Jackdaws' frequencies of self-directed behaviours in experimental stage 4 (mark test).

Birds were given a total of eight sessions each, two sessions per experimental condition (in columns). Numbers show the total number of self-directed behaviours in both sessions. In each case, the first value shows the number of mark-directed actions, and the second refers to self-directed actions towards other parts of the body. A plus sign (+) indicates that the bird was successful removing the sticker in any of the sessions. None of the individuals removed the sticker more than once.