses, in comparison to other studies, highlight how migration cues may not be universal. In south-east Australia, short-finned eels may have evolved to migrate in multiple phases by first migrating to the estuary during typical seasonal spring flow pulses (e.g., to avoid being stranded in upland reaches during dry summer periods) and then migrating into the ocean in autumn. More research is needed to unravel these processes and causes, especially considering that the relationship between migration and hydrology may be complex and confounded (e.g., by human-induced disruptions to migratory pathways).

The Circadian Rhythm of the Behavior and Gut Microbiota in Dybowski's Frogs (Rana dybowskii) during the Autumn Migration Period.

Many amphibian behaviors and physiological functions adapt to daily environmental changes through variations in circadian rhythms. However, these adaptations have yet to be reported in Dybowski's frog (Rana dybowskii). We aimed to elucidate the dynamic changes in the behavior and gut microbiota of R. dybowskii within a 24 h cycle during their migration to hibernation sites. Thus, we monitored their behavior at 4 h intervals and collected samples for microbiome analysis. We found that the juvenile frogs arrived at hibernation sites earlier than the adults. Among the adults, the male frogs arrived earlier. The richness and diversity of the gut microbiota in the adult R. dybowskii were lowest at 14:00. At 6:00, the differences between the males and females were most significant. At 18:00, there was an increase in the activity of Bacteroides, Coprobacillus, Ruminococcus, and Dorea in the intestinal tracts of the male frogs, whereas in the intestinal tract of the female frogs, there was an increase in the activity of Pseudoramibacter_Eubacterium, Desulfovibrio, Anaerotruncus, and PW3. This indicated diurnal rhythmic variations in the gut microbiota and significant sex-based differences in the microbial activity at different time points. Our findings contribute to the understanding of the circadian rhythm of R. dybowskii and provide crucial insights into improving breeding strategies.

Concentration of metals and metalloids in livers of birds of various foraging guilds collected during the autumn migration period in Poland.

During migration, birds explore various habitats at stopover sites that differ in food resources and contamination levels. In this study, hepatic concentrations of 21 elements (metals and metalloids) in 11 species of birds, representing various foraging habitats (such as aquatic, aquatic/terrestrial, and terrestrial) and migration modes (migratory and sedentary) representing various foraging guilds (omnivores, piscivores, and molluscivores), were analyzed. The samples (N = 84) were collected during the autumn migration period in Poland. The concentrations of elements determined in this study exhibited high inter-species variability, reflecting the diversity in contamination levels depending on food resources used by specific bird groups. Many of the investigated individuals from different species showed exceeded levels of subclinical toxicity and moderate clinical poisoning due to Cd and Hg. Higher concentrations of As, Hg, and Ba and lower V concentrations were found in migratory birds as compared to sedentary birds. Species foraging in terrestrial habitat had different concentrations of some elements compared to aquatic and aquatic/terrestrial species. Some specific inter-species differences in hepatic elemental concentrations were found. Differences in elemental concentrations among various groups can primarily be attributed to their foraging guilds, with certain elements, particularly As, V, and Hg, playing a significant role in the dissimilarity of elemental concentrations between foraging habitat groups and migratory mode groups. The data collected confirmed the limited ability of As to enter ecosystem pathways. The results of this study contribute to understanding the year-round exposure of migratory birds to environmental contamination, which can have carry-over effects on their performance in wintering and breeding grounds.

