Dear Readers, can I start by saying that this was a fascinating and well-presented talk, with lots of fascinating videos and graphics, and if you have an hour to spare I would hot-foot it over to the LNHS Youtube channel to watch the whole thing. Steve Portugal is such a clear and entertaining speaker that it’s best to get this info direct, but here is my synopsis.
The talk is really about why birds gather in groups, how they behave when they do, and what advantages they gain from their behaviour. There are two main ways of ‘flocking’, and these are dictated largely by size. A bird that is smaller than a black-headed gull is likely to form a ‘cluster’ – we see this in pigeons and starlings and all those other little birds. Any bird larger than this is likely to fly in a V-formation, so that includes cranes, geese, pelicans, flamingoes and, as we’ll see, ibises.
To start with, Portugal looked at birds that fly in a V-formation. Partly this might be because large birds are much less manoeuvrable – a crane has the same turning circle as a jumbo jet, apparently. Other reasons might be:
- the dilution effect – if lots of birds fly together, an individual is less likely to be predated (this applies to cluster flocks too)
- Navigation – older, more experienced birds fly at the front to teach the younger birds behind the route.
- Vision – it’s easier to see the lead bird if you fly in a V formation
- Energetic – birds are able to save energy by flying in this way.
It’s this last point that Portugal is most interested in. When a plane or a bird flies, it pushes the air in front of it out of the way. At the wing-tip something called a wing-tip vortex is created, and this provides an updraft, which makes staying in the air easier. However, most of the air gets pushed down and creates a downdraft, which will push anything following down. It’s this effect that dictates the gap between planes when taking off at an airport, and its the wingtip vortex effect that is thought to be one of the reasons why birds fly in a V formation.
Lest you think that this is all about birds, Portugal explained that aircraft manufacturers are desperate to copy this effect, to save fuel. He showed a short film made by an airline in which a plane takes off from Melbourne and is joined by others from other Australian airports to fly across the Pacific. When the planes join, they get into a V formation, and fly together until they make landfall above the US, at which point the planes peel off to go to their different destinations. However, another film showed a group of small planes trying to do just this, and getting into all kinds of trouble – planes have to get so close together to find the updraft from the wingtip that they risk stalling or tumbling over. It’s thought that only a computer will be able to calculate the manoeuvres required with enough accuracy to avoid disaster.
However, back to the birds. Portugal’s subject study was made possible by the advent of biologgers that are small and light enough to attach to a bird, and also by a study into the Waldrapp Ibis (also known as the Northern Bald Ibis). Historically they were present all through Mediterranean Europe, Northern Africa and the Middle East but, after the recent extinction of the Syrian population, the only wild birds left are in Morocco. This population doesn’t migrate, but it was hoped that they could be trained to return to their old haunts and establish new groups in Europe. To do this, the birds were given a human foster parent, who lived with them for nine months. Then, they were trained to fly after a microlite, and were eventually taught a migration route to Northern Italy.
What Portugal found was that these birds, who had human ‘parents’, automatically formed a V Formation when they flew, at 45 degrees to one another, approximately 1.2 metres apart. This was exactly as predicted by aerodynamic theory, which is based on fixed-wing planes. What the birds did was synchronise their wingbeats naturally to avoid generating turbulence between them. Each bird except the one right at the front rode on the updraft of the bird in front.
The group was dynamic, with no clear leader, though birds did seem to have a preference for their position, be it to the right or left, front or back.
However, the birds noticed how long another bird took at the front of the flock, and would then allow it to take a rest at the back, as if they had an innate sense of fairness.
What happened in the flock also depended on the ‘popularity’ of the individual bird. Portugal defined this as ‘the number of connections and interactions’ that a bird had with other birds. If an ‘unpopular’ bird stopped off for a rest, the others would look round, notice who it was, and then just keep going. If a ‘popular’ bird stopped, however, all the other birds would go down for a rest too. What we think of as ‘leadership’ might just be about a network of relationships instead.
Portugal finished his talk with something a bit closer to home: pigeons. Pigeons are about the maximum size for birds that fly in a cluster, and, unlike V Formation flying, being at the front of the group is good from an aerodynamic point of view, being at the back is bad.
Sadly, in pigeon society the popular/unpopular thing plays out in a different way. Shy pigeons are nearly always at the back. Bold, investigative pigeons are nearly always at the front. And unlike with geese and cranes, that’s the way it stays – if you’re a backmarker, that’s where you’ll stay.
Portugal had his pigeons fly over a number of routes. To start with, the group would be somewhat inefficient, but after a dozen flights they’d have the most direct route mapped, and that would be the one that they’d always follow. However, here’s the rub. After the flock had flown a route over a hundred times, he would take pigeons out for a solo flight. The ones who were always at the front came home pretty directly (though interestingly the flock as a whole always flew faster than a solo bird). But when he released a bird that had been at the back of the flock, they almost always either gave up and went to sit in a tree, or got lost, sometimes for days.
Were they just not paying attention? Or were they so intent on keeping up that they didn’t have the energy to see where they were going? Could they maybe not see the lead bird properly? All very good questions for which we have no answers. But how fascinating! I learned so much from this talk, and in particular I loved the clear structure, which makes it so much easier to take in and to remember – I’ve barely had to look at my notes while I’ve been writing this. Do pop over and have a look. I guarantee that you won’t be disappointed.
Photo One By Myself (Adrian Pingstone). – My own photo, taken with a Nikon D5300 DSLR and Nikon 18-200 mm lens, Public Domain, https://commons.wikimedia.org/w/index.php?curid=71095389
Photo Two By Richard Bartz, Munich aka Makro Freak – Own work, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=3329144