The development of object permanence was investigated in black-billed magpi
es (Pica pica), a food-storing passerine bird The authors tested the hypoth
esis that food-storing development should be correlated with object-permane
nce development and that specific stages of object permanence should be ach
ieved before magpies become independent As predicted, Piagetian Stages 4 an
d 5 were reached before independence was achieved, and the ability to repre
sent a fully hidden object (Piagetian Stage 4) emerged by the age when magp
ies begin to retrieve food. Contrary to psittacine birds and humans, but as
in dogs and cats, no "A-not-B error" occurred. Although magpies also maste
red 5 of 6 invisible displacement tasks, evidence of Piagetian Stage 6 comp
etence was ambiguous.