Weather effects on bird migration are well-studied among Passerines moving from Europe to Africa or within the American flyway systems. However, little is known about the weather impact on songbirds migrating along the East Asian flyway. Our study aims to describe the effects of various weather elements on the migration of four species of leaf warblers by using bird ringing data from a stopover site in Far East Russia. We determined the migration periods for each species and included maximum temperature, precipitation, air pressure, wind speed and wind direction in general linearized mixed models to predict the number of migrating birds. We found strong impacts of weather variables on the number of trapped warblers during spring and autumn migration. Preferred or avoided weather conditions were similar among the studied species. All species seem to migrate preferably during warm, calm days without precipitation. A positive effect of tail winds was only confirmed in autumn, but in spring, most birds were trapped during crosswinds (eastern or western winds). The studied species might exhibit a loop migration, leading to a more longitudinal (from east to west) migration pattern in our study area during spring. Relationships between weather variables and the number of migrating individuals were much stronger during autumn. We argue that birds during spring migration would continue migration under sub-optimal conditions, as a result of strong competition to arrive earliest on their breeding grounds.

Over the past decades, spring temperatures have increased in temperate regions, which resulted in birds arriving earlier in spring. Nonetheless, the timing of some species’ spring migration relies on endogenous rhythms that are not affected by climate change. In this study, we analysed changes in the spring arrival dates of 36 bird species over two periods in 22 towns and villages in Southeast Hungary and West Romania. The first period covered the national spring migration counts between 1894 and 1926, while the second period took place between 2005 and 2019 and is based on our recent observation data. Our results show, that the average spring arrival dates of most long-distance migrant species have not changed significantly over the past 100 years. In contrast, in cases of medium and short-distance migrants, most species arrive earlier recently than in the past. This may be caused by the fact, that the migration habit of long-distance migrants is characterized by strong genetic determinants, so they can not react as quickly to the warmer spring weather in Europe as the medium and short-distance migrants. However, in cases of some long-distance migrants, the timing of spring migration changed due to the drying of wintering grounds.

We examined the autumn migration phenology of nine Siberian breeding songbirds: Thick-billed Warbler (Iduna aedon), Black-browed Reed Warbler (Acrocephalus bistrigiceps), Pallas’s Grasshopper Warbler (Locustella certhiola), Lanceolated Warbler (L. lanceolata), Yellow-browed Warbler (Phylloscopus inornatus), Arctic Warbler (Ph. borealis), Dusky Warbler (Ph. fuscatus), Radde’s Warbler (Ph. schwarzi), Two-barred Warbler (Ph. plumbeitarsus) and compared the migration dynamic characteristics with their European occurrence time. The study was carried out within the Amur Bird Project in the Russian Far East along the river Amur at Muraviovka Park between 2011 and 2014. The birds were caught with mistnets and ringed with individually numbered rings. For the characterization of the migration, we used timing, the intervals and the peaks of the migration, the percentage of the recaptures and the average time between the first and the last captures. The timing of migration in the studied species differed in the timing, the intervals (30-67 days) and the migration peaks (14 August - 17 September). Considering the size and location of the distribution area, the timing and annual patterns of European occurrences, it is likely that most individuals of Thick-billed Warbler, Pallas’s Grasshopper Warbler, Dusky Warbler, Radde’s Warbler and Two-barred Warbler get to Europe due to the impact of Siberian cyclones. In case of Yellow- browed Warblers, other factors (reverse migration, weather conditions, dispersal movements) may also play a role. Because of their Scandinavian breeding populations, dispersion movement is the most likely reason for vagrants of Arctic Warbler and Lanceolated Warbler. The distribution of the Black-browed Reed Warbler is limited to the eastern edge of the continent, and therefore this species has no European record to date.

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Knowledge of the routes and habitat use of Siberian songbird species during migration is very limited. The goal of our study was to describe the autumnal habitat use of seven Siberian warbler species in the genera Phylloscopus, Acrocephalus, Iduna and Locustella in Far Eastern Russia. A total of 2283 individuals were trapped in mist nets placed within different habitat types between 2012 and 2014 as part of the Amur Bird Project at Muraviovka Park in Far Eastern Russia. We studied the effect of habitat type and vegetation height on the occurrence of each species, and compared our results to published information on habitat use on the breeding grounds. Our results demonstrate that most species exhibit species-specific preferences for habitat type, and that these stopover habitats were similar to habitats used on the breeding grounds.

The timing of annual events in migratory species is determined by the position of breeding and wintering grounds, length of the breeding season, the occurrence of their preferred diet or the timing of moult in birds. Previous studies found significant differences in the migration phenology of AsianPhylloscopuswarbler species, a group of long-distance migratory passerines. However, the factors that influence the observed differences in migration phenology have not been studied yet. Here, we analyze the effect of the above-mentioned factors on the migration timing of sevenPhylloscopusspecies at a stopover site in the Russian Far East. We found that spring migration phenology was best explained by moult strategy and the preferred prey size, while autumn migration phenology was linked to the southernmost wintering latitude of the species. Interspecific differences in migration timing were much higher in autumn than in spring. The duration of the species-specific migration periods was also longer in autumn than in spring, most likely caused by higher competition during spring to arrive early at the breeding grounds. Our results contribute to the understanding of migration ecology in songbirds moving along the little-studied East Asian flyway.