The contribution of individual characteristics of <i>Anas</i> and <i>Aythya</i> individuals to their susceptibility to low‐pathogenic avian influenza viruses in the south of Western Siberia

Aim. Analysis of the influence of species, sex, and age of genus Anas and Aythya individuals on their sensitivity to low pathogenic avian influenza viruses (LPAIV) in the south of Western Siberia. Material and Methods. Infestation of ducks with the influenza virus was determined by cloacal swabs obtained from 5014 individuals of ducks belonging to the genus Anas and Aythya during the autumn migration period in the south of Western Siberia. Isolation of influenza A virus isolates was carried out according to standard WHO methods. The distribution of infected individuals was estimated with ꭓ2. Relative risk (RR) was used to estimate the risk of infection for each individual species. Results. Among the examined ducks, the distribution between species differed between infected and uninfected individuals. The common teal was under greater risk of being infected with the avian influenza virus. In this species, the sex of the individual influenced the probability of infestation both in young individuals and the whole age spectrum. Conclusions. Individual characteristics of wild dabbling and diving ducks (species, sex, age) affect their infestation with low‐pathogenic avian influenza virus during the autumn migration period in the south of Western Siberia.

The War-Damaged Urban Environment Becomes Deadly Trap for Bats: Case from Kharkiv City (NE Ukraine) in 2022

Abstract The full-scale war in Ukraine negatively impacted populations of urban and semi-urban animals. This study examines the effects of war-related damages on urban populations of bats in Kharkiv city (NE Ukraine) during 2022. Our findings suggest that 45.1% of buildings used as wintering roosts for N. noctula were either partially damaged or completely destroyed by shellings, which may have led to the direct killing of approximately 7,000 bats. Additionally, the war-damaged urban environments in Kharkiv serve as a deadly trap for bats during the period of autumn migration or swarming. Bats flew into buildings’ interiors through windows that were left open or broken by blast waves, resulting in entrapment. The total number of N. noctula trapped inside buildings damaged by shelling was 2,836 individuals, with a death rate of approximately 30%. The group size of trapped bats was more numerous than in previous years, and the main findings were concentrated in war-damaged districts of the city.

Factors that influence aerial line transect detection of BeringChukchi-Beaufort Seas bowhead whales

This paper presents a rich, complex dataset including 25 years of aerial line transect surveys for bowhead whales in the Bering, Chukchi and Beaufort Seas, for which a distance detection function was estimated. The analysis was limited to the autumn migratory period and to the portions of the Beaufort and Chukchi Seas occupied by bowhead whales during this period. The primary purpose of the work was to improve the understanding of what factors significantly affect detection. Comprehensive model selection efforts based on the AIC identified useful predictors. Results showed that Beaufort Sea state, ocean depth, inter-sighting waiting distance and year were among the factors affecting detections. For example, increased depth and long wait distances between sightings were both associated with narrower effective strip widths. Some of the results can be interpreted as evidence for a relationship between detection probabilities and whale behaviour. The complexity of the overall dataset required substantial data organisation and offered many alternative analysis approaches, but the results were fairly consistent across such choices. Notwithstanding successful estimation of the detection function, the data present substantial challenges to standard abundance estimation using line transect methods.

White-Nose Syndrome Pathogen Pseudogymnoascus destructans Detected in Migratory Tree-Roosting Bats.

White-nose syndrome (WNS) is an emerging fungal epizootic disease that has caused large-scale mortality in several species of North American bats. The fungus that causes WNS, Pseudogymnoascus destructans (Pd), has also been detected in bat species without diagnostic signs of WNS. Although these species could play a role in WNS spread, understanding of the spatial and temporal extents of Pd occurrence on WNS-resistant species is limited. This study evaluated the presence of Pd on 272 individuals of three species of migratory tree-roosting bats: hoary (Lasiurus cinereus), eastern red (Lasiurus borealis), and silver-haired (Lasionycteris noctivagans) bats, obtained opportunistically during summer and autumn from throughout much of their ranges in North America. We also compared tissue sampling protocols (i.e., tissue swabbing, fur swabbing, and DNA extraction of excised wing tissue). We detected Pd on three eastern red bats from Illinois and Ohio, US, one silver-haired bat from West Virginia, US, and one hoary bat from New York, US, all via DNA extracted from wing tissue of carcasses. These results document the first publicly reported detections of Pd on a hoary bat and on migratory bats during the autumn migratory period, and demonstrate the potential for using carcasses salvaged at wind-energy facilities to monitor for Pd.

