Wintering Sites Research Articles

Differential responses to weather and land‐cover conditions explain spatial variation in winter abundance trends in a migratory bird of conservation concern

Abstract Effective conservation strategies for animal populations require knowledge of relationships between population dynamics and their environmental drivers. However, these processes often vary within animal populations, requiring site‐specific conservation planning. Given limited financial resources, identifying groups of sites with similar population dynamics can help practitioners efficiently implement conservation programs to larger areas. We evaluated spatial patterns and environmental drivers of wintering site trends in a migratory bird of conservation concern, the Greenland white‐fronted goose (Anser albifrons flavirostris). We used latent class analysis to identify trend patterns in 35 years of abundance data among 59 geographically discrete Greenland white‐fronted goose wintering sites. We developed a state‐space abundance model in a Bayesian framework to quantify the effects of weather and land‐cover conditions experienced throughout spring migration, summer breeding, autumn migration and wintering periods on variation in wintering site abundance. We identified two main patterns in Greenland white‐fronted goose abundance trends: northeastern wintering sites declined on average by 3% per year, while southwestern wintering sites declined on average by 14% per year. Differential responses to weather and habitat conditions likely explained variation among groups, as geese at southwestern wintering sites were more negatively affected by harsh weather conditions (e.g. low temperatures and high precipitation on breeding areas) and poor habitat conditions (i.e. low‐quality grasslands and croplands) on wintering areas. Future conservation efforts to improve the suitability and nutritional quality of agricultural areas, especially cereal croplands in autumn and early winter and grasslands in late winter and early spring, could potentially improve local habitat conditions, especially in the southwestern wintering sites where abundance declines were steepest. Synthesis and applications. We demonstrate the potential to delineate animal populations based on spatial patterns in population dynamics using long‐term abundance monitoring data, which are commonly the only available data for conservation practitioners. By grouping sites based on spatial patterns in local abundance trends, we can further test hypotheses about how these groups are differentially affected by changing environmental conditions. This information is important for informing efficient conservation planning over large areas when financial resources are limited.

An allometric approach to seasonal changes in intake rates of migratory shorebirds in the Bijagós Archipelago, Guinea‐Bissau

Shorebirds migrating along the East Atlantic Flyway must travel long distances from their breeding sites in arctic and subarctic regions to wintering areas in Europe and Africa. Selecting a winter location is an important decision, as it can have both immediate and future consequences. Shorebirds must ensure they have enough resources to fulfil their energetic requirements during winter, as well as during the fuelling phase, when they must accumulate fat stores for the return migration. Migratory shorebirds are declining worldwide, with several populations wintering in tropical Africa facing steep declines, particularly when compared with their conspecifics wintering in temperate Europe. However, one of the most important wintering sites in Africa remains relatively unstudied, the Bijagós Archipelago, Guinea‐Bissau. In this study, we quantify intake rates of eight migratory shorebird species wintering in the Bijagós and explore how these vary throughout their stay in the archipelago. Given the uncertainties associated with measurements of field intake rates, an allometric validation of our approach confirmed a slope comparable to that predicted by theory and verified in many situations. Contrary to our expectations, we found no evidence for an increase in intake rates in the fuelling period; in fact, decreases were noticeable in a few species over the non‐breeding season. The allometric relationship across species also confirmed the seasonally decreasing daily energetic intakes, particularly by smaller species. The comparison between the intake rates in the Bijagós and those reported in other wintering sites along the flyway highlights the particularly low values for Ringed Plover Charadrius hiaticula, Curlew Sandpiper Calidris ferruginea and Bar‐tailed Godwit Limosa lapponica. Limitations in intake rates and the associated energetic intake suggest that some species may be energetically constrained in the Bijagós, particularly during fuelling.

Ontogeny of migration destination, route and timing in a partially migratory bird.

