The “Cultural Transmission Hypothesis” and the “Alerting Others Hypothesis” of enemy recognition in birds was examined in mobbing experiments with captive blackbirds. Observer birds learned to mob a novel non-raptorial bird more strongly as a consequence of witnessing another bird mob strongly at the site of presentation. Strength of the observer's enhanced response was comparable to that elicited by a genuine predator. Under identical conditions, observers were also tutored to mob an unnatural, similar-sized object more strongly than initially but less intensely than to the novel bird after conditioning. Habituation to the novel bird did not impair subsequent conditioning. Cultural Transmission was effective along a “chain” of at least six birds. The phenomenon is discussed in terms of selfish benefits, kin selection and blackbird dispersal.