• Sue

Here come the shape shifters



We have a large clump of bamboo. It was here when we arrived, has the potential to be highly invasive and we should have taken it out at once. Instead we left it, as it makes a useful shield agains the north wind. Now not only has it taken on a life of its own, but at this time of year it also offers a home to thousands of starlings who use it as their winter accommodation.


Over the last five or so years we have seen a gradual increase in the number of starlings which appear as if from nowhere and use the bamboo as their night time roost. They arrive at dusk, appearing from all directions, and congregate into large flocks, called murmurations, before settling in the bamboo. They then make a terrific racket for about half an hour before they settle down for the night. In the morning they disappear much more quietly, and without spectacle. I never notice them go.


There is only one night when we have had our sleep disturbed. The starlings were making a fuss so we went outside to see what was going on and a barn owl flew out from the bamboo. It had been in there, helping itself to the contents of nature's larder. The larder's occupants had been objecting.



This barn owl has caught a mouse - not one of our starlings


Some evenings are more spectacular than others, but last night we had a terrific half hour's entertainment. Four of us were eating supper in the garden when they arrived, performed their amazing cabaret and then dived into the bamboo for 20 minutes' squabbling over who was going to sit where before settling down.


So what is going on?


Starlings are partially migratory. In countries such as the UK and France they live happily all year round, but those which live in colder climates migrate when the autumn months arrive. So it is that ours usually arrive in September each year, although this year they started congregating in late August. During the day they spread out around the surrounding countryside, but as dusk approaches they start to congregate around their roosting place. We see rows of them sitting on telegraph wires and can hear them in nearby trees. At some hidden signal they take to the sky in small groups which gradually coalesce into larger ones which are called murmurations. These murmurations create the most extraordinary shapes as they twist and turn, in perfect synchronicity, in the sky above their roosting place. There appear to be no collisions or disharmony and the flock moves as one, gradually getting bigger. Then, at another signal which I can't detect, they plunge into the bamboo to take up roost. Research suggests that to avoid collisions and retain the synchronicity of the murmuration the starlings try to maintain the same distance from their nearest seven or so neighbouring birds. This enables the entire flock to flex and turn as one body. But how they communicate flock-wide signals, such as when to turn or plunge, is a mystery to me.


Here is a link to a National Geographic You tube video of a murmurations - thank fully much bigger than ours:


https://www.youtube.com/watch?v=V4f_1_r80RY


Scientists aren't entirely sure why murmurations occur, but they believe that the purpose of them is to create safety in numbers, in a similar manner to shoals of fish, - it is hard for a predator to pick off one starling from a mass of thousands. It also creates a clear "here we are" signal to other, small groups of starlings, who join the murmuration, both for their own security and to strengthen the flock. Once they are into the night time roosting place, the density of birds means that they can huddle together for warmth and maybe it is also a form of bonding - to create general social adhesion and to spread information - a little bit like bees. When roosting they can pack together densely - with more than 500 per square metre of the roosting site.


This year we have a larger than usual number of starlings and they arrived earlier. Scientists believe that when food is scarce they do create murmurations of larger numbers. This suggests that the very dry summer has resulted in a scarcity of food; something to take account of with garden birds this winter.


Interestingly, despite the fact that we have so many resident starlings I have never (yet) seen them at our bird feeders in the winter. We hardly see them in the garden during the day and I am never really sure when they disappear each year - I just realise, at some point, that they have gone. I need to keep a record. It is a wonderful annual spectacle and, even though our murmurations are small compared to most ( we only have a little patch of bamboo) it is a rare privilege to be able to witness them return to us each year.






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