Do Nearctic hover flies (Diptera: Syrphidae) engage in long‐distance migration? An assessment of evidence and mechanisms

AbstractLong‐distance insect migration is poorly understood despite its tremendous ecological and economic importance. As a group, Nearctic hover flies (Diptera: Syrphidae: Syrphinae), which are crucial pollinators as adults and biological control agents as larvae, are almost entirely unrecognized as migratory despite examples of highly migratory behavior among several Palearctic species. Here, we examined evidence and mechanisms of migration for four hover fly species (Allograpta obliqua, Eupeodes americanus, Syrphus rectus, and Syrphus ribesii) common throughout eastern North America using stable hydrogen isotope (δ2H) measurements of chitinous tissue, morphological assessments, abundance estimations, and cold‐tolerance assays. Although further studies are needed, nonlocal isotopic values obtained from hover fly specimens collected in central Illinois support the existence of long‐distance fall migratory behavior in Eu. americanus, and to a lesser extent S. ribesii and S. rectus. Elevated abundance of Eu. americanus during the expected autumn migratory period further supports the existence of such behavior. Moreover, high phenotypic plasticity of morphology associated with dispersal coupled with significant differences between local and nonlocal specimens suggest that Eu. americanus exhibits a unique suite of morphological traits that decrease costs associated with long‐distance flight. Finally, compared with the ostensibly nonmigratory A. obliqua, Eu. americanus was less cold tolerant, a factor that may be associated with migratory behavior. Collectively, our findings imply that fall migration occurs in Nearctic hover flies, but we consider the methodological limitations of our study in addition to potential ecological and economic consequences of these novel findings.

Changes in waterfowl migration phenologies in central North America: Implications for future waterfowl conservation.

Globally, migration phenologies of numerous avian species have shifted over the past half-century. Despite North American waterfowl being well researched, published data on shifts in waterfowl migration phenologies remain scarce. Understanding shifts in waterfowl migration phenologies along with potential drivers is critical for guiding future conservation efforts. Therefore, we utilized historical (1955–2008) nonbreeding waterfowl survey data collected at 21 National Wildlife Refuges in the mid- to lower portion of the Central Flyway to summarize changes in spring and autumn migration phenology. We examined changes in the timing of peak abundance from survey data at monthly intervals for each refuge and species (or species group; n = 22) by year and site-specific temperature for spring (Jan–Mar) and autumn (Oct–Dec) migration periods. For spring (n = 187) and autumn (n = 194) data sets, 13% and 9% exhibited statistically significant changes in the timing of peak migration across years, respectively, while the corresponding numbers for increasing temperatures were 4% and 9%. During spring migration, ≥80% of significant changes in the timing of spring peak indicated advancements, while 67% of significant changes in autumn peak timing indicated delays both across years and with increasing temperatures. Four refuges showed a consistent pattern across species of advancing spring migration peaks over time. Advancements in spring peak across years became proportionally less common among species with increasing latitude, while delays in autumn peak with increasing temperature became proportionally more common. Our study represents the first comprehensive summary of changes in spring and autumn migration phenology for Central Flyway waterfowl and demonstrates significant phenological changes during the latter part of the twentieth century.

An Observation of Spring Mating in Silver-Haired Bats (Lasionycteris noctivagans)

The mating behavior of North American tree bats (Lasiurus spp. and Lasionycteris noctivagans) is not well understood. The majority of records suggest that this group of species mates during the autumn migratory period and that females store sperm throughout the winter before resuming the reproductive cycle in spring. On 16 May 2019, while mist-netting in Bernalillo County, New Mexico, USA, we observed a male and female silver-haired bat (Lasionycteris noctivagans) copulating on the ground. Both individuals were captured and processed to obtain further details on reproductive status. To our knowledge this is the first published record of a silver-haired bat copulation event, and its occurrence during the spring migratory period challenges long-held assumptions about the reproductive cycle of the species and tree bats in general.

