Photographs of Bruce handling objects larger than his preening pebbles, namely: (a) a slice of carrot, (b) a stone, (c) a piece of bark, (d) a black token used in previous cognitive experiments he was a part of; a close-up image (e) demonstrates how he uses his tongue and lower mandible to hold these objects. Image credit: Bastos et al., doi: 10.1038/s41598-021-97086-w.
“Most reports of tooling in birds revolve around foraging,” said study lead author Amalia Bastos, a Ph.D. candidate in the School of Psychology at the University of Auckland, and colleagues from the University of Auckland and the ELTE Eötvös Loránd University.
“Among parrots this is more common in captive settings, for example, greater vasa parrots use small stones to scrape or break up shells, which they then ingest, hyacinth macaws use wedges to manipulate nuts, and Goffin’s cockatoos innovate and manufacture stick tools to retrieve out-of-reach food.”
“Despite not habitually using tools in the wild, kea parrots (Nestor notabilis) learn to insert sticks and other objects into traps designed for pest species such as stoats, which allows them to safely access egg bait placed inside.”
“Kea also probe at and set off unbaited traps, an apparently non-functional behavior which may be playful or exploratory in nature.”
“In captivity, kea also readily learn to use stick tools for extractive foraging in experimental settings.”
In the study, the researchers observed a disabled kea named Bruce at Willowbank Wildlife Reserve in Christchurch, New Zealand, who has overcome his disability by using pebbles to preen himself.
“Bruce was found as a juvenile by a researcher at Arthur’s Pass in 2013 with the upper half of his beak missing,” they explained.
“It’s not known exactly how the injury occurred, but it is thought to be the result of an accident with a pest trap.”
“He was brought to the South Island Wildlife Hospital, where he was nursed back to health and now lives in a large aviary at Willowbank Wildlife Reserve.”
“Although keepers ensure that Bruce has access to soft foods which can be eaten without an upper bill, he has also learned to eat harder foods by pressing them up against hard objects.”
“Bruce has adapted well to his injury and can manipulate various objects by holding them between his tongue and lower mandible.”
To establish his behavior was, in fact, intentional tool use, the scientists observed Bruce across nine days.
They recorded instances of him manipulating objects or preening himself and were able to establish five lines of evidence to show that his tool use is intentional.