In migratory animals, the developmental period from inexperienced juveniles to breeding adults could be a key life stage in shaping population migration patterns. Nevertheless, the development of migration routines in early life remains underexplored. While age-related changes in migration routes and timing have been described in obligate migrants, most investigations into the ontogeny of partial migrants only focused on age-dependency of migration as a binary tactic (migrant or resident), and variations in routes and timing among individuals classified as 'migrants' is rarely considered. To fill this gap, we study the ontogeny of migration destination, route and timing in a partially migratory red kite (Milvus milvus) population. Using an extensive GPS-tracking dataset (292 fledglings and 38 adults, with 1-5 migrations tracked per individual), we studied how nine different migration characteristics changed with age and breeding status in migrant individuals, many of which become resident later in life. Individuals departed later from and arrived earlier at the breeding areas as they aged, resulting in a gradual prolongation of stay in the breeding area by 2 months from the first to the fifth migration. Individuals delayed southward migration in the year prior to territory acquirement, and they further delayed it after occupying a territory. Migration routes became more direct with age. Individuals were highly faithful to their wintering site. Migration distance shortened only slightly with age and was more similar among siblings than among unrelated individuals. The large gradual changes in northward and southward migrations suggest a high degree of plasticity in temporal characteristics during the developmental window. However, the high wintering site fidelity points towards large benefits of site familiarity, prompting spatial migratory plasticity to be expressed through a switch to residency. The contrasting patterns of trajectories of age-related changes between spatial and temporal migration characteristics might reflect different mechanisms underlying the expression of plasticity. Investigating such patterns among species along the entire spectrum of migration tactics would enable further understanding of the plastic responses exhibited by migratory species to rapid environmental changes.

Evolution of leapfrog migration: A test of competition-based hypotheses.

Leapfrog migration is a common migration pattern in birds where the breeding and wintering latitudes between populations are in reversed latitudinal sequence. Competition for wintering and breeding sites has been suggested to be an ultimate factor, and several competitor-based hypotheses have been proposed to explain this pattern. If wintering sites close to the breeding sites are favored, competitive exclusion could force subdominant individuals to winter further away. Competitive exclusion could be mediated either through body size or by prior occupancy. The alternative "spring predictability" hypothesis assumes competition for sufficiently close wintering areas, allowing the birds to use autocorrelated weather cues to optimally time spring migration departure. To test predictions and assumptions of these hypotheses, we combined morphometrics, migration, and weather data from four populations of common ringed plover breeding along a latitudinal (56-68° N) and climatic gradient (temperate to Arctic). Critical for our evaluation was that two populations were breeding on the same latitude in subarctic Sweden with the same distance to the closest potential wintering site, but differed in breeding phenology, and wintered in West Africa and Europe, respectively. Thus, while breeding on the same latitude, their winter distribution overlapped with that of an Arctic and temperate population. Body size was largest within the temperate population, but there was no size difference between the two subarctic populations. Populations wintering in Europe arrived there before populations wintering in Africa. The largest variation in the arrival of meteorological spring occurred at the temperate breeding site, while there was almost no difference among the other sites. In general, temperatures at the northernmost wintering area correlated well with each breeding site prior to breeding site-specific spring arrival. Based on these observations, we conclude that competitive exclusion through body-size-related dominance cannot explain leapfrog migration. Furthermore, the assumptions on which the "spring predictability" hypothesis is based did not match the observed wintering ranges either. However, we could not reject the hypothesis that competitive exclusion mediated by prior occupancy in the wintering area could lead to leapfrog migration, and therefore, this hypothesis should be retained as working hypothesis for further work.

Winter movements and site fidelity of Trumpeter Swans (Cygnus buccinator) in the Nebraska Sandhills

Winter movements and site fidelity of Trumpeter Swans (Cygnus buccinator) in the Nebraska Sandhills

Migratory pathways and winter destinations of Northern Gannets breeding at Helgoland (North Sea): known patterns and increasing importance of the Baltic Sea