Association of weather variables with the migration phenology and body conditions of Siberian warblers

Different elements of weather, such as wind speed, wind direction, precipitation and temperature are very important regulators of bird migration. Weather conditions also play role on the body condition such as body mass and the deposited fat. In this study we selected four warbler species to examine the impact of different weather variables on their spring and autumn migration timing and their body condition in one of the most extreme weather areas of the Earth, at Lake Baikal in Siberia. We also studied the changes in body mass and fat reserves during the spring and autumn migration periods of these species. For the analyses, we used ringing data of 2471 birds from five spring and five autumn seasons during 2015–2019. According to our results, it can be stated that the weather did not have a significant association with the migration timing of the studied warblers, perhaps due to the geographical location of the study site. However, the body mass and the fat reserves of the birds increased during unsuitable weather conditions because of the increased energy requirements. Birds generally migrate with low fat reserves, which is due to the fact that this area is not an important stopover site for these species.

Flight training and dietary antioxidants have mixed effects on the oxidative status of multiple tissues in a female migratory songbird.

Birds, like other vertebrates, rely on a robust antioxidant system to protect themselves against oxidative imbalance caused by energy-intensive activities such as flying. Such oxidative challenges may be especially acute for females during spring migration, as they must pay the oxidative costs of flight while preparing for reproduction; however, little previous work has examined how the antioxidant system of female spring migrants responds to dietary antioxidants and the oxidative challenges of regular flying. We fed two diets to female European starlings, one supplemented with a dietary antioxidant and one without, and then flew them daily in a windtunnel for 2weeks during the autumn and spring migration periods. We measured the activity of enzymatic antioxidants (glutathione peroxidase, superoxide dismutase and catalase), non-enzymatic antioxidant capacity (ORAC) and markers of oxidative damage (protein carbonyls and lipid hydroperoxides) in four tissues: pectoralis, leg muscle, liver and heart. Dietary antioxidants affected enzymatic antioxidant activity and lipid damage in the heart, non-enzymatic antioxidant capacity in the pectoralis, and protein damage in leg muscle. In general, birds not fed the antioxidant supplement appeared to incur increased oxidative damage while upregulating non-enzymatic and enzymatic antioxidant activity, though these effects were strongly tissue specific. We also found trends for diet×training interactions for enzymatic antioxidant activity in the heart and leg muscle. Flight training may condition the antioxidant system of females to dynamically respond to oxidative challenges, and females during spring migration may shift antioxidant allocation to reduce oxidative damage.

New information on the bar-tailed godwit Limosa lapponica (Linnaeus, 1758) and red-throated diver Gavia stellata (Pontoppidan, 1763) on the Crimean Peninsula (the Black Sea)

