It is widely accepted that birds are able to taste toxic chemical substances in the wings of a butterfly by grabbing or pecking a small piece of the wing without disrupting the integrity of the integument ('beak mark tasting'). If found toxic, the bird will release the insect unharmed. This supposition has been used to explain some aspects of the interrelationship between birds as predators and butterflies as prey, especially the role of birds in the evolution of butterfly color patterns. It also is used to support the theory of aposematisc coloration, especially in butterflies. On the basis of the anatomy of the avian gustatory apparatus, the distribution of the taste buds in the beak cavity, and the physiology of taste, this author considers this supposition a misconception. The frequent beak marks seen on the wings of aposematic butterflies are not considered to be a proof of taste rejection by birds after contact with the chemical compound(s) supposed to provide the insect with a chemical defense, but a sign of active escape of the butterfly from its captor. Some aspects of the interrelationship between birds and butterflies, considered to be well explained on the basis of taste rejection of butterflies via 'beak mark tasting' by the birds, are critically discussed in this paper.