Avoidance of aposematic prey in European tits (Paridae):: learned or innate?

Predators may either learn to avoid aposematic prey or may avoid it because of an innate bias. Learned as well as innate avoidance has been observed in birds, but the existing evidence is based on experiments with rather few unrelated model species. We compared the origin of avoidance in European species of tits (Paridae). First, we tested whether wild-caught birds (blue tits, great tits, crested tits, coal tits, willow tits, and marsh tits) avoid aposematic (red and black) adult firebugs Pyrrhocoris apterus (Heteroptera) more than nonaposematic (brown painted) ones. Larger proportion of birds avoided aposematic than brown-painted firebugs in majority of species (except coal tits). Second, we tested whether naive hand-reared birds of 4 species (blue tits, great tits, crested tits, and coal tits) attack or avoid aposematic and nonaposematic firebugs, both novel for them. Behavior of the naive blue tits and coal tits was similar to that of the wild-caught birds; majority of them did not attack the firebugs. Contrastingly, the naive great tits and crested tits behaved differently than the wild-caught conspecific adults; majority of the wild-caught birds avoided the aposematic firebugs, whereas the naive birds usually did not show any initial avoidance and had to learn to avoid the aposematic prey. Our results show that the origin of avoidance may be different even in closely related species. Because blue tits and coal tits avoided not only aposematic firebugs but also their brown-painted form, we interpret their behavior as innate neophobia rather than innate bias against the warning coloration.