Investigating mirror responses in adult male zebra finches and house crows

Earlier evidence suggests that besides humans, some species of mammals and birds demonstrate visual self-recognition, assessed by the controversial 'mark' test.  Whereas there are high levels of inter-individual differences amongst a single species, some species such as macaques and pigeons which do not spontaneously demonstrate mirror self-recognition (MSR) can be trained to do so.  We were surprised to discover that despite being widely used as a model system for avian research, the performance of zebra finches (Taenopygia guttata) on the mark test had not been studied earlier. Additionally, we studied the behavior of another species of passerine songbirds (Indian house crows; Corvus splendens) on the mark test and other self-exploratory behaviors.  Although, a small number of adult male zebra finches appeared to display heightened responses towards the mark while observing their reflections, we could not rule out the possibility that these were specific to the mirror and not a part of general grooming.  In contrast, none of the house crows demonstrated mark-directed behavior or increased self-exploratory behaviors when facing mirrors.  Our study suggests that self-directed behaviors need to be tested more rigorously in adult male zebra finches while facing their reflections and these findings need to be replicated in a larger population, given the high degree of variability in mirror-directed behaviors.  We have also shown that house crows demonstrate early stages of self-awareness but do not pass the mark test.