We analysed the migratory behaviour of adult Northern Gannets (Morus bassanus) breeding at Helgoland in the North Sea, based on data obtained from geolocation devices in the non-breeding season 2016–2017. Birds moved east and south-west to a broad range of wintering sites, ranging from the western Baltic Sea to North-West Africa. Three out of 12 birds spent the winter in Africa, while 9 birds wintered in Europe, with the primary wintering sites in the North Sea. All but one tagged bird spent some time in the Baltic Sea or in the transitional waters between the North Sea and Baltic Sea. We also analysed data from online databases (dofbasen.dk, ornitho.de) and the German Seabirds at Sea database to explore the extent to which Northern Gannets used the western Baltic Sea, as well as the Kattegat and Skagerrak, during the winter months. Records of Northern Gannets in Danish waters have increased substantially over the last 18 winters, with particular increases in the Baltic Sea. There was also a notable increase in sightings of Northern Gannets in German Baltic Sea waters, but this occurred later than in the more northerly Danish waters. Both analyses demonstrated that Northern Gannets explored the western part of the Baltic Sea, as well as the Kattegat and Skagerrak, increasingly intensively. This recent increase in sightings is in accord with the establishment and exponential increase in the nearest breeding colony of Northern Gannets at Helgoland.

Revisiting an Old Issue: Sex Identification of Short-eared Owls (Asio flammeus) at an Asian Wintering Site

Abstract At wintering sites of the migratory Short-eared Owl (Asio flammeus) in subtropical Asia, behavioral interactions between males and females are limited, and the body mass and plumage features between the sexes overlap significantly. Thus, sexing the species morphometrically for research and conservation activities is difficult. We aimed to develop a quantitative method for sexing Short-eared Owls, and we here present a new formula to do so using plumage features. We used a total of 198 Short-eared Owls (163 from bird rescue efforts at 15 airports and 35 preserved specimens from a museum in Taiwan) and carefully examined their morphological data and plumage images, then determined their sex using polymerase chain reactions of chromodomain helicase DNA-binding protein genes on sex chromosomes or gonad inspection. Eight of the ten traits we evaluated differed significantly between males and females. Females had a greater number of cross bars on primaries, secondaries, and outermost tail feathers; a higher proportion of yellowish-brown underwing coverage; and larger measurements in head length, bill length, tarsus length, and body mass. The best-fit model suggested simplifying the formula to just the proportion of the yellowish-brown underwing coverage, which provided sexing accuracy exceeding 95.9% for the 49 live individuals in the test data set and 94.3% for the 35 preserved specimens. This formula addresses the challenges posed by ambiguous individuals in the wintering region and offers an efficient and accurate means for sexing Short-eared Owls when DNA or gonad inspection is unavailable.

Genotype × environment interaction patterns of dry matter yield in meadow brome, orchardgrass, tall fescue, and timothy evaluated at harsh winter sites

AbstractBackgroundGenotype × environment interaction (GEI) slows genetic gains and complicates selection decisions in plant breeding programs. Forage breeding program seed sales often encompass large geographic regions to which the cultivars may not be adapted. An understanding of the extent of GEI in perennial, cool‐season forage grasses will facilitate improved selection decisions and end‐use in areas with harsh winters.MethodsWe evaluated the dry matter yield of nine meadow brome (Bromus biebersteinii Roemer & J. A. Schultes), nine orchardgrass (Dactylis glomerata L.), seven tall fescue (Lolium arundinaceum (Schreb.) Darbysh.), and 10 timothy (Phleum pratense L.) cultivars or breeding populations at seven high latitude and/or elevation locations in Canada and the United States from 2019 to 2021.ResultsFor each of the species, we found significant differences among the genotypes for dry matter yield across environments and found significant levels of GEI. Using site regression analysis and GGE biplot visualizations, we then characterized the extent of the interactions in each species. Except for tall fescue, there was little evidence for the broad adaptation of genotypes across locations.ConclusionsThis research adds further evidence to the limitations of perennial, forage breeding programs to develop widely adapted cultivars and the need to maintain regional breeding efforts.

Novel Genotype of HA Clade 2.3.4.4b H5N8 Subtype High Pathogenicity Avian Influenza Virus Emerged at a Wintering Site of Migratory Birds in Japan, 2021/22 Winter.

