Abstract The critically endangered Rüppell’s Vulture ( Gyps rueppelli ), originally from sub-Saharan Africa, has recently begun to establish itself in Europe, specifically in the Iberian Peninsula. This study focuses on understanding the spatial ecology of Rüppell’s Vultures during the breeding season, analyzing movement patterns and home-range sizes of three individuals tagged with GPS in southern Spain. The results show significant differences in home-range sizes between adult and immature vultures, with the immature individual exhibiting larger ranges and exploratory behavior, while adults, particularly during breeding, displayed more localized movements. The integration of Rüppell’s Vultures with Griffon Vultures ( Gyps fulvus ), including hybrid breeding attempts, raises conservation concerns regarding potential genetic amalgamation. The study highlights the need for transboundary conservation strategies, as some individuals occasionally enter Portuguese territory during the breeding season. These findings provide crucial insights for the conservation management of this species in Europe, where the vultures’ expanding presence requires coordinated efforts to address threats such as energy infrastructures. Ongoing monitoring is necessary to assess whether these individuals represent a temporary presence or a long-term colonization process.

Abstract Knowledge of the range of bird vocalisations is crucial not only for estimating the range of species acoustic communication but also for the detection radius of an observer in monitoring projects and expert assessments. Using calibrated sound recordings and parallel acoustic localisation, we assessed three methods of determining the sound pressure level for four species of rail [Corn Crake ( Crex crex ), Water Rail ( Rallus aquaticus ), Spotted Crake ( Porzana porzana ), Little Crake ( Zapornia parva )], whose calls differ significantly in temporal organisation and spectral composition. We calculated sound propagation over long distances, taking into account spherical propagation losses and atmospheric absorption. Atmospheric absorption was calculated including all frequencies contained in the signal. In the case of the Corn Crake in particular, we demonstrated that all spectral components of the signal must be considered when estimating its range. To ensure comparability between studies, we recommend establishing a reference library containing calibrated sound recordings . The results were discussed in the context of their significance for the acoustic communication of the species.

Abstract The ongoing global biodiversity loss is a major challenge of our time. It affects all groups of organisms, but is particularly well documented in birds. The Citril Finch Carduelis citrinella , one of the few bird species endemic to Europe, is one example currently suffering from substantial population declines. We here set out to document its population development over the past 14 years (records in 2011 and 2025) in a part of the Bavarian Alps and to identify the environmental factors being crucial for the occurrence of the species. In our study area around Garmisch-Partenkirchen, the Citril Finch has declined by about 48% between 2011 and 2025. Currently occupied territories, as compared to former territories or control sites, were characterised by a richer supply of flowers, particularly of the Asteraceae family, higher numbers of solitary trees, and a concentration on south-facing slopes. Moreover, areas with stable rather than declining populations showed a shorter distance to the nearest water source, a higher proportion of Mountain Pine, and a longer distance to forest edges. These findings indicate negative impacts of reduced grazing intensity and climate change (drought periods). Our results highlight that preserving the Citril Finch’s alpine habitats depends strongly on traditional, low-intensity farming and appropriate pasture care to maintain the necessary flower-rich, open to semi-open habitats with solitary trees. Providing supplementary water sources would help to counteract the increasing water shortage caused by climate change. Given the documented population decline, targeted conservation measures in the Bavarian Alps, the species’ stronghold in Germany, are urgently needed.

Abstract Host relatedness has been hypothesized to cause similarities in parasite assemblages and prevalence; we investigate this hypothesis in the ecologically diverse Caucasus Mountain region. Three Phylloscopus species sampled between 1998 and 2014 were analyzed to determine infection rates and to investigate whether P. collybita had low infection rates when compared to two congeners ( P. nitidus and P. sindianus ), as has been suggested. Generalized linear models were utilized to determine whether any differences in infection rates were related to environmental differences among sampling locations. Phylloscopus collybita and P. nitidus had comparable infection rates across and within haemosporidian genera; however, P. sindianus had distinctly lower infection rates. Models indicated that these infection differences were the result of differences between avian host species, rather than being influenced by other factors (e.g., host characteristics or environment). Results suggest that the host-relatedness hypothesis does not apply to here. Low haemosporidian infections rates of P. sindianus could be attributed to a higher elevational distribution, which may reduce contact with vector populations. One novel lineage was recovered from a P. nitidus individual in Armenia. This novel Haemoproteus lineage is similar in haplotype to another previously identified lineage found infecting P. trochiloides in India.

Abstract Species identification and recording in breeding bird surveys vastly rely on the registration of avian calls and songs. Despite comprehensive expert knowledge on species-specific activity patterns, data-based analyses of vocal activity patterns are lacking. Recent advances in passive acoustic monitoring allow the direct measurement of bird vocal activity at very high temporal resolution. We conducted a comprehensive survey, recording 25,000 h of audio data at 256 forest sites in Lower Saxony, Germany, to investigate vocal activity patterns of the European forest bird community. Our results reveal a high degree of inter-specific variability in seasonal and diel vocal activity patterns, including strong circular patterns along the day–night cycle and a significant seasonal component. Comparing acoustic detectability to species-specific survey recommendations revealed critical temporal discrepancies for 64.2% of species, and standard protocols (sunrise to 4 h after sunrise) showed discrepancies for 41.5% of species. This highlights the potential for temporal survey optimization to reduce imperfect detection and increase accuracy and precision. Emphasis should be given to the hours before and after sunrise and also sunset for sampling less detectable species. Combining observer-based surveys with passive acoustic monitoring might leverage the strengths of both methods. Our results also emphasize the potential of continuous recording schedules in passive acoustic monitoring to capture diverse temporal patterns. This study provides a baseline for future research on vocal activity patterns across habitats, throughout the year, and regarding anthropogenic impacts. Our findings may raise awareness among ornithologists about the sources of variation in acoustic detectability and its implications for breeding bird surveys, highlighting potential for methodological adjustments in survey timing and consequences for carful interpretation of bird surveys.