True bugs are generally considered to be well protected against bird predation. Sympatric species that have similar warning coloration are supposed to form a functional Müllerian mimetic complex avoided by visually oriented avian predators. We have tested whether these assumptions hold true for four species of European red-and-black heteropterans, viz. Pyrrhocoris apterus, Lygaeus equestris, Spilostethus saxatilis, and Graphosoma lineatum. We found that individual species of passerine birds differ in their responses towards particular bug species. Great tits (Parus major) avoided all of them on sight, robins (Erithacus rubecula) and yellowhammers (Emberiza citrinella) discriminated among them and attacked bugs of some species with higher probability than others, and blackbirds (Turdus merula) frequently attacked bugs of all the tested species. Different predators thus perceive aposematic prey differently, and the extent of Batesian-Müllerian mimetic complexes and relations among the species involved is predator dependent.