Surveillance of avian influenza virus (AIV) was conducted in the 2021-2022 winter season at a wintering site of migratory Anatidae in Japan. An H5N8 subtype high pathogenicity AIV (HPAIV) with a unique gene constellation and four low pathogenicity AIVs (LPAIVs) were isolated from environmental samples. The genetic origin of the HPAIV (NK1201) was determined with whole-genome sequencing and phylogenetic analyses. Six of NK1201's eight genes were closely related to HA clade 2.3.4.4b H5N8 subtype HPAIVs, belonging to the G2a group, which was responsible for outbreaks in poultry farms in November 2021 in Japan. However, the remaining two genes, PB1 and NP, most closely matched those of the LPAIVs H7N7 and H1N8, which were isolated at the same place in the same 2021-2022 winter. No virus of the NK1201 genotype had been detected prior to the 2021-2022 winter, indicating that it emerged via genetic reassortment among HPAIV and LPAIVs, which were prevalent at the same wintering site. In addition, experimental infection in chickens indicated that NK1201 had slightly different infectivity compared to the reported infectivity of the representative G2a group H5N8 HPAIV, suggesting that the PB1 and NP genes derived from LPAIVs might have affected the pathogenicity of the virus in chickens. Our results directly demonstrate the emergence of a novel genotype of H5N8 HPAIV through gene reassortment at a wintering site. Analyses of AIVs at wintering sites can help to identify the emergence of novel HPAIVs, which pose risks to poultry, livestock, and humans.

Current water pollution status at an important wintering site of the black-faced spoonbill Platalea minor in Xinghua Bay, south China

Xinghua Bay is one of the largest wintering sites of the black-faced spoonbill Platalea minor in mainland China. The ecosystem of Xinghua Bay has shown a deteriorating trend with the increasing pressure of economic development in recent decades. To understand the current conservation status of the wintering spoonbills in Xinghua Bay, we collected water samples along the coast of Xinghua Bay and important spoonbill habitats during the wintering period to analyze the pollution degree of 7 target heavy metals and organics. The Nemerow pollution index (NPI), heavy metal pollution index (HPI) and contamination degree (CD) were used to assess the heavy metal pollution levels. The ecological risk index of a target heavy metal (Efi) and potential ecological risk index of all target heavy metals (RI) were used to assess the ecological risk of heavy metals levels in Xinghua Bay. Positive matrix factorization (PMF) was used to determine the sources of heavy metals in coastal waters with the EPA PMF5.0 model. The results showed that there was moderate to very heavy pollution by heavy metals and moderate associated ecological risks in Xinghua Bay, in which Hg and Cd were the major heavy metal pollution sources, and the level of organic pollution was of serious concern. The use of fertilizers for cultured shellfish and aquaculture in and around the bay were the major cause of the excessive nitrogen and phosphorus levels, and factories surrounding Xinghua Bay were the major sources of heavy metals and organic pollution. We propose conservation measures to increase black-faced spoonbill population and enhance its habitats.

A potential wintering site of Swainson's Hawks (Buteo swainsoni) in the North Pacific plains of Costa Rica with notes on their behavior

A potential wintering site of Swainson's Hawks (Buteo swainsoni) in the North Pacific plains of Costa Rica with notes on their behavior

The state of stocks and catches of commercial fish species of the Azov and Black Seas for the period 2000–2020: dynamics and trends

The aim to review the state of stocks and fishing against the background of changes in habitat conditions, commercial fish species of the Azov and Black Seas for the period 2000–2020.Materials: Regular scientific research, including: hydrological, hydrochemical, hydrobiological studies, bottom trawl and pelagic lamparian ichthyological surveys; collection and analysis of commercial biological information; analysis of commercial statistical data.Novelty: The dynamics of the values and state of stocks of commercial fish species in the conditions of climate change is shown. In the Black Sea, the increase in the average temperature of the mixed layer, the deepening of the upper boundary of the thermocline in the summer, as well as the slowdown in the cooling of the sea in the autumn-winter period has a negative impact on the productivity of the boreal ichthyofauna and the sprat (sprat) fishery; changes the timing and intensity of migrations of some species of the Mediterranean ichthyofauna, their wintering sites, areas of formation of commercial clusters and, accordingly, the effectiveness of fishing. In the Sea of Azov, the increase in salinity caused by a steady reduction in the volume of freshwater runoff of the Don and Kuban rivers and its replacement by advection of the Black Sea waters is the most important abiotic factor in changing habitat conditions. The increase in the salinity of the Sea of Azov has led to the transformation of traditional hydro- and ichthyocenoses. The gradual transition of the Sea of Azov under the jurisdiction of the Russian Federation makes it possible to more effectively apply resource-saving and resource-restoring measures in order to develop the fisheries potential of this inland sea.As results: the results obtained in this work on the assessment of the impact of anthropogenic and climatic changes will be used to clarify the projected production (catch) of commercial fish.

