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Flocking Behaviour of Red-billed Quelea

This diary entry took place at Ongava Tented Camp, Etosha National Park, Namibia

From Ongava Game Reserve, daily nature drives into Etosha National Park always deliver something interesting. A stop at Aus waterhole in late November 2011 produced an avian spectacle with a difference. The surrounding mopane scrubland was alive with the chattering calls of the sub-Saharan Red-billed Quelea (Quelea quelea) and small flocks of these birds were whizzing past us continuously.

The waterhole itself was fairly quiet - the only activity, apart from the constant quelea fly-bys, was a pair of Red-billed Teal on the water and some black-faced impala drinking nervously. Then, just off to the west of the waterhole, a large 'swooshing' noise drew our attention. The queleas were actively congregating into a far larger single flock and began flying around in a coordinated aerial display that was amazing to observe. The group manoeuvred as a single unit, changing direction instantaneously. More birds continued to join, the flock now comprising thousands of birds, a living entity with a mind of its own, changing shape and size with each turn. The birds then descended en masse to the edge of the waterhole, the flock so dense at times that the surroundings were hardly visible. The teal and impala could not even be seen any longer! Meanwhile, birds joined and left the flock fairly quickly after a brief drink at the water's edge. A few minutes later, the flock started to break up again and things returned to normal.

One possible reason for the flocking behaviour we saw could be reduction of the individual birds' risk of predation, literally swamping would-be predators (a pivotal theory hypothesised by John Lazarus in 1979). As the flock size increases they seem to spend less time being vigilant for predators and more time feeding.

The random movements of the bunched up flock could also make it hard for predatory birds to hone in on a single individual. This may certainly have been the case here, as a Lanner Falcon was actively hunting in the area. What left me a little puzzled though was what triggers these birds to flock in such a manner? Certain researchers have even conjectured that electromagnetic communication could be involved in preventing mid-air collisions between the flocking birds.

"Allelomimetic behaviour" perhaps best describes how a flock of birds fly in unison. Also seen in schools of fish, it is a phenomenon that where one bird goes, so does the flock. It is also referred to as 'wave manoeuvre', just like humans do 'the wave' at a cricket match. Due to the extremely rapid reaction times of the birds in the flock, it looks instantaneous. There is no overall leader; instead the flock's movements are determined by the moment-by-moment decisions of individual birds. Different birds are in front of the flock every time it changes direction.

This cohesive flocking behaviour is also seen when queleas forage - they then also come together in huge swarms and work cooperatively in search of food sources. For farmers, who perhaps do not view these avian aggregations with the same awe as we birders do, this is like something out of Alfred Hitchcock's thriller The Birds! As specialised seed-eaters they can wreak havoc on farmlands, decimating crops in no time. After a successful search, they descend on a food source in a similar way to that which we witnessed at Aus waterhole.

As the world's most abundant bird species, with a breeding population of over 1 billion birds in Africa, these quelea formations are amongst the most fascinating flocking phenomena in nature. There is no doubt that these aerial manoeuvres require remarkable skill and coordination.



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