One of the most widespread passerines breeding in Europe, the willow warbler Phylloscopus trochilus, has declined considerably. Here, we analyse the production of offspring in the southern subspecies of willow warbler at Gotland, Sweden, by utilizing data on post-juvenile moult of first-year birds from standardized ringing during 1990–2024, and comparing our findings with meteorological data. The number of first-year birds ringed in postjuvenile moult stage 0–4, which means that they are hatched in the vicinity, varied greatly, with an annual average of 317 (range 50–591) individuals and a significant negative trend over time. During 1990–2006, the number was relatively stable at 431 ± 85 (SD), followed by decreasing numbers and higher variation 2007–2024. Compared to 1990–2006, the number of ringed first-year willow warblers in moult stage 0–4 decreased by 74 % (112 ± 44) from 2016 onwards, and was negatively related to temperature during the incubation and the nestling period, but not during the fledgling period. There was no significant relationship between precipitation and the number of birds ringed. We discuss the results with respect to increased temperature during breeding, following climate change, involving negative effects on offspring productivity.
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.
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.
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.
