Goffin cockatoos are extremely intelligent and in some ways surpass even primates. Now an experiment shows that when birds want to transport objects with their beaks, they first check their weight and then usually choose the lighter object. But occasionally they also resort to the heavier option. This behavior suggests that the cockatoos avoid unnecessary effort to conserve energy. The researchers suspect that this includes both the physical work of transporting food and the mental work of deciding between two things.
The Goffin cockatoos (Cacatua goffiniana), native to Indonesia, are extremely intelligent and adaptive animals. For example, you build and use complex tools and make logical decisions. In addition, the birds detect the weight of an object better than primates such as chimpanzees and capuchins, previous studies have shown. But why are cockatoos so good at estimating weight? Could it be because they fly – a notoriously energy-intensive form of locomotion – and transporting a heavy object in flight is a significant additional energy expenditure for the birds?
Cockatoos prefer light objects
A team led by Celestine Adelmant from the University of Oxford has now tested this assumption in various experiments. To do this, the biologists first gave the cockatoos two objects about six centimeters in size that were visually identical but had different weights. The birds received a piece of cashew kernel as a reward if they transported one of the two objects with their beak over a short distance of 1.50 meters between two platforms. In the first test, a bridge connected the platforms so the cockatoos could walk. In the second round there was no bridge, so the birds had to fly to transport the chosen object. Each of the eight cockatoos had a total of twelve trials for transport, six for running and six for walking. The two weights weighed a few dozen grams, but were each adjusted to the individual fitness of the cockatoos.
This showed that the cockatoos recognized the weight difference between the two mini kettlebells and transported the lighter object in 74 percent of cases. Even with a slight weight difference of 30 percent, most cockatoos in the test preferred to carry the lighter dumbbell. The biologists conclude that the cockatoos can also apply their knowledge of weight differences to practical tasks. Contrary to expectations, the cockatoos’ preference for lighter objects was equally pronounced when flying and walking: they chose the heavier dumbbell equally rarely in both test variants. “The birds paid attention to their weight during transport, but it didn’t matter to them whether they had to walk or fly,” reports co-author Antonio Osuna-Mascaró from the University of Veterinary Medicine Vienna. It is still unclear whether this could be due to the unnaturally short transport distance in the experiment.
How do the cockatoos make their decision?
Another result of the experiments: In almost 40 percent of cases, the cockatoos lifted one weight, then put it down and returned to the other. Adelmant and her colleagues report that they repeated this process twice on average before transporting either object. “This switching may reflect metacognitive awareness, suggesting that the birds explore their own knowledge to evaluate both options,” says Osuna-Mascaró. Accordingly, cockatoos sometimes weigh their options before choosing the lighter object. But they don’t always take the time: “These little guys love to do things quickly,” says Osuna-Mascaró. The team suspects that the fact that the cockatoos do not prefer lightweightness more when flying than when walking could also represent a compromise. The cockatoos could weigh up how great the physical effort is when carrying something and how great the mental strain is when making a decision. In this dilemma, the birds apparently occasionally choose the faster option instead of the easier option.
Another possible explanation would be that cockatoos also care about weight distribution. Because flying is a complex process, it could be important how well the transport weight is balanced. However, a follow-up experiment speaks against this, in which the cockatoos showed no discernible preference between two mini dumbbells with different well-balanced weights. The biologists conclude that the total weight rather than the weight distribution is the decisive factor for their transport task.
Energy efficient foraging?
It is still unclear why the weight distribution within the load is irrelevant. A connection with the typical diet of cockatoos would be conceivable: heavier nuts and seeds generally contain more nutrients. However, how the weight is distributed in the nuts and seeds is irrelevant in this regard. “Therefore, birds may not have evolved mechanisms to detect or counteract this cue,” says Adelmant.
But why don’t the birds always choose the heavier dumbbells? “Cockatoos’ preference for lighter objects suggests an energy efficiency strategy that could be crucial to their natural foraging behavior,” says senior author Alice Auersperg from the University of Veterinary Medicine Vienna. Accordingly, it could be less strenuous and therefore more efficient for the cockatoos to transport lighter rather than heavier food, despite its higher nutrient content. In the experiment, however, the reward was always the same and the additional effort of the heavier weight was therefore unnecessary.
“Building on this, future experiments could investigate how these birds handle the transport of tools of different weights and usefulness,” says Auersperg. It is possible that the cockatoos behave similarly to monkeys, which prefer heavier stones when cracking nuts. “Such studies could reveal even more about how birds find the balance between physical effort and cognitive demands in complex tasks,” says the researcher.
Source: University of Veterinary Medicine Vienna, specialist article: Scientific Reports, doi: 10.1038/s41598-024-76104-7