For loons (Gaviidae), there is good evidence of long-term displacement around offshore wind farms on wintering grounds, but studies of any impact on either Red-throated Loon Gavia stellata or Black-throated Loon Gavia arctica from land-based wind turbines are scarce. Current recommendations, based on best available knowledge, are not to locate wind turbines closer than 1 km from breeding sites, and for Red-throated Loon also to avoid locating turbines on the flight routes between breeding pools and foraging waters. These recommendations sometimes necessitate substantial modifications during the planning of a wind farm. To study their relevance, pairwise comparisons of the occupation of breeding lakes and breeding success before and after the start of operation were done. For Red-throated Loon, impaired breeding performance was indicated, and ideally the recommendations should be extended not to locate wind turbines within 2 km from breeding sites. For Black-throated Loon, there were no indications of impact, but the results are not entirely conclusive as they rest on data from a small number of breeding sites. Thus, a cautionary approach should be applied. We need further knowledge about impact related future large-scale wind farms and long-term impact over at least one generation after start of operation.

This paper aims to reflect the population dynamics of Black Redstart Phoenicurus ochruros during the 50-year period 1975–2024 in western Sweden. The results show a strong decrease in population size, averaging 70 %. Weedy areas with broken buildings, important for foraging and nesting, were widespread within the study areas during the 1980s. Extensive construction development has subsequently taken place in these areas. Changes in the breeding environments are likely the main reason behind the population decrease. In the study areas of Gothenburg, Varberg and Falkenberg, the habitat loss of breeding territories amounts to 92%. Additionally, there are likely several unknown factors contributing to the decrease in Black Redstart numbers in western Sweden, for example large-scale faunal shifts and climate change. The importance of source areas for the addition of individuals to marginal populations is well-known and could affect both immigration and expansion, as well as the decrease and disappearance of a species. Interspecific competition with Common Redstarts Phoenicurus phoenicurus is another factor that may be important. If the population trend reported here continues, there is an obvious risk that the Black Redstart will disappear as a western Swedish breeding species in the not-too-distant future.

THE PEREGRINE FALCON populations across Europe and North America were almost exterminated in the 1970s; in Sweden, only 15 pairs were known by 1975. One of the main causes was reduced productivity due to eggshell thinning attributed to the widespread use of organochlorine pesticides. This study analysed eggshell thickness in samples collected across Sweden between 1964 and 2023, and compared with eggs from 1865-1945. The results indicate very thin shells in the 1960s to 1980s when eggshells were on average -16% of normal thickness, with records of -29%. Since then, the average thickness steadily increased and, alongside, the Peregrine population has recovered. While differences in shell thickness and recovery rates between northern and southern Sweden were observed, they were not statistically significant. In 2020s the average eggshell thickness is still -6% below normal which is within safe levels. However, because new substances with the potential to affect eggshell thickness are increasing in the environment, it is worthwhile to continue to collect and measure eggshells as a simple and low-cost way to monitor one of the effects of environmental contaminants. The Peregrine remains an important indicator for unintended side effects of chemical substances released into the environment.

Bird species in boreal forests that utilise seed crops from masting trees face large temporal and spatial variation in food availability. Seed crop size is therefore expected to influence breeding population size, migration, and wintering. We analyse ≤36-year time series of Eurasian Siskin Spinus spinus numbers in Sweden in relation to seed crop sizes of Norway spruce Picea abies, Scots pine Pinus sylvestris, birch Betula spp. and alder Alnus spp. Breeding numbers were somewhat positively associated with spruce, birch, and alder seed crop sizes, but peak breeding numbers sometimes also coincided with small crop sizes. Migration was not strongly related to seed crop sizes, but positively associated with breeding population size. Wintering numbers were strongly positively associated with spruce, birch, and alder seed crop sizes. Pine did not affect any Siskin numbers. This suggests that at large spatial and temporal scales, spruce seeds are less important for Siskin breeding than previously thought. Nevertheless, spruce, birch and alder may all have some influence on breeding and were positively associated with wintering numbers, while migration appears to be a density-dependent process rather than a response to lack of food. The results provide a unique insight into how multiple seed crops affect a seed-eating bird.

