We shaped two demonstrators to remove the stopper from an
inverted, opaque, test tube containing 0.5 g of mixed seeds.
The stopper was fitted with a wooden tab that the pigeons
could peck or grasp with the bill and twist in a downward motion
to release the seeds into their food dish (see Giraldeau
and Lefebvre 1987 for a description of the task). Demonstrators
were considered efficient when they could routinely
open the test tube in less than 5 s after presentation of the
apparatus. Before the social learning test, the subjects were
transferred to smaller 23 cm × 38 cm × 28 cm cages in
which all sides were opaque except the door in the front.
These cages had the advantage of offering very few distractions
and ensured that the birds were facing the door most
of the time. A 20 cm × 5 cm hole in the door allowed the
birds access to the apparatus. A control trial was performed
prior to the social learning test: the apparatus was placed in
front of each individual for 20 min to control for spontaneous
opening; no birds opened during this period.