We review the literature on warning coloration in birds starting from Alfred Russel Wallace's premise that aposematism may advertise difficulty in subduing prey rather than simply unpalatability. Across diverse taxa, there is a good deal of anecdotal information to suggest that signals, usually involving conspicuous coloration, are associated not only with distastefulness but with informing predators that prey will be difficult to catch. There are also examples of aposematism being associated with both Müllerian and Batesian mimicry. In Aves there are now several examples of competitive mimicry which involves resembling larger non‐predator species. We stress that broad‐sense aposematism dissuading predators from attack can operate throughout the predatory sequence in birds. Throughout, we suggest new avenues of research that are likely to be promising and which will reinvigorate rigorous research on warning coloration in birds.