Handling techniques of an unbalanced stick tool in Goffin’s cockatoos (Cacatua goffiniana)

Abstract Parrots (Psittaciformes) exhibit unique morphological and behavioral traits that enable flexible, dexterous tool use, often comparable to that of apes. In tool-using species, attending to weight-related cues can enhance foraging efficiency by minimizing the energetic costs of tool manipulation. Previous research has shown that Goffin's cockatoos ( Cacatua goffiniana ) can detect and utilize weight cues, but their sensitivity to unbalanced objects remains unexplored. This study examined how Goffin’s cockatoos managed an unbalanced stick tool and the individual strategies they used to complete a stick-tool box task. We carried out a series of experiments using a setup with different levels of freedom, focusing on variations in insertion techniques and the birds’ ability to distinguish unequal weight distributions. At the group level, the cockatoos tended to handle the stick with the center of mass positioned closer to their grip. The birds also demonstrated highly individualized adaptations in their techniques when solving unfamiliar problems. We suggest that individuals that did not modify their techniques in this setup may still be capable of doing so under greater task constraints. Overall, these findings provide the first evidence that Goffin’s cockatoos can detect and adjust to uneven weight distribution in tools, underscoring their behavioral flexibility and sensitivity to physical tool properties.