Birds, particularly passerines, can be parasitized by Ixodid ticks, which may be 
infected with tick-borne pathogens, like Borrelia spp., Babesia spp., Anaplasma, 
Rickettsia/Coxiella, and tick-borne encephalitis virus. The prevalence of ticks 
on birds varies over years, season, locality and different bird species. The 
prevalence of ticks on different species depends mainly on the degree of feeding 
on the ground. In Europe, the Turdus spp., especially the blackbird, Turdus 
merula, appears to be most important for harboring ticks. Birds can easily cross 
barriers, like fences, mountains, glaciers, desserts and oceans, which would 
stop mammals, and they can move much faster than the wingless hosts. Birds can 
potentially transport tick-borne pathogens by transporting infected ticks, by 
being infected with tick-borne pathogens and transmit the pathogens to the 
ticks, and possibly act as hosts for transfer of pathogens between ticks through 
co-feeding. Knowledge of the bird migration routes and of the spatial 
distribution of tick species and tick-borne pathogens is crucial for 
understanding the possible impact of birds as spreaders of ticks and tick-borne 
pathogens. Successful colonization of new tick species or introduction of new 
tick-borne pathogens will depend on suitable climate, vegetation and hosts. 
Although it has never been demonstrated that a new tick species, or a new tick 
pathogen, actually has been established in a new locality after being seeded 
there by birds, evidence strongly suggests that this could occur.