Relationship between wintering site and survival in a migratory waterbird using different migration routes

When wintering at different sites, individuals from the same breeding population can experience different conditions, with costs and benefits that may have implications throughout their lifetime. Using a dataset from a longitudinal study on Eurasian Spoonbills from southern France, we explored whether survival rate varied among individuals using different wintering sites. In the last 13 years, more than 3000 spoonbills have been ringed as chicks in Camargue. These birds winter in five main regions that vary in both migratory flyway (East Atlantic vs. Central European) and migration distance (long-distance vs. short-distance vs. resident). We applied Cormack–Jolly–Seber models and found evidence for apparent survival to correlate with migration distance, but not with flyway. During the interval between the first winter sighting and the next breeding period, long-distance migrants had the lowest survival, independently of the flyway taken. Additionally, as they age, spoonbills seem to better cope with migratory challenges and wintering conditions as no differences in apparent survival among wintering strategies were detected during subsequent years. As dispersal to other breeding colonies was rarely observed, the lower apparent survival during this period is likely to be partly driven by lower true survival. This supports the potential role of crossing of natural barriers and degradation of wintering sites in causing higher mortality rates as recorded for a variety of long-distance migrants. Our work confirms variation in demographic parameters across winter distribution ranges and reinforces the importance of longitudinal studies to better understand the complex demographics of migratory species.

Barometric geolocators can reveal unprecedented details about the migratory ecology of small birds

Abstract Knowing the location of migratory birds throughout their annual cycle is fundamental for many questions in ornithology. Technological advances have provided several approaches, with increasing miniaturization allowing deployment on smaller and smaller birds. Here, we examine the strengths and limitations of barometric pressure geolocators (pressure tags), which have recently been shown to be extremely effective in tracking small birds (<25 g). The newly developed geolocation by pressure workflow (GeoPressureR) uses a global weather analysis dataset and hidden Markov movement model to reveal locations more accurately or continuously than can be achieved by other available light-weight devices (e.g., light-level geolocators, automated radio telemetry, and archival GPS tags). Additionally, pressure data can provide altitude information and document generally intractable flight behavior, as well as exact migratory phenologies. This new technology can be applied to important unresolved problems such as altitudinal migration, stopover site use, molt migration, vertical airspace use, and drivers of migratory flight initiation, duration, and direction. We provide an example of a pressure tag on a Swainson’s Warbler (Limnothlypis swainsonii) deployed on its breeding territory in Virginia, USA, revealing the complete story of its migration to and from Cuba, including its refined wintering site, stopover sites, and migration routes, all with precise timing. Studies relying on pressure tags are still subject to biases related to recovery of the devices for data extraction, and application to birds that exhibit extensive aerial movements (e.g., swallows and swifts) remains challenging. Widespread deployment of pressure tags could show unprecedented details of bird migration and other aspects of aerial behavior, which could benefit conservation and greatly enrich our understanding of avian movement ecology.

First results of measuring temperature in snow cover at a winter search site in Irkutsk

First results of measuring temperature in snow cover at a winter search site in Irkutsk

Cuba’s first motus tower for tracking migrant land birds

Cuba’s first motus tower for tracking migrant land birds Keith Hobson, Professor and Research Scientist at Environment and Climate Change Canada and Western University, discusses updates in the expansion of tracking migratory birds in Central and South America, and the Caribbean. The conservation of migratory birds requires basic knowledge of connectivity between population-specific breeding, wintering, and stopover sites. This recognition has encouraged several government and NGO initiatives since many migratory species cross international borders during their annual travels. While the task is immensely difficult, an array of new tools is now available to track even small birds (~10g) using both intrinsic (e.g. stable isotope or genetic markers) and extrinsic (e.g. attached electronic devices) methods.