New data on the distribution of the bar-tailed godwit Limosa lapponica (Linnaeus, 1758) and red-throated diver Gavia stellata (Pontoppidan, 1763) on the Crimean Peninsula are presented. Against the backdrop of aquatic and coastal ecosystems’ transformation under natural and anthropogenic impact, even single finds of hydrophilic avifauna representatives in atypical spatiotemporal conditions are of interest for the analysis of emerging trends in migration phenology and abundance of both separate species and taxonomic and ecological groups of birds. The aim of the study was to clarify the distribution boundaries and terms of stay on the Crimean Peninsula of two hydrophilic bird species: semiaquatic species, bar-tailed godwit, and true water bird, red-throated diver. Bird observations were carried out during scheduled accountings on the Isthmus of Ak-Monay (March 2012) and in the Kruglaya Bay (Sevastopol) (July 2019). The bar-tailed godwit is registered in Crimea during spring and autumn migration periods. For the first time, it was found in the north of the Crimean Peninsula in 1972; later, there were an increase in its abundance and expansion of a distribution area. Recent records of this species in southern Crimea significantly expanded the known boundaries of its distribution on the peninsula during the migration period. The observation of the bar-tailed godwit in eastern Crimea on 14 March, 2012, specified the date its spring migration begins; the observation in Sevastopol (western foothill) on 27 July, 2019, was the first one in Mountain Crimea. Off the Crimean coast, the red-throated diver is a rare overwintering and migratory bird. The find of the red-throated diver individual in the Kruglaya Bay on 19 January, 2020, was the third reliable record of this species overwintering in Crimea and the first one in Sevastopol area. The registration of the red-throated diver at a considerable distance from its usual overwintering areas (off the southwestern coast of the Black Sea), along with numerous facts of the expansion of nesting or winter ranges of different bird species northward, confirms the ongoing climatic and ecological changes. Particular attention should be focused on the problem, associated with low ecological culture of the use and disposal of fishing tackles, which have a detrimental effect on hydrophilic birds. Measures have to be developed to regulate fishing with nets, hooks, and line tackles in the areas of bird mass overwintering and seasonal migrations.

Modelling population dynamics and trends in migratory birds from non-standardized multi-species ringing data: the potential of multi-model selection

ABSTRACT Capsule Long-term and non-standardized migratory bird ringing data can be used in models controlling variation in bird ringing methodology for reliable population trend estimations. Aims Bird ringing data usually cover long periods and might reflect long-term population changes. However, they are mainly derived during non-standardized multi-species catching at numerous sites during the autumn migration period. We searched for the best modelling approach to determine reliable species population dynamics and trend estimation models based on annual multi-species bird ringing data. Methods We used ringing data from the Slovenian Bird Ringing Scheme and selected data in three steps according to temporal, quantitative, and qualitative data selection. Annual indices were constructed based on two types of denominators, ringing days, and ringing totals, vs. a robust model without a denominator. We ran 20 candidate-generalized additive models describing migrating population dynamics for 15 bird species by combining different data selection approaches and denominators. Results We found that the models were species-specific, although the universal model could also be applied to most species. We propose a general model construction approach for population trend assessments from non-standardized bird ringing data. The estimates obtained by this approach were comparable to the overall European population trends derived from breeding survey data. Conclusions Bird ringing data from the autumn migration period are a valuable resource for assessing continental scale population trends taking into account the whole population (non-breeders and juveniles included) and even some rare and endangered species, but should be conducted according to standard protocols to ensure reliable statistical inference of population trends.

Misidentifications in citizen science bias the phenological estimates of two hard‐to‐identify Elaenia flycatchers

Citizen science initiatives contain a large volume of observations that can be useful to address ecological questions for a wide array of organisms. However, one limitation of citizen science data is the potential for species misidentification. Although recent studies have shown that citizen science data are relatively accurate for many taxa, the effect of misidentification errors in hard‐to‐identify species remains poorly explored. If misidentification events occur at large scales, ecological estimates can be compromised. Here, we show that misidentifications contained in citizen science databases biased phenological estimates in a pair of migratory and partially overlapping Neotropical flycatchers: the Chilean Elaenia Elaenia chilensis and the Small‐billed Elaenia Elaenia parvirostris. We reviewed and re‐classified 4399 photos of these species from Argentina, Chile and Uruguay. We found that overall identification accuracy was high (c. 90%) for both species when they were allopatric, but dramatically low for Small‐billed Elaenia during autumn migration (from 28.6% to 84.6%) because migrating individuals of Chilean Elaenia were systematically reported as Small‐billed. The phenological estimates for both Elaenias were biased due to the large number of misidentifications concentrated towards the autumn migration period. These errors caused a 1‐week advancement in the estimated arrival, and a 2‐week delay in the estimated departure for Small‐billed Elaenia. For Chilean Elaenia, errors caused a 1‐week delay for the estimated spring peak passage and underestimation of the magnitude of the autumn passage. Our results highlight the importance of performing critical assessments of records when using citizen science databases to describe ecological patterns in species that are hard to identify. The large volume of information provided by citizen science initiatives is useful to describe spatio‐temporal patterns in birds, particularly in those of poorly known regions. However, to further enhance the usefulness of such databases, it is imperative actively to post‐process and contrast patterns derived from documented (and undocumented) records, with a special focus on misidentifications. This will only be possible through a thorough review of the documented data, together with an intimate understanding of the natural history of the study species.

