Testing for Geographic Variation in Survival of Spectacled Eider (Somateria fischeri) Populations in Chukotka, Russia and the Yukon-Kuskokwim Delta, Alaska

Information on variation in survival among geographically distinct breeding populations can produce valuable insights about the population dynamics of a species. The Yukon-Kuskokwim Delta sub-population of Spectacled Eiders in Alaska decreased precipitously between the 1950s and 1990s. Causes for this decline are unknown but may be attributed to low female survival due to predation and lead exposure on the breeding grounds. From 2014 to 2015, we compared annual survival probabilities of Spectacled Eiders on Kigigak Island in the Yukon-Kuskokwim Delta, Alaska, and Ayopechan Island in the Chaun Delta, Chukotka, where similar field protocols were implemented. A Cormack-Jolly-Seber maximum likelihood approach was used to estimate apparent survival (φ) and recapture probability (p) from mark-resight data. We tested a) whether Russian and Alaskan sub-populations differed in their survival rates, b) whether survival varied annually, and c) whether survival followed an increasing or decreasing trend over time at either site. We found no evidence for differing survival between the two breeding areas when mean survival across years was compared, and we did not find strong evidence for a linear trend in survival over time at either site. Furthermore, our data supported models with annually varying survival at Kigigak Island and constant survival at Ayopechan Island. Sample size constraints precluded estimates of annual survival at Ayopechan Island. Our finding of no difference in mean survival between sites lends support to the idea that survival may be a function of conditions on the wintering grounds.Les données en matière de variations de survie chez des populations nicheuses géographiquement distinctes peuvent donner un précieux aperçu de la dynamique des populations d’une espèce. La sous-population d’eiders à lunettes du delta Yukon-Kuskokwim, en Alaska, a chuté abruptement entre les années 1950 et les années 1990. Nul ne connaît les causes de ce déclin, mais elles pourraient être attribuables au faible taux de survie des femelles en lien avec la prédation et l’exposition au plomb dans les aires de reproduction. De 2014 à 2015, nous avons comparé les probabilités de survie annuelle des eiders à lunettes sur l’île Kigigak, dans le delta Yukon-Kuskokwim, en Alaska, et sur l’île Ayopechan, dans le delta Chaun, au Tchoukotcha, où des protocoles d’étude similaires sur le terrain ont été adoptés. La méthode du maximum de vraisemblance Cormack-Jolly-Seber a servi à estimer la survie apparente (φ) et la probabilité de recapture (p) à partir de données de marquage et de relocalisation. Nous avons tenté de déterminer a) si les sous-populations de la Russie et de l’Alaska avaient des taux de survie différents, b) si les taux de survie variaient d’une année à l’autre et c) si le taux de survie affichait une tendance à la hausse ou à la baisse au fil des ans à l’un ou l’autre des sites. Nous n’avons trouvé aucune preuve justifiant le taux de survie différent aux deux aires de reproduction au moyen de la comparaison des moyennes de survie au fil des ans, et nous n’avons pas trouvé de preuve importante permettant de déceler une tendance linéaire au fil des ans en matière de survie à l’un ou l’autre des deux sites. De plus, nos données ont permis d’étayer des modèles ayant des taux de survie annuels variables à l’île Kigigak et des taux de survie constants à l’île Ayopechan. Des contraintes en matière de taille d’échantillons ont empêché de faire l’estimation des taux de survie annuels à l’île Ayopechan. Le fait que nous n’ayons pas trouvé de différence entre les moyennes de survie des deux sites soutient l’idée selon laquelle la survie peut être tributaire des conditions des aires d’hivernage.Данные об изменении выживаемости в географически обособленных гнездовых популяциях позволяют понять тенденции динамики популяций рассматриваемого вида. В период с 1950-х по 1990-е гг. наблюдалось резкое снижение численности гнездовой популяции очковой гаги в дельте рр. Юкон-Кускоквим, предположительно обусловленное низкой выживаемостью взрослых самок из-за сильного пресса хищников и отравления птиц свинцом в районах гнездования. Мы сравнивали показатели ежегодной выживаемости взрослых самок очковой гаги на о. Кигигак, дельта рр. Юкон-Кускоквим, Аляска, США и на о. Айопечан, дельта рр. Чаун-Пучевеем, Чукотка, Россия. Идентичные полевые протоколы были разработаны и применены в обоих районах исследования. Метод максимального правдоподобия Кормака-Джоли-Себера использовался для оценки ежегодной выживаемости (φ) и вероятности обнаружения (p) птиц по данным повторных отловов. Мы проверяли: а) существование статистически значимых различий в выживаемости самок очковой гаги чукотской и аляскинской популяций в период с 2002 по 2015 гг.; б) межгодовые колебания ежегодной выживаемости; в) наличие тенденций повышения или понижения выживаемости с течением времени в каждой из популяций. Мы не выявили статистически достоверных различий в выживаемости самок из двух районов гнездования, а так же не обнаружили тренда выживаемости со временем ни в одной из популяций. Данные, которыми мы располагаем, позволили оценить ежегодную выживаемость самок на о. Кигигак и, по причине недостатка данных, среднюю межгодовую выживаемость самок на о. Айопечан. Наши выводы о том, что выживаемость самок одинакова в обеих популяциях, позволяют предположить, что на выживаемость очковых гаг в меньшей степени влияют условия гнездовых территорий, чем комплексные условия акватории зимовки

