1. When searching for food, great tits (Parus major) can use herbivore-induced plant volatiles (HIPVs) as an indicator of arthropod presence. Their ability to detect HIPVs was shown to be learned, and not innate, yet the flexibility and generalization of learning remains unclear. 2. We studied if, and if so how, naïve and trained great tits (Parus major) discriminate between herbivore-induced and non-induced saplings of Scotch elm (Ulmus glabra) and cattley guava (Psidium cattleyanum). We chemically analysed the used plants and showed that their HIPVs differed significantly and overlapped only in a few compounds. 3. Birds trained to discriminate between herbivore-induced and non-induced saplings preferred the herbivore-induced saplings of the plant species they were trained to. Naïve birds did not show any preferences. Our results indicate that the attraction of great tits to herbivore-induced plants is not innate, rather it is a skill that can be acquired through learning, one tree species at a time. 4. We demonstrate that the ability to learn to associate HIPVs with food reward is flexible, expressed to both tested plant species, even if the plant species has not coevolved with the bird species (i.e. guava). Our results imply that the birds are not capable of generalising HIPVs among tree species but suggest that they either learn to detect individual compounds or associate whole bouquets with food rewards.

Birds were split into three groups. Two groups were trained to respective smells  or kept naive (Trained to: Psidium, Ulmus, Control).

Bird = ID of the bird and each bird entered severa pair-wise tests in which it was suppose to search on trees familiar/unfamiliar to it and trees either chemicall induced or non-induced. The "induced psidium or induced ulmus " were considered as a focal tree, to which the data were related. The type of the tree on the other side of the cage was used as an explanatory factor and is noted in column "Other side".

Measured variable were TimeClose = number of seconds spent in the proximity of the tree, TimeOn - time spent onthe tree by real searching for prey, these two variables were then related to the total length of the time spent  (TotalTimeCloseTree, TotalTimeOnTree) at any of the offered tree. THe values were expressed as bonamial (Binom) or in percentages (perc).

Experiments were run at two cages, their nick-names are "wooden" and "metal".