Акустичний моніторинг кажанів: досвід організації на заповідних територіях Поділля

Most of the available data on bats in the national park are related to the monitoring of their number in wintering sites, and the study of summering bat populations remains an important task for further monitoring of biodiversity of the Podilski Tovtry National Nature Park. Bats are an important indicator group of animals for assessing the state of conservation of faunal groups and studying the dynamics of biodiversity of nature reserves. Bats depend on the availability of suitable sites and are the first to respond to changes in the natural habitat. Acoustic monitoring was carried out using an Echo Meter Touch Ultrasonic Modules detector and a Xiaomi Mi A2 Lite smartphone. The analysis of sound signals was performed in the Echo Meter software (version 2.7.23) from Wildlife Acoustics, as well as in the Kaleidoscope bat software. Bats were also trapped using mist nets. Natural shelters were inspected using a Trotec BO26 professional endoscope. Ten species of bats were studied: Myotis nattereri, Myotis daubentonii, Plecotus auritus, Barbastella barbastellus, Nyctalus leisleri, Nyctalus noctula, Pipistrellus nathusii, Pipistrellus kuhlii, Pipistrellus pygmaeus, and Eptesicus serotinus. The most common are species of the genus Pipistrellus and the species Nyctalus noctula (47.5%). River valleys are important migration corridors for migratory animal species. Seasonal activity of bats on survey transects is characterized by two peaks: spring (May) and autumn (September) migration periods. Acoustic activity of bats on survey transects lasts for eight months, from March to November. Autumn migration activity is longer than in spring. In the first decade of October, several thousand individuals of Nyctalus noctula were recorded flying in the valley of the Muksha River, near Tarasivka village, Kamianets-Podilsky Raion. The obtained data will improve the performance of work on assessing the state of conservation of faunal groups and changes in natural ecosystems. Preliminary results of the study will contribute to the organization of the program of acoustic monitoring of bats of the Podilski Tovtry National Nature Park.

Circadian and Seasonal Patterns of Body Temperature in Arctic Migratory and Temperate Non-migratory Geese

Arctic migration presents unique challenges to circadian physiology. In addition to the metabolic cost of maintaining a relatively high body temperature (Tb) above ambient temperature, migratory birds are also exposed to rapidly changing light conditions as they transition between light-dark cycles and a 24-hour polar day. A previous study suggested that Arctic-migratory barnacle geese (Branta leucopsis) may utilise adaptive heterothermy (i.e., a controlled decrease in core Tb) during and around the autumn migratory period in order to minimise the metabolic cost of migration, but the impact of seasonally changing daylight conditions on other parameters of the circadian profile of Tb in these geese remained obscure. Here, we provide a detailed comparative analysis on the circadian rhythm of Tb and its seasonal development in free-living barnacle geese from three study populations that differ in their migratory behaviour and in the environments they occupy. We recorded abdominal Tb in non-migratory geese from a temperate breeding colony in Netherlands and in migratory geese from a colony in the Russian low Arctic, and analysed these data together with previously published Tb data on geese from a migratory colony in the high Arctic of Svalbard. We found that the circadian Tb profile in the barnacle goose was well aligned with the daily and seasonally changing daylight conditions. In the migratory populations, a fast re-entrainment of the rhythm and its phase was observed when zeitgeber conditions changed during migratory movements. The circadian rhythmicity of Tb was lost once the geese encountered permanent daylight at their northern staging and breeding sites. Circadian Tb rhythmicity was re-established when the period of permanent daylight ended, at rates corresponding to rates of seasonal changes in daylength in the high and low Arctic. Although our data corroborated findings of a decrease in daily mean Tb before autumn migration in both migratory populations in this study, the pre-migratory decrease in Tb was less drastic than previously reported. Moreover, in contrast to previous study, the decrease in Tb stopped at the onset of migration. Overall, our data reveal no evidence that heterothermy in the barnacle goose is functionally linked to migration.

