Living birds (n = 1776) were trapped and their ticks removed in Ebro Middle Basin (N.E. Spain) between January 1990 and July 1991. Positive hosts were T. troglodytes, Prunella modularis, Erithacus rubecula, Phoenicurus ochruros, Turdus merula, T. philomelos, Sylvia atricapilla, Phylloscopus collybita, Parus major, Certhia brachydactyla, P. pyrrhocorax, Fringilla coelebs, Emberiza citrinella, E. cirlus, E. cia and E. schoeniclus. Ticks collected (N = 255) for this study belong to the species Ixodes ricinus and Haemaphysalis punctata (immatures only), Ixodes frontalis (all stages) and Hyalomma marginatum (nymphs). The estimated prevalence for some bird species (Sylvia atricapilla, Phylloscopus collybita, Parus major and Pyrrhocorax pyrrhocorax) is very low, but others like Erithacus rubecula, Turdus merula and Turdus philomelos it reaches values of about 20 % or even higher. Most of the cases of parasitism by ticks are due to Ixodes frontalis. This tick can attach a wide range of hosts, although Erithacus rubecula and Turdus philomelos are the commonest. With regard to Ixodes ricinus, Turdus merula seems to be the most important carrier, whereas Emberiza cirlus may be the main host for Haemaphysalis punctata.