Posted on behalf of Chloe McIvor.
Most of us would admit that we’ve been amused by a parrot’s vocal talent at some point in our lives. Though entertaining, it’s perhaps hard to imagine that an ability to repeat “Pretty Polly” on demand is of much use to a parrot in the wild. But parrots don’t just mimic humans; their ability to imitate is likely to be important for maintaining their dynamic social structures. Cornell University scientists have found that parent birds pass on learned vocal signatures, a bit like human names, to their offspring. This research is the first evidence of how parrots transmit a socially acquired trait in the wild.
Vocal signatures are used to recognise individuals in a population and so far only parrots, dolphins and humans have been shown to imitate the signatures of others throughout their lives. “When one parrot imitates the signature call of another, it gets their attention and opens the door to further, more complex exchanges of information,” explains Karl Berg, a behavioural ecologist who conducted the study, published today in Proceedings of the Royal Society B.
This ability could be linked to the fact that parrots have very “fluid” social systems. Wild parrots exhibit a fission-fusion type of population dynamic which means that flocks frequently break up and change. Therefore an ability to learn signatures and link them to the new individuals would be helpful. Similarities can be seen in human populations “Little in our society would function without the use of our own ‘names’ and the ability to ‘imitate’ names of others,” says Berg.
Previous studies on captive birds showed that adults have signature calls that are used to recognise individuals, and suggested that these are assigned by parents to their offspring. Berg and his team wanted to find out whether this was the case in the wild and did so by monitoring wild green-rumped parrotlets in Venezuala. In order to discern whether signatures were parent assigned they need to eliminate two alternative possible explanations for observations made in captive birds. One possibility being that the juveniles acquire their own signature calls and then parents and siblings learn these calls to attract their attention, and the other being that parents provide a range of vocal labels to their offspring until one is acquired, rather than directly labelling them.
The researchers did this by monitoring the contact calls made within the video-rigged nests and compared the calls made early in the development of the chicks with those made later on. (see video below)
They found that the adults made contact calls before the nestlings were able to call themselves and that, once grown-up, they emulated these calls. The researchers also found that this happened with nestlings raised by foster parents, demonstrating that it is a learned social trait rather than one of biological inheritance.
Scientists have long been interested in how knowledge gained from birdsong might be applied to understanding human speech but less attention has been paid to parrot calls. This new research suggests that more parallels might be drawn between parrot calls and human speech than previously thought. Berg suggests that this could be related to the fact that parrots, like humans, take a long time to develop “Parrots do seem to be unique among birds in that they take a long time to mature. Because these signature calls appear to function like names, and are first learned from parents, it suggests an alternative model system for understanding infants’ acquisition of human speech.”
It seems clear there’s more to parrot learning than is implied by their famed ability to copy silly phrases.
Image: Green-rumped parrotlets / Nicholas Sly