Cornell University researchers have found that parent parrots in the wild 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. Results of the study appear online July 13, 2011 in Proceedings of the Royal Society B.
Populations use vocal signatures to recognise individuals. So far, only parrots, dolphins and humans are known to imitate the signatures of others throughout their lives. Karl Berg, a behavioral ecologist who conducted the study, said:
When one parrot imitates the signature call of another, it gets their attention and opens the door to further, more complex exchanges of information.
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 are evident in human populations. Berg explained:
Little in our society would function without the use of our own “names” and the ability to “imitate” names of others.
Previous studies on captive birds showed that adults have signature calls that are used to recognize individuals. The studies suggested that parents assign these to their offspring. Berg and his team wanted to find out whether this was the case in the wild. They did so by monitoring wild green-rumped parrotlets in Venezuela. In order to discern whether signatures were parent-assigned, they needed to eliminate two possible explanations for observations made in captive birds: 1) juveniles acquire their own signature calls, and then parents and siblings learn these calls to attract their attention and 2) parents provide a range of vocal labels to their offspring until one is acquired, rather than directly labelling them.
The researchers carried out their study by monitoring the contact calls made within the video-rigged nests and comparing the calls made to new chicks with those made when the chicks grew up.
They found that the adults made contact calls before the nestlings were able to make calls themselves and that, once grown up, the offspring 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.
This new research suggests that more parallels might be drawn between parrot calls and human speech than previously thought. Berg suggests 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.
Bottom line: Behavioral ecologists from Cornell, studying green-rumped parrotlets in Venezuela, determined that parents give offspring individual names, or vocal signatures, which the chicks keep as they mature. Results of the study appear online July 13, 2011 in Proceedings of the Royal Society B.