Summary The principal European vector for Borrelia burgdorferi s.l., the causative agents of Lyme disease, is the host‐generalist tick Ixodes ricinus . Almost all terrestrial host‐specialist ticks have been supposed not to contribute to the terrestrial Borrelia transmission cycles. Through an experiment with blackbirds, we show successful transmission by the widespread I. frontalis , an abundant bird‐specialized tick that infe...