Scientists puzzled by these birds scoring as high as primates in cognitive tests

Level of skill displayed by breeding hornbills is intricate, involving integration of memory, reasoning, and inference

Scientists have found that some species of birds are capable of passing advanced cognitive tests on a level previously only associated with primates.

Tests conducted with oriental pied hornbills, a tropical bird distributed across southeast Asia, showed they were capable of understanding object permanence – the idea that things continue to exist even when they are out of sight.

Object permanence has played an important role in the survival and evolution of both humans and primates, with the higher cognitive ability to mentally picture objects even when they are not directly accessible providing a number of benefits to the species.

While previous studies have shown that the oriental pied hornbill has remarkable adaptability in various environments, this cognitive feature has never before been documented in the species.

These hornbills have a unique breeding behaviour that has intrigued scientists, and singled them out as candidates who may pass object permanence tests.

When the female hornbill is about to lay eggs, she seals herself inside a cavity made of mud, saliva, bark, and fruit, and the male feeds her and their offspring without any visual contact.

For any of their offspring to ever survive, male hornbills must understand that the female still exists even when out of sight.

“From an evolutionary perspective, the ability to represent other animals and objects when they are out of sight provides great adaptive advantages in activities such as foraging and avoiding predation,” researchers explained.

Scientists have suspected this trait strongly suggested the presence of object permanence to some degree in the bird.

Previous studies have shown some species of crows and parrots are also capable of this trait.

In the new study, published in the journal Biology Letters, researchers subjected six hornbills to standard object permanence tests in a lab environment involving the visible and invisible displacements of things kept in front of the birds.

The hornbills were trained to indicate where a visible treat is with a peck.

A series of tests then subjected the birds to increasingly difficult levels of object permanence.

In one of the highest levels of the test, the hornbills saw a reward get placed under one cup, which was then moved to another cup.

By pecking and showing which cup the treat ended up in, the test birds demonstrated an understanding of the object’s displacement.

All the birds displayed consistent behaviour demonstrating the presence of this cognitive feature.

In the final stage of the test, the birds did not get to see the treat move from one cup to another. Insead the treat was hidden under a box and then moved under a larger cup unseen.

Three of the birds could figure out that when the red box was taken out and shown to be empty, the treat must have been left behind under the cup, despite not actually seeing this happening.

The three birds that completed this final stage all had experience breeding, while the three who failed it did not.

“The subjects consistently demonstrated spontaneous object permanence in all stages leading up to the invisible displacement stage,” researchers wrote.

This understanding of invisible displacement, scientists say, is intricate and involves an integration of various cognitive skills, such as memory, spatial reasoning, and logical inference.

“To the best of our knowledge, oriental pied hornbills are the first bird species outside of the corvid and parrot families to display object permanence levels comparable to apes,” researchers wrote.