On a visit to the Kgalagadi National Park in May 2022 we were surprised by the size of the flocks at some of the waterholes. Red-billed Queleas, Red-headed Finches and Cape Turtle Doves were abundant, and the sound of thousands of birds flying in and out of the waterhole was particularly noticeable at Urikaruus. It was a visual and aural feast.
Like Common Starlings, the birds flew in synchronised waves. As Lanner Falcons attacked low and fast, thousands of drinking birds would leave in vast flights and then descend on nearby trees where they would cluster in huge numbers. These were mixed-species flocks, which made the spectacle even more interesting. The flocking patterns and noise are known to disorientate and confuse predators, such as Lanner Falcons, giving individual birds a higher chance of survival. However, weaker or younger birds were sometimes stunned or injured in the mêlée. Injured birds would later be eaten by jackals, Secretarybirds or goshawks.
We wondered how each bird got an opportunity to drink. We watched large flocks fly in and saw birds at the bottom drop down for a quick drink before the entire flock rapidly flew off. Do the birds rotate, with those that have had a chance to drink staying at the top and those that have not rotating to the bottom of the flock as they fly into the waterhole? As the birds left the safety of the trees, it looked as if the entire flock left each time, including those that had already drunk.
PETER RYAN responds: It’s unlikely that the birds are taking turns in the sense of any kind of altruistic behaviour. Work done on how birds manage to fly in very large, tight flocks suggests there is no grand design – just birds reacting to the movements of their immediate neighbours.
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