Wintering Conditions and Heat Loss during Hibernation in the Brown Long-Eared Bat

The aim of this study was to estimate heat loss in the brown long-eared bat during hibernation depending on the refugioclimate conditions. The measured values of refugioclimate parameters were: ambient temperature (Ta) 3–10 °C, relative humidity (Rh) 74–98% and air velocity (v) 0.06–0.95 m/s. Heat loss was calculated using convective heat transfer equations. Mean heat loss amounted to 4 W/m2. The results were compared to the heat loss calculated based on the fat burned during hibernation. Bats flying into underground systems during the hibernation period were captured and their body mass was measured. A loss of body mass of 2.6 g over the 126 days of hibernation was observed. Heat loss equalled 3.115 W/m2K.The presented method of calculating energy expenditure allows for non-invasive monitoring of the heat and fat losses of bats during hibernation. Such research may find application in designing artificial wintering sites.

Migration routes of mute swans (Cygnus olor) in East Asia: First description of the Eastern and Western Chinese populations based on satellite tracking

The distribution and migration routes of the most studied swan species, mute swans (Cygnus olor), in East Asia are largely unknown because most of those studies were conducted in Europe and North America. In 2016 and from 2021 to 2022, we deployed satellite tracking devices on 22 and 10 mute swans wintering at the Ili River, Xinjiang of Western China, and summering at Ulansuhai Lake, Inner Mongolia of Eastern China, to determine their migration routes. Eight environmental factors, namely, human population density, the shortest distance to the nearest transportation route, elevation, aspect, slope, air temperature, wind speed and gross primary productivity (GPP), were used to analyse the environmental differences at the stopover sites of swan populations between Eastern and Western China. Ebinur and Ulungur Lakes in Xinjiang of Western China and Kapchagay Reservoir and Sasykkol and Alakol Lakes in Eastern Kazakhstan were the summering sites for the Western Chinese swan population; for the Eastern Chinese swan population, in addition to the Yellow River Delta being identified as a wintering site, the Hongze Lake Region of Jiangsu and Danaoban Lake of Inner Mongolia in China were also identified for the first time as wintering and summering sites, respectively. We also found that human population density and GPP were crucial determinants of stopover duration in the Eastern and Western Chinese swan populations both in spring and in autumn. Our findings provide basic data for future research on mute swans in East Asia and will contribute to conservation action plan development through current conservation status evaluations of important summering, wintering and stopover sites along the migration routes of mute swans.

Behavioural Monitoring and Threats Assessment of Ibisbill (Ibidorhynchastruthersii) in the Wintering Site, East Rapti River, Hetauda, Nepal

Behavioural Monitoring and Threats Assessment of Ibisbill (Ibidorhynchastruthersii) in the Wintering Site, East Rapti River, Hetauda, Nepal

It takes two to Tango: Plant height and nutrient level determine the diet selection of wintering geese in Poyang Lake, a Ramsar wetland

In Poyang Lake, the largest and one of the most important wintering sites in the East Asian-Australasian Flyway, Carex (Carex cinerascens Kük) meadows provide the primary food source for the wintering geese. However, due to intensified river regulation and more frequent extreme climatic events such as drought, observational evidence suggests that the synchrony of geese migration and Carex phenology could not be maintained without human interventions, imposing a great risk of food shortage during the wintering period. Consequently, the current conservation priority in this Ramsar site is shifted to wet meadow improvement to ensure optimal food quality. Understanding the food preferences of wintering geese is the key for effective wet meadow management. As the growth stage and nutrient level of food plants are the decisive factors influencing the diet selection of herbivores, in this study, we sampled the preferred food items by tracking the foraging paths of the Greater White-fronted Goose (n = 84) and Bean Goose (n = 34) to quantify the “foraging window” in terms of plant height,protein level, and energy content. Further, we established relationships between the above three variables of Carex based on in-situ measurements. The results show that the geese prefer plants with height ranging from 2.4 to 25.0 cm, with protein content from 13.9 to 25.2 %, and energy content from 1440.0 to 1813.6 KJ/100 g. While plant energy content increases with height, the height-protein level relationship is negative. The opposite growth curves signify a conservation challenge to maintain the delicate balance between the quantity and quality requirements of wintering geese. Carex meadow management, such as mowing, should focus on optimizing the timing of action to maximize energy supply while maintaining the right protein level for the long-term fitness, reproduction and survival of the birds.