The effect of climate change on avian offspring production: A global meta-analysis

Climate change affects timing of reproduction in many bird species, but few studies have investigated its influence on annual reproductive output. Here, we assess changes in the annual production of young by female breeders in 201 populations of 104 bird species (N = 745,962 clutches) covering all continents between 1970 and 2019. Overall, average offspring production has declined in recent decades, but considerable differences were found among species and populations. A total of 56.7% of populations showed a declining trend in offspring production (significant in 17.4%), whereas 43.3% exhibited an increase (significant in 10.4%). The results show that climatic changes affect offspring production through compounded effects on ecological and life history traits of species. Migratory and larger-bodied species experienced reduced offspring production with increasing temperatures during the chick-rearing period, whereas smaller-bodied, sedentary species tended to produce more offspring. Likewise, multi-brooded species showed increased breeding success with increasing temperatures, whereas rising temperatures were unrelated to repro- ductive success in single-brooded species. Our study suggests that rapid declines in size of bird populations reported by many studies from different parts of the world are driven only to a small degree by changes in the production of young

Use of geolocators reveals previously unknown Chinese and Korean scaly-sided merganser wintering sites

We determined, for the first time, individual linkages between breeding areas of nesting female scaly-sided mergansers Mergus squamatus in the Russian Far East and their previously unknown wintering grounds in coastal Korea and inland China. Geolocators were deployed on nesting females caught and recaptured on nests along a 40-km stretch of the Kievka River. Mean positions for brood-rearing females during the summer were on average within 61.9 km of the nest site, suggesting reasonable device accuracy for subsequent location of winter quarters. Geolocation data showed that most birds wintered on freshwater habitats throughout mainland China, straddling an area 830 km E−W and 1100 km N−S. Most wintered in discrete mountainous areas with extensive timber cover, large rivers and low human population density. Three birds tracked in more than one season returned to within 25−150 km of previous wintering areas in successive years, suggesting winter fidelity to catchments if not specific sites. A single female from the adjacent Avvakumovka catchment wintered on saltwater in Korea, at least 1300 km east of Chinese wintering birds. Most sea duck species (Tribe Mergini) form pairs away from breeding areas, suggesting that this high level of winter dispersal amongst close-nesting females is a potential mechanism to maintain gene flow in this threatened species that has specialist habitat requirements. Hence, female scaly-sided mergansers disperse widely from breeding areas, but show fidelity to nesting areas and winter quarter

Flyways and migratory behaviour of the Vega gull (Larus vegae), a little-known Arctic endemic.

