Murmuration

On recent evenings, I've watched starlings preparing to roost for the night. Their havens are three specific trees in the old grounds of Kenilworth Priory - now a park. The birds - in groups of around 30 - return from the fields just before sunset, the growing murmuration (for that's the term) hypnotically swirling, individual groups merging and coalescing in a rythmic and seemless cloud of birds, some cosmic air traffic controller ensuring that not a feather touches. The starlings chatter as they mingle in dance, the volume of twittering joyously increasing as each new group joins the swell. When all are assembled, the entire flock descends to the trees. I wonder if each bird has its allocated place? The starlings certainly congregate for warmth and security during the winter months. But, if the excited murmurings are anything to go by, surely for the joy of companionship as well?  

And here's a picture of the roosts and the murmuration.