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Nature’s marvel: Thousands of Jackdaw birds decide by voice vote to fly out at same time after night’s rest

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Jackdaw birds communicate with each other to reach a group decision to time their take-off in the morning (Pics. Courtesy Twitter/@MyBirdBeeGarden)

Collective decisions in a group are useful and remarkable, more so since they are not easy to arrive at. Yet, it is evident in birds like jackdaws. These birds are found in Europe, North Africa and Western Asia.

It is quite a sight to see these birds numbering in thousands take off in unison around sunrise. Leaving their roost all together they create an enchanting huge picture in the sky. A study, according to a report in smithsonianmag.com says that jackdaws use vocal communication to decide on when to take off by voting.

The details of this study were published in Current Biology of May 2022. The research also said that the calls were distinctive and sounded either “tchaw, tchaw” or “tchack, tchack”.

Talking about their calls, Alex Thornton told media: “When a bird calls, it’s casting a vote or signalling it wants to leave.” Thornton is an ecologist at the University of Exeter, U.K.

According to Alex Dibnah, a University of Exeter researcher who led the study when the birds’ calling finally comes to a “sufficient level”, the group takes off.

Describing the scene of jackdaws taking to the sky, Thornton told New Scientist: “They all leave together, which is a really striking sight. The sky just suddenly fills with black birds. It’s like a black snowstorm. At first you just get a few calls, then more and more birds join in and it builds and it builds, and the steeper that increase, the earlier they leave.”

Jackdaws belong to the family called Corvidae. In this fold are included birds like ravens, crows, magpies and jays. What is indeed remarkable about this family of birds is their complex behaviour including sharing of food which is not found even among primates.

For their research the scientist gathered the footage and audio recording of six jackdaw roosts in the United Kingdom’s Cornwall spread over two winters. The researchers observed that the birds take off in large numbers in a timeframe which extends from 45 minutes before sunrise and 15 minutes after sunrise. Once the collective noise is at its highest, the birds decide to leave. On an average within five seconds of each other, all the birds left.

By playing the recording of calls, the researchers were able to delay the departure of the birds by six minutes yet playing the sound of other noises had no effect on them. This proved that they responded only to the sound of birdcall.

It is not always possible for a large group to reach a collective decision. This happens with the jackdaws too and in that scenario, they fly off in smaller groups.

Talking about their departure Dibnah in a statement said: “After roosting in a large group at night, each jackdaw will have a slightly different preference about when they want to leave, based on factors like their size and hunger. However, it’s useful to reach a consensus. Leaving the roost together has various benefits, including safety from predators and access to information such as where to find food.”

With the human activities increasing and becoming noisier, the communication between the jackdaws is being disrupted and this interferes in the interaction between the jackdaws.

Highlighting this aspect, Thornton in the statement said: “Our findings provide further evidence that vocalizations are really fundamental in allowing some species to reach group decisions – so we need to investigate what happens when we as humans create noise pollution that might influence how information spreads through these social groups. The next stage of our research will look into this.”