No evidence for side preference or handedness in a New Zealand rail species with habitual foot-usage, the pukeko.

Many animals show evidence of cerebral lateralisation, i.e. morphological differences and functional specialisation in two separate hemispheres of the brain. Laterality in behaviour is commonly used as an indicator of cerebral lateralisation, as asymmetry in actions often mirrors asymmetry in the brain. It has been predicted that species that habitually use limbs to manipulate food or resources will develop strong limb preferences, and data in a limited set of taxa support this prediction. However, relatively few species have been studied, limiting our understanding of how taxonomically widespread such behavioural asymmetries might be, and thus how such preferences evolve. Here, we test for limb preference within a new taxon, the rails, using the pukeko (Porphyrio p. melanotus), a species that frequently uses its feet while feeding. We quantified foot-use of 359 individual pukeko and found that though some individuals show preferences, there was no overall side preference at the population level - roughly equal numbers of individuals showed a left preference, a right preference, or no preference, though we detected a weak preference in adults during long-use behaviours. We also found that the strength of side preference weakened with increased observations of foot-usage. Finally, though patterns were similar when looking at brief and longer foot uses, the within-individual relationships between preference in those contexts was only significant in birds that used their feet at least five times. Together these findings question whether habitual foot use will lead to side preference and suggest that the apparent wide-spread and prevalent nature of this pattern in current literature may be due to a publication bias rather than the general presence of a relationship. Studies that cover a great taxonomic spread are needed.