“I vote for the departure!” In the colonies of our native jackdaws, there is apparently a loud vote in the morning about when the communities of hundreds of birds should leave. This emerges from an examination of the jackdaw’s cry at dawn. In addition, the researchers were able to persuade the “feathered democrats” to start early by using “acoustic election fraud”.
A petite figure, silvery-blue eyes and a loud voice: these are the hallmarks of our smallest native representative of the corvids. Anyone who has jackdaws (Corvus monedula) as neighbors knows that these birds, which live in social groups, are extremely “chatty”. Sometimes the question really arises as to what they have to tell each other or are currently concocting. Studies have already confirmed that jackdaws convey complex information through their sounds. The current study by researchers led by Alex Dibnah from the University of Exeter now shows that the birds can apparently also literally vote.
Coordinated departures
The team focused on a typical group behavior of jackdaws in the winter months: After they have spent the night in the trees, the communities of sometimes more than a thousand birds usually start their “day’s work” at the same time. The communities are not only large, but also include individuals of different ages, genders and different subgroups. “Each jackdaw actually has a slightly different preference for when they want to fly, based on factors like their size and how hungry they are,” says Dibnah. “However, finding a consensus seems sensible. Because leaving the roost together offers various advantages, including protection against birds of prey and access to information about food sources,” explains the researcher.
To investigate suspicions that some sort of voting led to the collective departure, Dibnah and his colleagues recorded extensive audio and video footage of six different jackdaw roost sites in Cornwall over the winter months. In this way, the scientists were able to precisely document the course of the take-offs and examine to what extent the screaming in the night colonies, comprising up to around 1500 individuals, changed before the mass take-offs.
First of all, it turned out that the birds usually set off together – hundreds of individuals took to the skies at a distance of only about four seconds from each other. These departures took place between 45 minutes before sunrise and 15 minutes after. The researchers found that rain and heavy cloud tended to delay departure. As can be seen from the evaluations of the sound recordings, there was always a significant increase in communal vocal violence before the departure. This reflected that more individuals were “speaking up”. The researchers interpreted this as an indication that the jackdaws were literally voicing to allow synchronized departure of the community. It was also remarkable that in the few cases in which the intensity of the calls did not increase sufficiently, the birds did not seem to reach consensus. As a result, they flew off “drop by drop” rather than all at once.
Experimental “electoral fraud”
But until then it remained unclear what is cause and effect, so the researchers carried out a clarifying experiment: they placed loudspeakers in the sleeping trees of one of the jackdaw communities, over which they played recordings of calls in the morning. It turned out that by artificially increasing the power of their voices, the birds broke up about seven minutes earlier on average. However, when the researchers played back wind noise to check, this was not the case. Thus, it was confirmed: “Through their calls, jackdaws appear to effectively signal their readiness to depart and provide the community with a means to reach a consensus so that they can conduct coherent, common departures from the roost,” the researchers write.
“There is evidence that, like humans, animals can use group decision-making to overcome individual differences and achieve a kind of ‘democratic’ consensus,” said senior author Alex Thornton of the University of Exeter. He and his colleagues now want to stay true to this exciting research topic: They plan to continue listening carefully to the clever corvids in order to uncover more details of their complex communication system.
Source: Cell Press, University of Exeter, Article: Current Biology, doi: 10.1016/j.cub.2022.04.032
Video: A community of jackdaws starts in the association. © Dibnah et al./Current Biology