To determine whether grackles innovate stick tool use, three experiments were conducted. In Experiment 1.1, the stick was placed on the table in all three 5 min trials (a(i–iii)). In Experiments 1.2 (b(i–iii)) and 1.3 (c(i–iii)), the stick was inserted into the apparatus for three consecutive trials, each with a different position: position 1 (left; trials 1, 4, 7, 10, 13), 2 (middle; trials 2, 5, 8, 11, 14) and 3 (right; trials 3, 6, 9, 12, 15). Experiment 1.2 had three 5 min trials and Experiment 1.3 had three 5 min trials per day for 5 days totalling 15 trials where each trial began with a demonstration from the experimenter.
To determine whether grackles innovate string pulling behaviour, two string pulling experiments were conducted: horizontal (a–c) and vertical (d). A habituation trial with a string inserted into the aviary next to a peanut (a), the observation period of the horizontal string pulling experiment with a choice between a broken string and a string that is connected to a cup of peanuts (b), the interaction period of the horizontal string pulling experiment where the bird had the opportunity to choose and pull a string (c) and the vertical string pulling experiment where they had the choice between pulling up a string with a block of wood or a piece of bread hanging at the end (d).
Results for each bird in each experiment: all individuals failed to innovate tool use (did not use the stick on the bread) and string pulling and their level of interaction with the stick or string was noted (X, did not pass habituation). Y, yellow; P, purple; B, blue; O, orange; R, red; G, green.