The typically resident Coal Tit Periparus ater, which is widespread in Eurasia, may migrate from breeding sites in large numbers in certain environmental conditions. I used observations from 2005–2023 in a lowland area of south-eastern Hungary to detect irruptive movements of the species. In total, I observed Coal Tits on 258 different days. In some years, they were absent, while in others they occurred in higher numbers. Comparing my data with literature suggests that the birds occurring in south-eastern Hungary are not of the same origin as the birds migrating more regularly through western Hungary. The birds in the study area instead likely originate from the mountainous areas of Romania or the northern Great Hungarian Plain. I found no correlation between the annual numbers of occurrences in south-eastern Hungary and northern Europe, so northern birds likely do not normally enter the Carpathian Basin. However, in 2018, Coal Tits were present in higher numbers in the Great Hungarian Plain as well as in northern Europe, so it is possible that some northern individuals may appear in eastern Hungary during large northern invasions.

The blowfly Trypocalliphora braueri is a subcutaneous parasite infesting nestlings. We investigated the occurrence of blowfly larvae in Willow Warbler Phylloscopus trochilus nestlings on the Kola Peninsula, Russia, in 2023–2024. The infestation rate was 46.9% of nests and 37.9% of chicks. The highest infestation rates were observed during a season with a late beginning of bird breeding and an unusually warm summer. In the infested nests, 86.2% (28.6–100%) of nestlings contained 1–11 larvae. Chicks with many larvae or with vital organ damage died. Nestling survival in the infested nests decreased by 15.4% compared to that in uninfected nests, but these differences were not statistically significant. We also found no significant differences in infestation rates between areas with varying levels of anthropogenic pressure.

The breeding grounds of the North Atlantic population of Sandwich Tern Thalasseus sandvicensis range along the coasts of western Europe and in the Baltic Sea: predominantly in the Netherlands, UK, France, Germany, and Denmark, with a smaller fraction of the population breeding in southern Sweden. This population has fluctuated strongly in size in recent decades due to human activities, pollution, changing availability of food, and outbreaks of highly pathogenic avian influenza. To evaluate whether management actions to further protect the species are needed in Sweden, better knowledge about the recent development of the breeding population is required. We found that the total number of breeding pairs in Sweden between 2007 and 2014 fluctuated between c. 390 and c. 570 pairs. Later, the number increased markedly from c. 630 pairs in 2015 to c. 1,830 pairs in 2021. In 2022 and 2023, the number decreased partly due to avian influenza outbreaks and c. 1,540 pairs bred in 2023. Most pairs bred in the provinces of Blekinge, Gotland, and Skåne. The four largest colonies hosted c. 55% of the cumulative number of breeding pairs between 2007 and 2023. This aggregated distribution makes the species vulnerable to various threats.

The breeding success of a nest-box breeding population of Pied Flycatcher Ficedula hypoleuca in subalpine birch forest in Swedish Lapland was studied over 55 years, with emphasis on the impact of small mustelids and ambient temperature during egg laying, incubation, and brood care. The proportion of nests predated was used as an index for mustelid abundance. Breeding failures were either total, due to breeding interruptions, or partial due to partial hatching failure or nestling death. Overall, mustelid abundance explained the rate of breeding interruptions at any breeding phase, but not when seasons with exceptional (>10%) predation rates were excluded. Variation in the rate of partial failure was unrelated to mustelid abundance. Climatic conditions affected clutch size, rate of breeding interruption, and partial loss of clutches or broods, with particularly pronounced effects during the incubation period. The mustelid abundance and weather conditions also influenced rates of nest-box occupation in subsequent breeding seasons, and the next-box population dynamics covaried with surrounding populations.

Knowledge of migration patterns plays an essential role for understanding spatiotemporal distribution of birds. Here we used >15,000 sightings of 1,473 colour-ringed Common Cranes Grus grus to study migration patterns of birds breeding in five regions along a longitudinal gradient of Fennoscandia. Our results confirm that Fennoscandian cranes mainly use either a Western European flyway (W-flyway), to winter mainly in France or Spain, or a Central European flyway (C-flyway), to winter in Hungary or Israel. Finnish cranes showed the greatest variation in migration patterns in terms of distance and direction and only Finnish cranes were recovered in Africa. Many of the Finnish cranes, starting along C-flyway change to the W-flyway and winter in SW Europe or NW Africa. On the other hand, the Scandinavian cranes are rarely observed along the C-flyway. However, substantial numbers of cranes from NE Sweden cross the Baltic Sea and migrate via Finland but then follow the W-flyway from Germany and southwards, especially during autumn. These results can be used for conservation and management, e.g. to coordinate monitoring. They are also relevant for land use planning, e.g. to avoid windfarms at sites important for migrating soaring birds while crossing seas, so-called ‘thermal bottleneck sites’.