Large gulls are generalist predators that play an important role in Arctic food webs. Describing the migratory patterns and phenology of these predators is essential to understanding how Arctic ecosystems function. However, from all six large Arctic gull taxa, including three long-distance migrants, to date seasonal movements have been studied only in three and with small sample sizes. To document the flyways and migratory behaviour of the Vega gull, a widespread but little-studied Siberian migrant, we monitored 28 individuals with GPS loggers over a mean period of 383 days. Birds used similar routes in spring and autumn, preferring coastal to inland or offshore routes, and travelled 4000-5500 km between their breeding (Siberia) and wintering grounds (mainly the Republic of Korea and Japan). Spring migration mainly occurred in May, and was twice as fast and more synchronized among individuals than autumn migration. Migration bouts mainly occurred during the day and twilight, but rates of travel were always higher during the few night flights. Flight altitudes were nearly always higher during migration bouts than during other bouts, and lower during twilight than during night or day. Altitudes above 2000m were recorded during migrations, when birds made non-stop inland flights over mountain ranges and vast stretches of the boreal forest. Individuals showed high inter-annual consistency in their movements in winter and summer, indicating strong site fidelity to their breeding and wintering sites. Within-individual variation was similar in spring and autumn, but between individual variation was higher in autumn than in spring. Compared to previous studies, our results suggest that the timing of spring migration in large Arctic gulls is likely constrained by snowmelt at breeding grounds, while the duration of migration windows could be related to the proportion of inland versus coastal habitats found along their flyways ('fly-and-forage' strategy). Ongoing environmental changes are hence likely in short term to alter the timing of their migration, and in long term possibly affect the duration if e.g. the resource availability along the route changes in the future

Population trends and migration routes of the East Asian Bean Goose Anser fabalis middendorffii and A. f. serrirostris

Our ability to define the population status, migration routes and seasonal distribution of Bean Geese Anser fabalis throughout the annual cycle in East Asia is severely compromised by the presence of two subspecies (Eastern Taiga Bean Goose A. f. middendorffii and Eastern Tundra Bean Goose A. f. serrirostris), which are difficult to differentiate in the field. In this analysis, using tracking data from telemetry-tagged geese, count survey data and expert knowledge, we attempt to update existing knowledge of the ranges covered by both subspecies of Bean Goose in East Asia. We suggest that, in summer, the Eastern Tundra Bean Goose ranges from the Taimyr Peninsula in the west to the Anadyr River in the east. Taiga Bean Geese breed further south in the taiga zone, and results indicate that they occur in north-western Mongolia, Yakutia and the Kamchatka Peninsula during the summer months. The winter distribution of both subspecies extends through China, Japan and South Korea. Tracking data from 154 individuals revealed a major overlap in the migration routes of Tundra Bean Geese wintering in China, South Korea and Japan, but discrete flyways for Taiga Bean Geese wintering in different regions. Long-term ground surveys carried out in the wintering range showed that numbers of Bean Geese in China and South Korea have increased significantly, to number 253,100 and 88,300 individuals respectively, of which roughly 10% are considered to be Taiga Bean Geese, about which subspecies we need to know more. Numbers of Japanese-wintering Bean Geese are slowly rising, currently numbering c. 10,300 (c. 900 Tundra Bean Geese and c. 9,400 Taiga Bean Geese). On the basis of these national and flyway estimates, derived from counts over the last five years, we identify new key wintering sites for the species in East Asia. Distributional changes at sites in China showed that wintering Bean Geese (most likely of the Tundra form) have become more widespread and numerous in the Yangtze River floodplain since the early 2000s. We argue for future strengthening of international cooperation to continue tracking and monitoring of Bean Geese, to provide a sound scientific basis for the effective management and protection of the flyway populations of both Bean Goose subspecies throughout East Asia

The effect of climate change on avian offspring production: A global meta-analysis

