The first step towards the acquisition of the proper instinct might have been mere unintentional restlessness on the part of the young bird, when somewhat advanced in age and strength; the habit having been afterwards improved, and transmitted to an earlier age.
Instintu hau erdiesteko lehen urratsa kukukumearen asmogabeko gerakatasun hutsa izan zitekeen, adin eta indar handixeagoa zuenean, aztura hau gero hobetu eta gazteagotan transmitituko zelarik.