According to Charles Darwin, helping others just doesn't make sense. Yet we've seemingly seen altruism time and again in the animal kingdom: in primates, in canines, in cetaceans, pinnipeds, even vampire bats. Now, for the first time, it's been demonstrated in birds.
The kind bird is one of the titans of avian intelligence, the African grey parrot (Psittacus erithacus). New experiments have shown these birds happily helping each other acquire treats, without any assumption or anticipation that their altruism will be reciprocated.
"We found that African grey parrots voluntarily and spontaneously help familiar parrots to achieve a goal, without obvious immediate benefit to themselves," explained behavioural biologist Désirée Brucks of the Max Planck Institute for Ornithology.
But the birds take it one step further. Unlike primates, for example, the parrots display no anger or envy if one of their friends receives favourable treatment, instead seeming quite content that good things are happening to a buddy.
Among the bird kingdom, it's the corvids - such as crows and ravens - that are probably the most famed for their wicked smarts, and with very good reason. In fact, corvids have demonstrated skills previously only observed in primates.
However, the researchers said, corvids have failed tests of altruism. But there are other smart birds out there - like parrots. Cockatoos can make their own tools, and have even demonstrated playful creativity. And African grey parrots have proven to be smarter than a human child in some tests.
So, the research team designed a test for altruism, and gave it to two different types of parrots - eight African greys, and six blue-headed macaws (Primolius couloni).
The birds had been previously trained to exchange tokens (metal washers) for treats. This training was refreshed, and the scientists assessed their subjects' relationships with other birds of their species. Each bird was tested with one bird with whom they had a close bond, and a second bird with a less close bond.
The birds were then placed in a clear perspex enclosure, with a dividing wall between them. The front of the box had holes through which items could be exchanged with a human; and the dividing wall between the birds also had a hole, through which the two birds could also exchange items.
All the birds quickly understood the concept of swapping the washer for a piece of walnut, and were able to do so. But, when only one of two birds was given tokens, only the African grey parrots, not the macaws, also deliberately gave tokens to their buddies.
"Remarkably, African grey parrots were intrinsically motivated to help others, even if the other individual was not their friend, so they behaved very 'prosocially,'" said zoologist Auguste von Bayern of Oxford University.
"It surprised us that 7 out of 8 African grey parrots provided their partner with tokens spontaneously - in their very first trial - thus without having experienced the social setting of this task before and without knowing that they would be tested in the other role later on. Therefore, the parrots provided help without gaining any immediate benefits and seemingly without expecting reciprocation in return."
In all, they voluntarily gave other African grey parrots 157 out of 320 tokens - nearly half. And, interestingly, although they passed tokens regardless of their social bond, they did give more tokens to birds with whom they shared a close bond.
The macaws, by contrast, rarely passed their tokens through to the other parrot. If they did, they dropped it through the hole; and they did it more often when the human experimenter was present. This led the scientists to believe the macaws were trying to pass the token to the human, not their buddy.
The difference could be due to social differences between the species in the wild, but there was one more interesting thing. In a separate recent study, the researchers showed that, when an African grey parrot sees a friend getting a better treat, they didn't seem particularly bothered. This is in contrast to animals such as chimpanzees, who tend to get riled up about it.
According to von Bayern, this could be because the parrots monogamously mate for life.
"Given that parrots are so closely bonded with a single individual and thus so mutually interdependent, it does not make any difference if one of them gets a better pay-off once in a while," she said.
"What counts is that together, they function as a unit that can achieve much more than each of them on their own (in addition to raising their joint offspring). This is probably why parrots are much more tolerant towards unequal treatment than species that are not long-term monogamous, while still being excellent cooperators."
The research has been published in Current Biology.