A disabled kea parrot fights smarter to rule his roost

Kea parrots are famed for their intelligence, complex behaviour and cheeky personalities. Bruce is a disabled kea – missing his upper beak – who first made international headlines in 2021 due to his innovative use of stone tools to preen himself. 

A new study from Te Whare Wānanga o Waitaha | University of Canterbury (UC) with the collaboration of the Institut de Neurociències of the Universitat Autònoma de Barcelona (INc-UAB) now shows how Bruce has used innovation to thrive in his social group, despite his disability.

Published in Current Biology, the research led by postdoctoral researcher Dr Alex Grabham and Professor Ximena Nelson from UC’s School of Biological Sciences and Professor Alex Taylor, from INc-UAB, carried out a deep dive into Bruce’s social life to find out how he interacts with other kea in his circus (the collective noun for a group of kea) at Willowbank Wildlife Reserve near Christchurch. 

The team recorded fights, feeding station interactions, and preening bouts, while also collecting droppings to measure corticosterone hormone levels. From this, they were able to map the dominance hierarchy of the group and how it relates to stress. 

The results were not what they expected.

“Everything we know about animal contests predicts that the bigger, better-armed competitor should prevail. Missing his entire upper beak should have put Bruce at a serious disadvantage. Yet Bruce, the only disabled bird in the group, was undefeated in his dominance interactions with other males. Bruce was the alpha male,” Dr Grabham says. 

The researchers found that Bruce has innovated a fighting technique never seen in other kea: jousting. Other birds in his circus typically bite downward onto their opponents’ necks. Bruce jousted with his exposed lower beak by jutting his head forward at close range with an extension of his neck, or charging from a distance with a run or jump that left him overbalanced with the force of motion. He attacked with his beak more than five times as often as his intact peers, striking from different angles, and distributing strikes across the head, back, wings, and legs. The result: his jousting displaced opponents 73% of the time, compared to 48% when he kicked.

Bruce’s achievement is the first known case of a disabled animal of any species individually reaching and maintaining alpha-male status on its own, without allies, through behavioural innovation. “Bruce has not just found a way to compensate for his missing beak; he innovated a completely novel fighting style and turned it to his advantage,” Dr Grabham says.

The deep dive into Bruce’s social life revealed the benefits of alpha-male status. Bruce’s stress-related hormone levels were lower than those of any of his peers, he had priority access to most of the feeder stations in the aviary, and he received social grooming from the subordinate males. Lower-ranked males carefully preened the inside of his lower beak to remove debris he struggles to remove himself.

“Subordinate birds groomed him and never challenged him while he ate, likely contributing to his low corticosterone levels. Bruce is a profound example of a disabled animal not just surviving, but thriving,” Dr Grabham says.

The findings raise questions about care for disabled animals. Professor Taylor says Bruce demonstrates that well-intentioned interventions, such as prosthetics, may not always improve a disabled animal’s quality of life. “Bruce is a great example of how behavioural innovation can improve animal wellbeing and welfare,” Professor Taylor says. “Bruce´s disability seems to be the driving force in him achieving the top rung of kea society.”

Professor Nelson agrees. “The flexibility of what animals can achieve is only truly understood when you look at behaviour and its underlying physiology in combination.

“Bruce’s success forces us to rethink what disability means for behaviourally complex species.”