Pattern of visuospatial lateralization in two corvid species, black-billed magpies and Clark's nutcrackers.

Cerebral lateralization is widespread amongst vertebrate species suggesting advantages are gained by having one of the brain's hemispheres exert dominant control over certain cognitive functions. A recently devised task for assessing lateralization of visuospatial attention by birds (Diekamp et al., 2005) has allowed researchers to suggest the corpus callosum may not be necessary for the emergence of such asymmetries. More recently, this task has been adopted to examine the embryonic development of lateralization in birds, research which may provide important insights as to the underlying genetic mechanisms (Chiandetti, 2011; Chiandetti et al., 2013) of vertebrate cerebral lateralization. However, to date only chicks and pigeons have been used in this paradigm. Thus, it is unclear whether other avian species will also show lateralization of visuospatial attention during this task. Here, we examined the pattern of visuospatial lateralization in two corvid species: social black-billed magpies (Pica hudsonia) and non-social Clark's nutcrackers (Nucifraga columbiana). We find that neither the magpies nor the nutcrackers show evidence for population level lateralization or predictable individual level lateralization, as only a subset of individuals of each species showed a significant individual bias, which were rarely stable over repeated testing.