Crows are capable of exercising volitional control over their calls—emitting or inhibiting the vocalisations at will—according to the situation, says a study published in the science journal PLOS Biology.
The findings show that trained carrion crows (Corvus corone)—common crow found in most parts of the world— have goal directed control over their calls, suggesting that songbirds could have cognitive control over their vocalisations. Songbirds are well-known for their acoustically elaborate songs.
Katharina Brecht of the University of Tubingen, Germany, and colleagues, tested the idea that songbirds could be deliberately controlling their calls as opposed to the calls being instinctive responses to food, mates, or predators.
In the experiment, three male carrion crows learned to emit calls in response to a visual cue of coloured squares with no inherent meaning, which the team named go-cues', and to withhold calls in response to another cue.
Then, two of the crows were trained on a task with the cue colours reversed. Additionally, in another trial dubbed no-go cues, the crows were rewarded for withholding vocalisations to yet another cue.
The calls in response to the detection of the go-cue were precisely timed, and highly reliable in all the crows. The crows also quickly learned to withhold calls in no go-trials—showing that they were not singing in anticipation of a food reward in the go-trials, the study said.
"Our study shows that crows can be taught to control their vocalisations, just like primates can, and that their vocalisations are not just a reflexive response, note the researchers.
This finding not only demonstrates once again the cognitive sophistication of the birds of the crow family, it also advances our understanding of the evolution of vocal control."
The authors emphasise that further work is needed to evaluate the neurobiological basis of such cognitive vocal control in birds. Until then, one may not be able to conclude that the crows consciously control the observed variability in calls, as they may also be driven by involuntary neurological mechanisms, the study said.
(With inputs from PTI)