This study provides the first comprehensive investigation of the relationships between mistletoes Viscum album L. (Santalaceae) and Loranthus europaeus Jacq. (Loranthaceae) and avian species in Europe. Its aims were to: (1) document the diversity and richness of European bird species that use mistletoe for nesting and shelter; (2) determine the factors influencing nest site location in mistletoe by different bird species; and (3) assess the impact of anthropogenic factors on the mistletoe nesting site location and possible selection of mistletoe as nesting sites. Mistletoe is highlighted as both a keystone resource and a critical arboreal microhabitat for nesting and roosting, shaping local patterns of bird diversity and abundance in European ecosystems. We recorded 41 species of European breeding birds from 18 families nesting in mistletoe, with V. album supporting 39 species and L. europaeus hosting 7. Species richness of mistletoe-associated birds was higher in natural landscapes than in urban ones. Nevertheless, in urban environments, mistletoe remains an important nesting site, particularly for the Woodpigeon Columba palumbus, Fieldfare Turdus pilaris, Eurasian Collared Dove Streptopelia decaocto, Hooded Crow Corvus cornix, and Eurasian Magpie Pica pica. The impact of tree structure, mistletoe morphology, and environmental factors on nest site location in mistletoe clumps varied among bird species, reflecting strong species-specific preferences consistent with their general nesting behavior.
Long-term analyses of autumn bird migration in Central Eastern Europe remain scarce, particularly those based on standardised visual observations. We analysed 11 years of systematic counts (2012-2022) conducted by an experienced citizen scientist at a single site in northern Austria near the Czech border. The dataset comprises 5,411 quarter hours of observation from 6 a.m. to 12 a.m. between September and October, yielding 479,307 migrating individuals of 100 species. Migration intensity, measured as mean traffic rate (MTR), increased overall by 2% per year. This trend was driven by short-distance migrants (+3% annually), while long-distance migrants declined (-5% annually), with the steepest decreases in farmland species. Urban breeders showed moderate declines independent of migration strategy. Raptors increased markedly (+8% per year), primarily due to Common Buzzard Buteo buteo and Common Kestrel Falco tinnunculus. Phenological analysis revealed decreasing trends in September but increasing trends in October, indicating delayed departures for short-distance migrants and, unexpectedly, also for long-distance migrants, albeit at low abundance levels. Raptors showed consistent increases in both months. These findings demonstrate contrasting trends between migration strategies and breeding habitats, highlighting the role of different ecological pressures.
Parasites may influence ecological and evolutionary processes of their host species. Several studies have consistently shown that traits signaling individual quality are typically condition-dependent and that the presence of parasites negatively affects both an individual's condition and ornamentation. Here, we screened for multiple macro and microparasites and investigated whether infestation by lice impacts the condition, immune status, and ornamentation in Silver-beaked Tanagers Ramphocelus carbo. We found that 62.5% of individuals were parasitized, with feather lice being the most prevalent parasite. Blood parasites were scarce, with Plasmodium found in only 6.25% of individuals. No case of concomitant infection was recorded. We observed a positive association between body condition and total white blood cell count, whereas a negative association was found with the heterophil-to-lymphocyte ratio. Testes size and beak ornament size were not associated with condition. We also found a marginally non-significant tendency for plumage hue in adult males to be negatively associated with the number of lice. The low prevalence of blood parasites may be due to diminished vector abundance or high resistance and tolerance in this host population. While some of the traits we investigated were condition-dependent (such as immune status), our study revealed that parasite abundance did not significantly influence them. Nevertheless, the association between the number of lice and coloration may indicate that circulating carotenoids may play a vital role in immune response in redder males. These findings underscore the intricate interplay between parasites and avian characteristics. Future research should investigate the relationship of how circulating carotenoids may be used in coloration and their effects on immunological responses, with or without parasite infection.
