HANDEDNESS IN THE BROWN‐THROATED PARAKEET ARATINGA PERTINAX EST RELATION WITH SKELETAL ASYMMETRY

Abstract

SUMMARYObservations on 56 specimens of Aratinga pertinax when bringing food to the beak prove that 28 birds were right‐handed while the other 28 were left‐handed. A biometric analysis reveals a slight departure from bilateral symmetry in hindlimb bones in close relationship with handedness. In the right‐handed birds, there is a significant predominance in the length of the right hindlimb as a whole and all right limb segments. The opposite holds true in left‐handed parrots (except for the femur). Right‐handed birds are in general more highly asymmetrical than left‐handed ones. There is a positive correlation between asymmetry of homologous segments of a pair of limbs and the asymmetry of the other segments of the same pair of limbs. The absence of significant negative correlations between bilateral differences of the different segments of a limb indicates that departures from bilateral symmetry tend to affect the limb as a whole, and thus is not in agreement with the rule of compensating variations.