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.

既往研究证据表明，除人类外，部分哺乳类与鸟类物种可展现视觉自我识别能力，该能力通过颇具争议的标记测试（mark test）进行评估。尽管同一物种内部个体间存在显著差异，但部分不会自发表现出镜像自我识别（mirror self-recognition，MSR）的物种，如猕猴与鸽子，可通过训练获得该能力。令我们意外的是，尽管斑胸草雀（Taenopygia guttata）被广泛用作鸟类研究的模式生物，但其在标记测试中的表现此前从未被探究过。此外，我们还针对另一种雀形目鸣禽——家鸦（Corvus splendens），探究了其在标记测试与其他自我探索行为中的表现。尽管少量成年雄性斑胸草雀在观察自身镜像时，似乎对标记区域表现出增强的响应，但我们无法排除这类响应仅针对镜像、而非常规理毛行为的可能性。与之相反，所有家鸦均未表现出指向标记的行为，或在面对镜像时出现自我探索行为增强的现象。本研究表明，针对成年雄性斑胸草雀的镜像自我导向行为，需采用更严谨的测试方案；鉴于镜像导向行为存在高度变异性，上述发现需在更大样本群体中重复验证。我们还证实，家鸦虽展现出自我意识的早期阶段，但未能通过标记测试。