Oriental Hornbills Show Off Cognitive Skills That Rival Those Of Apes

Forget the term bird brain, many bird species are actually famous for their intelligence. And while parrots and corvids get all the credit, another group of birds is joining the ranks. The Oriental pied hornbill (Anthracoceros albirostris) is fascinating not just for its extraordinary mating and reproductive behaviors, but it’s also impressed scientists with its ability to understand object permanence.

Object permanence is the idea that an object still exists even when you can’t see it. In human children, there are six developmental stages that can test their understanding. Previously, other non parrot or corvid bird species have made it to stage four, but hornbills are the only other birds that have made it to stage six.

The idea that the birds would have a good understanding of object permanence occurs because, during the hornbills’ breeding stage, the female will seal herself inside the hollow cavity of a tree to lay her eggs. The male will bring food to her and their chicks even though he has never seen them as they remain sealed inside the tree with the female.


To test this, six oriental pied hornbills underwent a series of seven standard Piagetian tasks involving visible and invisible displacements. Jean Piaget was a Swiss psychologist who developed this scale and worked extensively on cognitive development in children. Stages one and two are about recognizing objects, so the tests with the hornbills began at stage three. 

The birds were trained to use a plastic bar with three prongs facing them, which they could use to indicate where they thought a food reward was out of three possible options hidden under red cups. The birds had never before been in a situation where the food reward was either partially or fully hidden from their view.

In the later stages of the experiment, a red box was introduced and the food was manipulated under the cups within the box before the box was shown to be empty,  adding greater complexity, as can be seen in this video of the experiments. 


Of the six hornbills tested, three achieved full stage six, or double invisible displacement. The other three achieved stage five, double visible displacement. 

These findings represent the first time a bird not in either the parrot or corvid families has displayed object permanence levels that are comparable to apes. 

The paper is published in Biology Letters

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