Background: Previous studies on the tick infestation of birds in the Carpathian Basin focused on songbirds (Passeriformes). Thus, the primary aim of the present work was to extend the scope of previous studies, i.e. to include aquatic (water-associated) bird species in a similar context, especially considering that these birds are usually long-distance migrants. Methods: Between March 2021 and August 2023, 11,919 birds representing 126 species were checked for the presence of ticks. From 352 birds belonging to 40 species, 905 ixodid ticks were collected. Tick species were identified morphologically and/or molecularly. Results: Ticks from avian hosts belonged to seven species: Ixodes ricinus (n = 448), I. frontalis (n = 31), I. festai (n = 2), I. arboricola (n = 36), I. lividus (n = 4), Haemaphysalis concinna (n = 382) and Dermacentor reticulatus (n = 2). Nymphs of I. ricinus occurred with a single activity peak around March–May, whereas its larvae typically infested birds in May, June or July. By contrast, H. concinna usually had its activity maximum during the summer (nymphs in June–July, larvae later in July–August). Interestingly, two ornithophilic species, I. frontalis and I. arboricola, were most active around winter months (between October and April). A significantly lower ratio of aquatic birds was found tick-infested than songbirds. Several new tick–host associations were revealed, including I. ricinus from Greylag Goose (Anser anser) and D. reticulatus from Great Egret (Ardea alba) and Sedge Warbler (Acrocephalus schoenobaenus). Ticks were collected for the first time in Europe from two species of predatory birds as well as from Little Bittern (Ixobrychus minutus). Bird species typically inhabiting reedbeds were most frequently infested with H. concinna, and most ticks localized at their throat, as opposed to forest-dwelling avian hosts, on which I. ricinus predominated and ticks were more evenly distributed. Conclusions: In the evaluated region, aquatic birds appear to be less important in tick dispersal than songbirds. However, newly revealed tick-host associations in this category attest to their hitherto neglected contribution. The results suggest that the habitat type will have significant impact not only on the species composition but also on the feeding location of ticks on birds. Graphical Abstract: (Figure presented.)

Birds are long-known as important disseminators of ixodid ticks, in which context mostly their latitudinal, south-to-north migration is considered. However, several bird species that occur in the eastern part of the northern Palaearctic are known to migrate westward. In this study, a female tick collected from the sedge warbler, Acrocephalus schoenobaenus, in Lithuania was identified morphologically and analyzed with molecular-phylogenetic methods. In addition, literature data were reviewed on ixodid tick species known to be associated with birds that have recorded east-to-west migratory route in the Palaearctic. The tick collected from A. schoenobaenus was morphologically identified as Ixodes apronophorus. Two mitochondrial genetic markers for this specimen showed 100% identity with a conspecific tick reported previously in Western Siberia, Russia. Based on literature data, as many as 82 bird species from 11 orders were found to have records of ringing in the easternmost part of the northern Palaearctic and recaptures in Europe. Of these bird species, 31 ixodid tick species were reported in the Euro-Siberian region. Nearly all passeriform bird species with east-to-west migration were reported to carry ticks, whereas no reports of tick infestation were documented from the majority of wetland-associated bird species, mostly from the orders Anseriformes and Charadriiformes. The first European sequences of bona fide I. apronophorus revealed genetic connectedness with conspecific ticks reported from Siberia. Since the principal hosts of this tick species are rodents which do not migrate large distances, the most likely explanation for genetic similarity in this direction is dispersal of this tick species via migratory birds. Given the high number of tick species that are known to associate with bird species migrating in westward direction, this appears to be an important means of the gene flow between geographically distant tick populations in the northern Palaearctic.

The southern part of Europe is one of the most species-rich regions from the point of view of the genus and subgenus Ixodes . However, numerous unresolved or questionably interpreted issues exist in the context of tick species indigenous to Mediterranean countries, such as the validity of Ixodes festai , synonymy of Ixodes tatei with Ixodes eldaricus (never tested molecularly) or the haplotype heterogeneity of Ixodes gibbosus . In this study, 21 specimens of six tick species from the subgenus Ixodes were compared morphologically with high resolution digital microscopy and also analyzed with molecular-phylogenetic methods based on two mitochondrial genetic markers. The nymphs of I. eldaricus and I. tatei showed differences in the morphology of the scutum and basis capituli. Both the nymph and the females of I. festai could be distinguished from those of I. eldaricus , I. ventalloi and I. acuminatus . A female tick resembled I. gibbosus but was also different from this species, based on its descriptions. Analysis of phylogenetic relationships confirmed with moderate to strong support that all six species examined in this study represent different taxa of the subgenus Ixodes , including a previously unknown sister species to I. gibbosus . The latter is recognized and described here as a new species, Ixodes paragibbosus Hornok and Kontschán, sp. nov. Based on findings of this study, the tick species I. tatei Arthur, 1959 should be resurrected and reestablished. Morphological and phylogenetic comparisons performed here (including the first barcoding sequences of I. eldaricus and I. festai) confirm that the latter is a valid species, distinct from both I. eldaricus and I. ventalloi . For the differential diagnosis of the above species, the results highlight the importance of observing (among other structures) the auriculae, the internal spur of coxa I and the hypostome.