Biological Properties and Genetic Characterization of Novel Low Pathogenic H7N3 Avian Influenza Viruses Isolated from Mallard Ducks in the Caspian Region, Dagestan, Russia.

Avian influenza viruses (AIVs) are maintained in wild bird reservoirs, particularly in mallard ducks and other waterfowl. Novel evolutionary lineages of AIV that arise through genetic drift or reassortment can spread with wild bird migrations to new regions, infect a wide variety of resident bird species, and spillover to domestic poultry. The vast continental reservoir of AIVs in Eurasia harbors a wide diversity of influenza subtypes, including both highly pathogenic (HP) and low pathogenic (LP) H7 AIV. The Caspian Sea region is positioned at the intersection of major migratory flyways connecting Central Asia, Europe, the Black and Mediterranean Sea regions and Africa and holds a rich wetland and avian ecology. To understand genetic reservoirs present in the Caspian Sea region, we collected 559 cloacal swabs from Anseriformes and other species during the annual autumn migration periods in 2017 and 2018. We isolated two novel H7N3 LPAIV from mallard ducks whose H7 hemagglutinin (HA) gene was phylogenetically related to contemporaneous strains from distant Mongolia, and more closely Georgia and Ukraine, and predated the spread of this H7 LPAIV sublineage into East Asia in 2019. The N3 neuraminidase gene and internal genes were prototypical of AIV widely dispersed in wild bird reservoirs sampled along flyways connected to the Caspian region. The polymerase and nucleoprotein segments clustered with contemporaneous H5 HPAI (clade 2.3.4.4b) isolates, suggesting the wide dispersal of H7 LPAIV and the potential of this subtype for reassortment. These findings highlight the need for deeper surveillance of AIV in wild birds to better understand the extent of infection spread and evolution along spatial and temporal flyways in Eurasia.

Challenges and benefits of using unstructured citizen science data to estimate seasonal timing of bird migration across large scales.

Millions of bird observations have been entered on online portals in the past 20 years either as checklists or arbitrary individual entries. While several hundred publications have been written on a variety of topics based on bird checklists worldwide, unstructured non-checklist observations have received little attention and praise by academia. In the present study we tested the suitability of non-checklist data to estimate key figures of large-scale migration phenology in four zones covering the whole of Finland. For that purpose, we analysed 10 years of ornithological non-checklist data including over 400 million. individuals of 115 bird species. We discuss bird- and human-induced effects to be considered in handling non-checklist data in this context and describe applied methodologies to address these effects. We calculated 5%, 50% and 95% percentile dates of spring and autumn migration period for all species in all four zones. For validation purposes we compared the temporal distributions of 43 bird species with migration phenology from standardized long-term ringing data in autumn of which 24 species (56%) showed similar medians. In a model approach, non-checklist data successfully revealed latitudinal migration progression in spring and autumn. Overall, non-checklist data proved to be well suited to determine descriptors of migration phenology in Northern Europe which are challenging to attain by any other currently available means. The effort-to-yield ratio of data processing was commensurate to the outcomes. The unprecedented spatiotemporal coverage makes non-checklist data a valuable complement to current migration databases from bird observatories. The basic concept of the present methodology is applicable to data from other bird portals, if combined with local field ornithological knowledge and literature. Species-specific descriptors of migration phenology can be potentially used in climate change studies and to support echo interpretation in radar ornithology.