Agricultural intensification has contributed to biodiversity decline across Europe, yet traditional landscapes in Central and Eastern Europe, still dominated by relatively extensive farmland practices, remain important for many species. We studied foraging habitat use of White Storks (Ciconia ciconia) in one of the largest breeding colonies in Poland, located in a region characterized by extensive agricultural management. Using generalized linear mixed models, we examined how habitat type, mowing frequency, and distance from the colony affected the number of foraging individuals and their mean foraging time. Pastures, intensively managed grasslands, arable land, and small ponds had significant positive effects on the number of foraging individuals, whereas wastelands and increasing distance from the breeding colony had negative effects. Mowing frequency significantly influenced stork abundance in a non-linear manner, with the highest numbers recorded in twice-mown areas. In contrast, mean foraging time was not affected by habitat type or mowing frequency but was consistently and positively related to distance from the breeding colony across all models, indicating longer foraging bouts at more distant sites. Both the number of individuals and mean foraging time increased significantly over the breeding season. Our findings confirm the key importance of pastures as foraging habitats for White Storks and highlight the role of heterogeneous landscape structure and temporally and spatially diversified management. These findings have practical implications for agri-environmental schemes aimed at supporting farmland biodiversity.
The rapid green transition has accelerated wind-energy development, increasing threats to large soaring raptors. Understanding key elements of movement behaviour—such as spatiotemporal variation in territory use that influences, for example, collision risk—is essential for reliable environmental impact assessment (EIA). We studied territorial movements of GPS-tagged Golden Eagles (Aquila chrysaetos; 11 males, 7 females) in central and northern Finland during 2011–2022. Using generalized linear mixed models, we evaluated the effects of sex, breeding status, month (March–October), and latitude on daily flight time and breeding-season territory size (core area and home range; 50% and 95% MCP, respectively). Flight time showed strong seasonality driven by sex and breeding status. Breeding males flew longer during incubation and the nestling period, whereas breeding females flew significantly less. Non-breeding birds showed weaker seasonal variation, consistent with the absence of parental care duties. Neither core-area size nor home-range size showed a statistically significant association with latitude, although MCP95 tended to decrease towards northern latitudes. Non-breeding females also tended to occupy larger home ranges than breeding females, whereas no corresponding difference was observed in males. Core areas tended to be larger in non-breeding than in breeding birds, and this pattern was most pronounced in females. Because flight activity and territory size depend strongly on individual characteristics and spatial context, we recommend that EIA monitoring covers multiple years, and that wind-energy guidance (e.g., buffer distances) is set conservatively based on individuals with the highest flight activity and/or the largest territories.
Irruptive migration is a form of partial migration, where the part of the population that migrates varies significantly between years. The intensity of irruptions has been explained by variation in food availability, breeding success and breeding population size. We investigated factors affecting the irruptions by northern nutcrackers Nucifraga caryocatactes (hereafter nutcrackers) in northern Europe. We used long-term monitoring data on nutcrackers autumn migrating in SW Finland (Hanko) and SW Sweden (Falsterbo), the age ratio of nutcrackers in Finland, breeding population size estimates in Sweden, the annual pollen abundance variation of hazel nuts Corylus avellana in Finland and Sweden and annual nut crop size variation in SW Finland. Two subspecies of nutcrackers occur in the area: southern breeding birds belong to the nominate subspecies caryocatactes, whereas individuals of the macrorhynchos subspecies breed further north but also occur in irruptions from the east (Russia). The ringing numbers of the nominate subspecies at Hanko were negatively correlated with the nut crop size, but this connection was not found in macrorhynchos. The annual autumn total nutcracker migration numbers in Hanko and Falsterbo were negatively connected with hazel nut crop size and also hazel pollen abundance in Hanko. Proportion of young was positively connected with migration intensity in Hanko. The Swedish adult breeding population size did not show any connection with the migration numbers in Falsterbo. The role of the nut crop size was clearly stronger than the age ratio indicating that the lack of food is the key driver of the irruptions.
As part of migration, birds interrupt their flight to rest and replenish energy at stopovers. In this study, we investigated various factors (weather, date of ringing, tape-luring method) affecting the proportion of recaptured Eurasian Blackcaps during autumn migration (August, 14 to November, 5) and factors (weather, sex, age, date of ringing, tape-luring method) affecting their stopover duration. We analysed a 20-year dataset (2006–2025) from Drienovec Bird Ringing Station (SE Slovakia) situated on the SE European migration route of birds. Among 66,673 ringed Eurasian Blackcaps 9.39% were recaptured within the same season. The proportion of recaptured individuals was significantly lower with the use of night time tape-luring than with the use of day playback and with no playback, respectively. Recaptures were also fewer later in the season, and on days with mild wind and clear sky without low-level clouds. The minimum stopover duration of recaptured individuals lasted from 2 to 75 days. Median was 5 days. Females stayed significantly, about one day, longer than males. Stopover duration decreased with the later date of ringing. Furthermore, the interaction between age and tape-luring method was significant. The stopover was significantly longer in adults than in juveniles when using the night playback. Eurasian Blackcaps showed longer stopovers during days colder than average, with strong wind or precipitation. Also, with high air pressure and low cloudiness, indicating good weather, stopover duration increased. Our data support not only the influence of factors such as weather, date of ringing and sex on the stopover ecology of Eurasian Blackcaps, but also document the effects of tape-luring.
The costs and benefits of post-fledging dispersal give rise to diverse dispersal strategies in birds; however, the underlying patterns and mechanisms remain poorly understood in many species. We investigated natal dispersal and migration in juvenile Common Kingfishers (Alcedo atthis) originating from Czech and Slovak populations. Natal dispersal was examined by monitoring two breeding populations between 2014 and 2018. Of the 1,911 nestlings ringed during this period, 19 juveniles were subsequently recaptured, yielding a recovery rate of 0.36%. Most individuals (74%) settled within 20 km of their natal sites (median dispersal distance = 10.5 km), with no significant differences observed between populations or sexes. To assess large-scale migratory patterns, we supplemented our field data with ringing recoveries obtained from the Czech and Slovak Bird Ringing Centres (n = 264). In the last 50 years, migratory individuals (62%) slightly outnumbered resident birds (38%). The proportion of migrants and residents differed significantly among decades, with migrants increasingly predominating over time. Migration distance was significantly associated with fledging date: individuals fledging earlier in the breeding season (May–July) tended to migrate longer distances than those fledging later (August–September). Clear geographical variation in migratory direction was also detected. Juveniles from Bohemian and Slovak populations predominantly migrated southwest, whereas birds from Moravia generally migrated southward. Most kingfishers originating from Bohemia wintered in Western Europe, while individuals from Moravia and Slovakia were more likely to overwinter in southern Italy, the Balkans, and North Africa. It appears that juvenile Common Kingfishers exhibit a flexible migratory strategy shaped by both breeding phenology, which affects migration distance, and location of breeding sites determining migratory direction.
