There’s a famous nursery rhyme about magpies. If you see one, the rhyme says, you can expect sorrow in your future. Two bring joy, “three for a girl, four for a boy. Five for silver, six for gold, seven for a secret, never to be told.” A new study from scientists at Great Britain’s University of Exeter and the University of Western Australia reveals a special secret about large groups of magpies, though it’s more of a boon for the birds than their spotters. Growing up in a large social group seems to make wild Australian magpies more intelligent, they say, with birds scoring better on four separate intelligence tests when they’ve been raised in sizable broods.
Researchers in Perth, Australia, examined 14 different groups of wild magpies. These birds live in stable social groups akin to families, with multiple generations often occupying the same territory for years at a time. Some of these groups had just three birds, while others were a veritable flock of 12.
One test measured self-control—birds had to stop themselves from pecking directly at a snack in a transparent tube, and instead go around to the side where the tube was open to acquire their grub. Two of the cognitive tests taught the birds to associate a particular color with a food treat. In the final test, birds had to remember where a lump of mozzarella had been hidden in a grid. Time and time again, the birds from larger groups seemed to perform better at these tests. And the benefits of coming from a large family kicked in early: A link between group size and intelligence emerged when the birds were just six months old.
Why should this be the case? People have often wondered whether living in a complex social group drives cognitive evolution. Co-existing with others can be arduous—you have to remember who everybody is, get along with them, and understand the intricacies of belonging to a large community. Evidence for this was often contentious, Ben Ashton, the lead researcher in the study, said. But, in the case of these wild magpies, “our results suggest that the social environment plays a key role in the development of cognition,” he said, in a statement. And for female magpies in particular, not being featherbrained is a particular asset. “They also suggest that females who do well in cognitive tasks have more offspring, indicating there is the potential for natural selection to act on cognition. Together, these results support the idea that the social environment plays an important role in cognitive evolution.”