Climate change affects timing of reproduction in many bird species, but few stud-ies have investigated its influence on annual reproductive output. Here, we assess changes in the annual production of young by female breeders in 201 populations of 104 bird species (N = 745,962 clutches) covering all continents between 1970 and 2019. Overall, average offspring production has declined in recent decades, but considerable differences were found among species and populations. A total of 56.7% of populations showed a declining trend in offspring production (significant in 17.4%), whereas 43.3% exhibited an increase (significant in 10.4%). The results show that climatic changes affect offspring production through compounded effects on ecological and life history traits of species. Migratory and larger-bodied species experienced reduced offspring production with increasing temperatures during the chick-rearing period, whereas smaller-bodied, sedentary species tended to produce more offspring. Likewise, multi-brooded species showed increased breeding success with increasing temperatures, whereas rising temperatures were unrelated to repro-ductive success in single-brooded species. Our study suggests that rapid declines in size of bird populations reported by many studies from different parts of the world are driven only to a small degree by changes in the production of young

Two distinct flyways with different population trends of Bewick's Swan Cygnus columbianus bewickii in East Asia

Two of the most fundamental ecological questions about any species relate to where they occur and in what abundance. Here, we combine GPS telemetry data, survey data and expert knowledge for the first time to define two distinct flyways (the East Asian Continental and West Pacific flyways), migration routes and abundance for the Eastern population of Bewick’s Swan Cygnus columbianus bewickii. The Eastern population is the largest flyway population, supporting c. 77% of Bewick’s Swan numbers globally. GPS telemetry data showed that birds breeding in the Russian arctic from the Yamal Peninsula to c. 140°E (including the Lena and Yana Deltas), winter in the middle and lower reaches of the Yangtze River in China (which we label the “East Asian Continental flyway”). Bewick’s Swans breeding from the Indigirka River east to the Koluchin Bay winter in Japan, mostly in Niigata, Yamagata and Ishikawa Prefectures (the “West Pacific flyway”). There was no overlap in migration routes used by tagged individuals from the two flyways. Counts of Bewick’s Swans in the East Asian Continental flyway during the 21st century have shown wide between-year variations, reflecting incomplete coverage in earlier years. Bewick’s Swans in this flyway currently numbers c. 65,000 birds based on extensive wintering survey coverage, compared to c. 81,000 in the early 2000s, based on less complete coverage. Chinese-wintering swans now concentrate mainly (c. 80%) at Poyang Lake in Jiangxi Province and Hubei Lakes (mostly in Longgan Lake), compared to a more widespread distribution both within Poyang and throughout the Auhui Lakes in 2004 and 2005. In contrast, Bewick’s Swans of the West Pacific flyway now numbers c. 40,000, compared to just 542 in 1970. This population has shown no significant overall change since 2004, when it numbered c. 45,000 birds. Small numbers within this population probably also winter in South Korea. These results provide our first basic understanding of the winter distribution of Chinese- and Japanese-wintering Bewick’s Swans in relation to their breeding areas, confirming the need to coordinate future research and monitoring in the two flyways, as well as the need for more information on swans wintering in South Korea

Documenting lemming population change in the Arctic: Can we detect trends?

Lemmings are a key component of tundra food webs and changes in their dynamics can affect the whole ecosystem. We present a comprehensive overview of lemming monitoring and research activities, and assess recent trends in lemming abundance across the circumpolar Arctic. Since 2000, lemmings have been monitored at 49 sites of which 38 are still active. The sites were not evenly distributed with notably Russia and high Arctic Canada underrepresented. Abundance was monitored at all sites, but methods and levels of precision varied greatly. Other important attributes such as health, genetic diversity and potential drivers of population change, were often not monitored. There was no evidence that lemming populations were decreasing in general, although a negative trend was detected for low arctic populations sympatric with voles. To keep the pace of arctic change, we recommend maintaining long-term programmes while harmonizing methods, improving spatial coverage and integrating an ecosystem perspective