A case of quick problem solving in birds: string pulling in keas, Nestor notabilis

摘要

Keas are extremely inquisitive birds that explore and manipulate objects with their beak and feet when foraging or at play. We investigated how captive keas face a problem that they have never encountered before: food objects suspended from a long string. Using this well-probed test for means-end comprehension, our aim was to see whether, and how, the keas solved the task. The seven subjects showed immediate interest in the string and, with the exception of a fledgling, reached the food by repeating combined actions of pulling up the string with the beak and holding loops of it against the perch with a foot. Four keas completed the first trial within a few seconds, by showing only goal-directed behaviour, thus executing the solution in a manner that could not be improved upon in nine further trials. The behaviour of the fledgling shows that the crucial element of the string-pulling competence is the beak-foot coordination. We then conducted four different two-string discrimination tests varying in the attachments and the spatial relationship of the strings to assess the keas' level of understanding of the functional properties of the task. The subjects' performance suggests that their attention is drawn very quickly to the relevant properties of the strings, that is, their connection between perch and food. These findings contribute to the ongoing debate on the distribution of higher cognitive skills in the animal kingdom by showing high levels of sensorimotor intelligence in animals that do not use tools.