Ixodes arboricola and Ixodes lividus are ornithophilic tick species. The former is typically associated with tree-hole dwelling birds, while the latter is a host-specific parasite of sand martins (Riparia riparia). These two tick species share important morphological characters that make them difficult to identify when they are collected from atypical hosts, such as birds of prey. Despite this, high resolution digital pictures have not been reported to compare I. arboricola and I. lividus, nor was their complete mitogenome reported. The aim of this study was to compensate for this lack of illustrations and sequence data. Nymphs and females of I. arboricola and I. lividus were used for morphological comparison, and one specimen of each species to generate mitogenome sequences. The results showed that females of these two species are different in the shape of their scutum, porose areas, the length of basis capituli, palps, coxae, genital pore, anal groove and tarsus I. On the other hand, nymphs of I. arboricola and I. lividus can be distinguished according to their cervical grooves, cornuae, auricular ridges and spiracular plates. The mitochondrial genome size was 14,539 and 14,536 bp, for I. arboricola and I. lividus, respectively. The mitogenome sequences of I. arboricola and I. lividus were 91.1% identical to each other. Phylogenetic analysis of Ixodes species showed that I. arboricola and I. lividus are sister species, and cluster together with Ixodes crenulatus/canisuga under strong support. In conclusion, results of this study confirmed that the front of the basis capituli is crucial in distinguishing Ixodes species, especially in the subgenus Pholeoixodes where these two species are phylogenetically closest related to I. canisuga. Another phylogenetically relevant morphological character is the scutal surface which is wrinkled (rugose) as a common feature of Pholeoixodes species in the clade of I. arboricola and I. lividus (including I. canisuga, I. rugicollis and I. ariadnae). Although the host ranges of I. arboricola and I. lividus do not substantially overlap, they may transmit some of the shared pathogens. Relevant data indicate that the eco-epidemiological significance of the two ornithophilic tick species studied here may in part be similar and they may play a role in the transmission of rickettsiae, borreliae and viruses of which birds act as reservoirs.

Tick infestation of songbirds has been extensively studied at global and regional scales but relevant data on birds of prey remain scarce and fragmentary. Raptors are of particular epidemiological relevance because their large size, wide-ranging movements and nesting habits may facilitate long-distance dispersal of ticks, and endophilic tick species (e.g. from prey animals) may even persist in their re-used nests. In this study, we aimed to compensate for the lack of comprehensive data in this context. First, more than 1800 birds of prey were examined at 61 sites in Central and South-Eastern Europe, encompassing both continental and Mediterranean climatic regions. Ticks (n = 839) were obtained from 98 birds representing 13 raptor species from three avian orders. Twelve tick species were identified, the most abundant being Rhipicephalus turanicus, Haemaphysalis concinna and Ixodes ricinus. Several previously unknown tick–host associations were revealed. Molecular-phylogenetic analysis showed that sequences of Ixodes arboricola from Tawny Owls (Strix aluco) clustered separately from other conspecific sequences, raising the possibility that Ixodes strigicola Schulze and Schlottke, 1929 is a valid species. Owls proved to be the most heavily tick-infested, particularly Eurasian Eagle-Owl (Bubo bubo) nestlings. Endophilic and rodent-associated tick species were significantly more common on owls and on bird species nesting in cavities or buildings, whereas diurnal raptors were predominantly infested by generalist and exophilic ticks. These patterns highlight the importance of nesting ecology and prey composition in shaping tick assemblages on raptors. The results provide novel insights into tick–raptor associations, contribute new records of tick species from birds of prey, and improve our understanding of the role of raptors in tick maintenance and dispersal which appears to be particularly important in the case of cavity-nesting species. In addition to field sampling, a comprehensive database from nearly 150 published sources revealed that 32 tick species have been reported from birds of prey in the Western Palearctic to date.