Jackdaws' behavioural data for experimental stages 1 (30-min baseline session with cardboard) and 2 (150-min mirror exposure sessions).

F = Female, M = Male. Individuals marked with two rings of the same colour were captured in the wild; individuals marked with only one ring were hand reared in the laboratory. Behavioural data have been standardized to calculate each value per hour. Data corresponding to the mirror column has been calculated as the mean value of the three sessions performed with the mirror. Looks behind the mirror involves going behind the mirror and stopping to have direct visual inspection at close range.