Two Ehrlichia pathogens were found in immature Ixodes ricinus (L.) ticks collected from migratory passerine birds in the Curonian Spit area of the Baltic Region of Russia (Kaliningrad enclave). During the spring and fall of 2000, 1,606 passerine birds (eight species) were collected; 6.8% of them (110/1,606) were infested by ticks, and 51.8% (57/110) of tick clusters contained various human pathogenic microorganisms. Human monocytic ehrlichiosis (HME) and human granulocytic ehrlichiosis (HGE) agents were found in 14% (8/57) of cases. Borrelia afzelii, Borrelia garinii, and Borrelia burgdorferi sensu stricto were found in 92.9% (53/57) of the ticks. In five out of eight cases, infection of both Ehrlichia and Borrelia were obtained. In one case, a single nymph contained HME, B. afzelii, and B. garinii. Borrelia burgdorferi s.s. and B. afzelii were found together in one pool of four nymphs and one larva. All agents were identified using polymerase chain reaction and species-specific primers. In 8.8% of the ticks collected from birds in the fall and 22% in the spring, pathogens were isolated from attached co-feeding nymphs and larvae. These data demonstrate that Ehrlichia exchange could occur between co-feeding ticks on animals without systemic infection.